Post by: Wayne Parham on July 23, 2007, 02:43:22 PM
This year's Prosound Shooutout will be held at the Tulsa Raceway on October 19th, 2007. This is our third year in a row, and the venue is excellent so we expect turnout to be good. We've received a lot of attention by the quality of data we've gathered, which has given us some traction. All the big names will be there this year, so be sure to come out to the track and join us!
Post by: Jeff Permanian on July 23, 2007, 04:20:37 PM
Post by: larry gallant on July 23, 2007, 09:51:37 PM
http://www.growlersound.com/about_us.htm
Larry
Post by: Wayne Parham on July 23, 2007, 09:52:01 PM
You betcha. We'll put you on the list. We'll update the Prosound Shootout website with links all the exhibitors that plan to attend soon.
Let me know if you need any help with directions, finding a hotel, etc. I look forward to hanging out with you, Jeff. See you there!
Post by: Scott Waldy on July 23, 2007, 11:22:09 PM
| larry gallant wrote on Mon, 23 July 2007 19:51 |
Jeff Growler is perhaps a poor name choice for your sub. http://www.growlersound.com/about_us.htm Larry |
Larry, there is an somewhat of an old saying here on the lab for most Newbies....
"Read more, Post Less"
Maybe you ought to adhere to that for a while.
Open mouth and insert foot. Taste the shit you just stepped in? You ought to.
Post by: Michael 'Bink' Knowles on July 24, 2007, 12:49:51 AM
Like water off a duck...
-Bink (Ohmmmmmmm)
Post by: Scott Waldy on July 24, 2007, 04:47:08 PM
| Scott Waldy wrote on Mon, 23 July 2007 21:22 | ||
Larry, there is an somewhat of an old saying here on the lab for most Newbies.... "Read more, Post Less" Maybe you ought to adhere to that for a while. Open mouth and insert foot. Taste the shit you just stepped in? You ought to. |
| Quote: |
Dude, time out. You gotta have thick skin in this biz... If Larry thinks Growler is a bad name just because a production company half the world away shares the name then so be it. No need to get so harsh. I'm sure Jeff Permanian can roll with the punch and keep going. Like water off a duck... -Bink (Ohmmmmmmm) |
My apologies, Larry.
Bink is right, I jumped the gun and was a bit harsh.Jeff has a very good rep around here and has a great product. I just don't like it when someone starts spouting what I feel is shit about someone or something I respect.
My apologies once again.
Scott "Where's my Prozac?" Waldy
Post by: Dave Rickard on July 24, 2007, 06:19:57 PM
| larry gallant wrote on Mon, 23 July 2007 19:51 |
Jeff Growler is perhaps a poor name choice for your sub. http://www.growlersound.com/about_us.htm Larry |
Hi Larry,
1. Growler Sound's speaker line is named the "Conception" series. It could also be considered a poor name choice, especially for certain types of shows.. .
2. When I chose my company name, I confess I didn't see if I would be stepping on anyone's toes in INDIA.
http://www.growlersound.com/contact_us.htm
Post by: larry gallant on July 24, 2007, 08:00:06 PM
I was just pointing out,after hearing of growlers and doing a google search,the Indian co came up and I assumed growlers came from India.It is not good promo if your product name pops up on a search on some other web site.
To get back to the purpose of the thread,Pro sound shootout,I wonder if Danley Labs or servo will be there?
Larry
Post by: Ivan Beaver on July 24, 2007, 08:56:14 PM
Post by: Michael 'Bink' Knowles on July 24, 2007, 09:55:35 PM
| Ivan Beaver wrote on Tue, 24 July 2007 17:56 |
Servo drive is for all intensive purposes a "dead" company |
Intents and purposes... what do you mean by 'dead'? Who's still there? A half time accountant and a warehouse guy? A lawyer who bills a few hours a month? Many possible of shades of 'dead' (pun intended.)
-Bink
Post by: Ivan Beaver on July 24, 2007, 10:35:19 PM
We help out where we can-even though the products that need fixing are not ours. Maybe when they decide to step up, they will remember what we did for them.
Sorry for the spelling-English was not my best subject
.
Post by: Jeff Permanian on July 24, 2007, 10:42:07 PM
| Michael 'Bink' Knowles wrote on Tue, 24 July 2007 20:55 |
Intents and purposes... what do you mean by 'dead'? Who's still there? A half time accountant and a warehouse guy? A lawyer who bills a few hours a month? Many possible of shades of 'dead' (pun intended.) -Bink |
Your giving them way too much credit.
Post by: Jeff Permanian on July 24, 2007, 10:51:07 PM
| larry gallant wrote on Tue, 24 July 2007 19:00 |
Boy,You guys can be harsh on a newbe. |
Sorry Larry, come out to the shootout, I'll get you a few beers.
Post by: Bob Kenton on July 25, 2007, 12:14:10 AM
| Jeff Permanian wrote on Wed, 25 July 2007 03:51 | ||
Sorry Larry, come out to the shootout, I'll get you a few beers. |
Will any of your top boxes (mid/hi) be there?
Post by: Dave Rickard on July 25, 2007, 02:41:34 AM
| larry gallant wrote on Tue, 24 July 2007 18:00 |
Boy,You guys can be harsh on a newbe.I felt really bad posting. I was just pointing out,after hearing of growlers and doing a google search,the Indian co came up and I assumed growlers came from India.It is not good promo if your product name pops up on a search on some other web site. To get back to the purpose of the thread,Pro sound shootout,I wonder if Danley Labs or servo will be there? Larry |
No worries, Larry. Welcome to the LAB.
Post by: Jeff Permanian on July 25, 2007, 10:10:56 AM
| Bob Kenton wrote on Tue, 24 July 2007 23:14 |
Will any of your top boxes (mid/hi) be there? |
I have no problem with that but I think its more up to Wayne.
Post by: Wayne Parham on July 25, 2007, 11:47:19 PM
By all means, bring your top boxes. We are going to measure first and then listen. Subs don't sound like much by themselves.
Post by: Pascal Pincosy on July 31, 2007, 07:03:02 PM
Post by: John Roberts {JR} on July 31, 2007, 08:34:27 PM
| Pascal Pincosy wrote on Tue, 31 July 2007 18:03 |
What's the plan for taking measurements this year? I'd like to see someone who is not affiliated with a manufacturer at the controls this year. |
I like to give them the benefit of the doubt, but with two (or more) we could A) know what and how to measure, and B) keep each other honest.
I suspect if we came up with some pre-discussion of what is to be measured, and saved raw data, we should be able to parse to our own satisfaction, later.
Trust but verify...
JR
Post by: Wayne Parham on July 31, 2007, 09:31:08 PM
| Pascal Pincosy wrote on Tue, 31 July 2007 18:03 |
What's the plan for taking measurements this year? I'd like to see someone who is not affiliated with a manufacturer at the controls this year. |
Me too, absolutely. We had hoped to get one of the forum regulars that was unaffiliated with any manufacturer to perform the measurements at past Prosound Shootouts in 2005 and 2006. When that couldn't be arranged, all the exhibitors discussed the problem of who would do it and we agreed to self-police. It really wasn't a problem, but it is more objective if an outside party runs the show. It's also allows the exhibitors to focus on setup rather than to divide their time between that and taking measurements.
We did have a formal test plan that worked pretty well for us.
Post by: Ivan Beaver on August 01, 2007, 05:36:10 PM
This is derived from the shootout in NYC in Jan.
Since you are limited on time-you really need to make the most of it and make it enjoyable for those who have made the effort to attend.
While this was a great time to "mix it up" I think a lot of the people got tired of all the testing. Mark was way to busy being sure to get it right and fair. He had little time to mingle, whfcih I am sure he would have liked to do more of.
My suggestions.
Forget impedance. There is no such thing as a 1 watt input anyway as the impedance varies with freq. Just accept the manufacturers ratings. Use a standard of 2.83V (2.828 to be exact
) as a reference and let the people viewing "determine" what they feel the wattage is at any particular point on the curve.Just run a single test 28.28V (100watts for 8 ohms) and measure at 10 M. This is the Danley standard so the cabinet frontal area will not affect the measurement any and 100 watts on a swept sine wave to actually get some driver a little into power compression and is more realistic of actual levels than 1 watt. It will back calculate to 1W/1M for reference (@8 ohms)
If a cabinet is rated at 4 ohms, then just subtract 3dB from whatever freq you are looking at to derive the sensitivity.
I don't think you need 3 measurements that agree to have accurate data. If you do, then you need a different analyser, because the one you are trying to use is obviously NOT accurate and cannot be trusted from loudspeaker to loudspeaker.
I suggest a TEF. It is rock solid and if setup properly-the output level will not vary and can be easily calibrated with a calibrator for the best accuracy, not relying on "preset" data for calibration.
There is no reson to measure the amplifier you are using-if you EVEN think that there would be anything there that would affect the data, then you need a different-better quaily amplifier.
Distortion measurements can have some meaning, but most people would rather trust their ears. I would rather spend the time listening to different cabinets than to be measuring distortion.
A really good idea is to use a speaker level switcher to switch between cabinets so side by side comparisons can be made. It is often quite difficult to listen to a loudspeaker and then listen to another sevral minutes later and try to come to any real conclusions about the differences.
Danley uses a 6 channel unit that I built that shorts the unused outputs when not being used so the side by side cabinets do not interfer with each other (much).
As far as who is doing the testing-as long as it is done fair and NOTHING changes from test to test and with a qualified measurement system, then I have no problem with whoever drives. I know the idea is that a manufacturer could "cheat" a little, but if they did, they (and their product/company) would never live it down and would be ridiculed and not trusted with every post they would make here. To me it would simple be to much of a gamble to take-just to fudge some data.
What I did at NY was to get Mark to give me the raw data he had saved, on my stick, so if he tried (which I know he wouldn't) to manipulate the data, it would be different than mine, therefore causing problems/issues with the procedure.
Let the data and the cabinets stand for themselves and do a LOT more listening. At NY we had the whole 2nd day for listening-and I wish we could have done some side by side tests, but the space restrictions made it really hard, but you do not have that problem and product can be more quickly moved in and out of the testing area.
Good luck with the shootout.
PS Be sure sure to get ahold of a BIG amplifier, you might need it for some of the cabinets.
Post by: Wayne Parham on August 01, 2007, 08:35:54 PM
Good suggestions, Ivan, thanks. I agree with what you've said.
| Ivan Beaver wrote on Wed, 01 August 2007 16:36 |
Since you are limited on time-you really need to make the most of it and make it enjoyable for those who have made the effort to attend. |
That's for sure. I've done a couple of these already and time is short during the event.
| Ivan Beaver wrote on Wed, 01 August 2007 16:36 |
Forget impedance. There is no such thing as a 1 watt input anyway as the impedance varies with freq. Just accept the manufacturers ratings. Use a standard of 2.83V (2.828 to be exact ) as a reference and let the people viewing "determine" what they feel the wattage is at any particular point on the curve. |
That might be a good idea. We measured every speaker with 28.3v at 10 meters. I'm pretty happy with that dataset. But I do like to have different power levels too, because many speakers change characteristics at high power levels. The heat makes electro-mechanical parameters shift, and some speakers start to get peaky on the bottom end as a result. We can also check distortion at these different power levels too, which is something I think most people want to know.
The impedance sweep is actually very easy. Once we have it, a quick couple of buttons of the calculator tell you the voltage required to get 100 watts, 200 watts, 400 watts, 800 watts, and so on. It's just not that much trouble and gives us some valuable data.
Then again, even a quick test takes time, and a bunch of quick tests make a long day. So we may be better served doing fewer tests. Maybe one at 28.3v and another at say 500 watts and another at 1000 watts or something like that.
| Ivan Beaver wrote on Wed, 01 August 2007 16:36 |
I don't think you need 3 measurements that agree to have accurate data. If you do, then you need a different analyser, because the one you are trying to use is obviously NOT accurate and cannot be trusted from loudspeaker to loudspeaker. |
Absolutely. I've seen some systems that I wouldn't trust without multiple dataset agreement. But the LMS system is calibrated and is rock solid. There is no need for three sweeps.
| Ivan Beaver wrote on Wed, 01 August 2007 16:36 |
I suggest a TEF. It is rock solid and if setup properly-the output level will not vary and can be easily calibrated with a calibrator for the best accuracy, not relying on "preset" data for calibration. |
I personally like LMS. It has worked very well for me. But TEF would probably be great too. I've always heard good things about it. I don't want any of us to feel like we've been forced to use a system dictated to us though. The group must be comfortable, not just one or two vocal participants.
I think the measurement system decision will likely be dictated by availability and familiarity. I am thinking that probably with this bunch of folks, we are going to need to be very careful with each person's comfort level. We would be best served with measurements made by an independent third party, someone we all trust. But whether that is possible or not has yet to be seen. One thing for sure, I don't want anyone there to be uncomfortable with the quality of measurements or the person performing and storing them. I personally do not want any massaging of data, including smoothing. I want the datasets to be published exactly as they are captured. Scaling should be the same for all published response graphs too.
| Ivan Beaver wrote on Wed, 01 August 2007 16:36 |
There is no reson to measure the amplifier you are using-if you EVEN think that there would be anything there that would affect the data, then you need a different-better quaily amplifier. |
We've never had trouble with this.
| Ivan Beaver wrote on Wed, 01 August 2007 16:36 |
Distortion measurements can have some meaning, but most people would rather trust their ears. I would rather spend the time listening to different cabinets than to be measuring distortion. |
Not me. I want distortion graphs. One of the biggest differences between direct radiators and horns is their distortion characteristics. Horns have different distortion characteristics too. I think it is interesting to see the trends as power levels are increased too.
| Ivan Beaver wrote on Wed, 01 August 2007 16:36 |
As far as who is doing the testing-as long as it is done fair and NOTHING changes from test to test and with a qualified measurement system, then I have no problem with whoever drives. I know the idea is that a manufacturer could "cheat" a little, but if they did, they (and their product/company) would never live it down and would be ridiculed and not trusted with every post they would make here. To me it would simple be to much of a gamble to take-just to fudge some data. |
I agree, but only if everyone present respects one another and are pretty familiar and friendly towards one another. I think that's the way things should be and hopefully will get to be. But I also think that thre are some smouldering resentments and trust issues between some of the guys that might consider coming.
I'm not just talking about some of the more vocal guys you might expect to be mistrustful, I'm also talking about people that have been publically quiet so they didn't get attacked by others or just generally to keep from rocking any boats. I'd like everyone to feel comfortable and respected, not bullied or badgered. I think that's possible. At least, I hope so.
| Ivan Beaver wrote on Wed, 01 August 2007 16:36 |
What I did at NY was to get Mark to give me the raw data he had saved, on my stick, so if he tried (which I know he wouldn't) to manipulate the data, it would be different than mine, therefore causing problems/issues with the procedure. |
Please don't take this wrong. You're trying to be helpful, and I really appreciate that. I think you have an olive branch in your hand, and I do too. So please just take this statement as objectively as possible.
You and Mark Seaton are both personal friends and business associates with Tom Danley. The fact that the data was gathered, organized, processed and published by you and Tom made some people pretty uncomfortable. They told me so.
Again, please don't take that wrong. I saw what you guys did and I could tell you were trying to be fair. But please understand that it's the same thing as if Danley had to trust measurements I made, processed and published. He has been pretty vocal that he would be uncomfortable with that. I understand, and I don't expect him to be forced to accept a situation that makes him uncomfortable either.
We'll need to work in a spirit of understanding and cooperation to find and agree on methods that everyone is comfortable with.
Post by: Michael Hedden Jr. on August 01, 2007, 10:16:15 PM
Interesting that after the NY event there was quite a bit of folks asking for the data to be published. Mark Seaton had already bitten off way more than he wanted to chew and wasn't going to waste any more time with it. We waited several weeks and when nothing was done we published the data both organized and raw and put it up for peer review on the Danley site.
Tom spent several hours of his time putting that data together so folks that didn't own TEF could see the data. If anyone has an issue with Tom Danley's credibility I'd love to hear about it.
The bigger issue we are dealing with is a very niche subject for the majority of our industry. I've worked with TEF workshops around the country and you'll get maybe 30 folks to show up, it just isn't interesting to the majority of the industry.
Of the folks that are interested, few own serious measurement systems or are in a work environment that allows daily use of the systems which is the only way to develop aptitude on how to properly apply the systems.
Ivan Beaver is a dear friend and it has been my great pleasure to work with him for years. Mark Seaton is also a good friend but doesn't work in any capacity with Danley Sound Labs. Both Ivan and Mark are in the small minority of folks with the technical chops to do measurements right and you'll have a very difficult time finding their equals much less superiors.
Peer review is a way to insure integrity but most of the measurement Jedi's I know are too busy doing their own thing.
Three of them participated in some capacity with the NY shoot out and the response has been tepid at best. What is the incentive of them or others, especially without ties to manufacturers participating in more?
Mike Hedden
Danley Sound Labs, Inc.
Post by: John Roberts {JR} on August 01, 2007, 11:36:42 PM
good luck...
JR.
Post by: Tim Padrick on August 02, 2007, 12:05:57 AM
| Ivan Beaver wrote on Wed, 01 August 2007 16:36 |
A really good idea is to use a speaker level switcher to switch between cabinets so side by side comparisons can be made. It is often quite difficult to listen to a loudspeaker and then listen to another several minutes later and try to come to any real conclusions about the differences. |
I find "immediate switching" comparisons to be much less telling than listening to 30 seconds of music, making the switch, and listening to another 30 seconds of music. As I have never done this with "under 100Hz only" transducers, I will grant you that it may not work for subwoofers, unless they are run with (and properly aligned with) tops, which would be a very time consuming process that I'm sure would be outside the scope of the Shootout.
Post by: Nathan Short on August 02, 2007, 12:07:25 AM
| Ivan Beaver wrote on Wed, 01 August 2007 16:36 |
Good luck with the shootout. PS Be sure sure to get ahold of a BIG amplifier, you might need it for some of the cabinets. |
May I suggest the Powersoft K10, I recently put one in at a nightclub install, and is now my sub amp of choice (makes a Lab Gruppen 6400 sound broken) Don't jump down my throat Lab Gruppen fans, I still love them. I am just setting a very familiar subjective benchmark.
So unless Powersoft wants some press and decides to let you gents get your hands on the elusive yet to be seen K20, please consider the Powersoft K10.
Post by: Ivan Beaver on August 02, 2007, 08:20:16 AM
I do not know of any manufacturer (there might be some) that uses the lowest point on the curve as the impedance number. So if you do that, then somehow you are saying that you are "better" than the rest of the industry and want to do things differently than currently accepted. That is very open to discussion.
SO the nubmer you choose is now a determination by who?
And to further complicate it, you now have to reajdust the sending level to change the output voltage. So now you have adjusted something. It is all of these little adjustments that start to be the "problem", and start to bring up question regarding how the data was collected.
What if you choose a different number in terms of the impedance than someone else does, then who is right?
I say put a constant voltage into all the loudspeakers and go from there.
I used to be in the other camp and was wanting to simply put 1 watt in(changing voltage with different impedance), but started to realize all of the issues this brings up and am now in the camp of 2.83V and figure out the wattage that was applied from there. After all the wattage applied is different for all points on the curve and is only valid for one (and equal points of impedance).
WIth the TEF you can change the scales with post processing to account for different wattages/voltages so you can do a comparisom anyway you want. That is what Tom did after the NY shootout, but people were generally not interested ins seeing that, partly because they did not trust him, but I will tell you, Tom is one of the most anal people in this industry regarding real specs, and what he does can be trusted totally. He was not trying to play any games, but just rather present data in a way that would be easier for some to understand.
I would rather trust data that simply had scales moved up or down by a certain amount of db, much sooner than changing levels between measurements and those levels would be based upon a "determination" by someone, that could be easily be a different number as judged by someone else.
THAT is your big variable
Regarding who is doing the measuring (they are not hiding behind a curtain(are they?), one hting to consider is qualifications.
Is it better to have someone who has no relation to a manufacturer and has little experience in doing all of these types of measurements or someone who does this all the time and is aware of all the issues/problems that arrise and can head them off ahead of time and ensure accurate data?
If some people don't trust others to do measurements with someone looking over their shoulder. then I think they personally have a problem.
I would rather have a qualified person who does this for a living, anyday over someone who just does this on the side or part time or as a "hobby". This is not saying anything about who has been making your measurements-I don't know who that is, but rather about the attitude of people regarding who is doing the measurements.
The ONLY agenda of the measurement person should be to collect accurate data in a way that is industry accepted so that people can make their own determinations about the suitability of a product for a particular project. PERIOD. If they do anything to make one product look better or worse, they need to be exposed as a fraud.
The only way to ensure accurate/compariable data is to measure all of it the SAME way. Then people can post process it anyway they want-either mentally or with a program to determine what is what. IF you start changing drive levels, then it really gets hard to figure out what is what.
Post by: Mark Coward on August 02, 2007, 10:02:33 AM
http://www.jtrspeakers.com/2007_shootout.html
| Quote: |
Many of the speakers did not leave unscathed as three out of the five subwoofers prior to the Growlers had fallen victim to the PowerSoft K10 amplifier’s 10,000 watts. One channel of the amplifier when hooked up to each of the two Growlers is capable of 4000 watts. |
This is a little misleading according to the Powersoft and JTR specs, the Growlers are 8 ohm and the K10 is 2,000w RMS @ 8 ohm per channel. Both cabs on one side of the amp would be 4 ohm, and the amp is 4,000w RMS @ 4 ohm. The way I read the above, it sounds like it was one Growler per channel - but in either case, it would have been 2,000w max per cab.
I would really like to see some test results for power compression. What advantage is there in powering a 1,000w RMS driver with 2,000w RMS of amp, if power compression sets in at 500w?
Post by: Wayne Parham on August 02, 2007, 11:51:09 AM
| Ivan Beaver wrote on Thu, 02 August 2007 07:20 |
The impedance issue is where it really gets to be picky/touchy. If you do an impedance sweep, then what is the actual impedance? WHo is going to determine that? It is generally considered NOT to be the lowest point on a curve, but rather a "average" that relates to a standard "number". In just about every loudspeaker, there are more points that are much higher in impedance than those that are lower. |
The impedance sweep is quick and easy to do. I see no reason to omit it. At least then, people can see the exact impedance curve rather than depending on an advertised impedance value.
Many manufacturers have already expressed concern that without impedance being taken into consideration, their loudspeakers SPL appears to be lower than others.
We chose minimum impedance because it is a fixed tangible value. Average impedance is subject to interpretation. Minimum impedance works very well for setting power reference levels to compare SPL between speakers.
| Ivan Beaver wrote on Thu, 02 August 2007 07:20 |
I used to be in the other camp and was wanting to simply put 1 watt in(changing voltage with different impedance), but started to realize all of the issues this brings up and am now in the camp of 2.83V and figure out the wattage that was applied from there. After all the wattage applied is different for all points on the curve and is only valid for one (and equal points of impedance). |
I agree with you about measuring using a fixed voltage. In the technical sense, all measurements are made with a fixed voltage anyway. Amps aren't contant-power sources. But the point is, it's nice to gather data that reflects SPL at different reference levels, and many people are used to seeing power level references.
We measured using 28.3v, which from 10 meters away gives the same SPL as 2.83v at 1 meter. We also measured using 100 watts at 10 meters. This gave the same SPL as 1W/1M. After that, we doubled power and ran another sweep, continuing to do this until we reached maximum power. I kind of like that approach. You get both voltage reference charts and power reference charts.
| Ivan Beaver wrote on Thu, 02 August 2007 07:20 |
I do not know of any manufacturer (there might be some) that uses the lowest point on the curve as the impedance number. So if you do that, then somehow you are saying that you are "better" than the rest of the industry and want to do things differently than currently accepted. That is very open to discussion. |
Most manufacturers publish an advertised impedance, which is the closest multiple of 4 or 8 ohms. It's almost an arbitrary number.
| Ivan Beaver wrote on Thu, 02 August 2007 07:20 |
SO the nubmer you choose is now a determination by who? |
Exactly. That's why we chose minimum impedance. Minimum impedance isn't a value that requires interpretation or calculation.
Average impedance is always higher than minimum impedance. Using minimum impedance to calculate power, one sends a smaller voltage to the speaker than they would if they calculated using average impedance. The signal presented to the speaker then causes it to dissipate the expected power level at frequencies where impedance is minimum. At other frequencies, where impedance is higher, power dissipation is lower. So the measurement reflects a conservative SPL. It is, however, uniformly done across all speakers without interpretation.
The only way to accurately find average impedance it to take the measured impedance chart and find the area under the curve. But even this is subject to interpretation because you have to choose the frequency range to use. If you use DC to 100Hz, average impedance will be lower than if you choose 20Hz to 20kHz. At lower frequencies, reactive impedance from voice coil inductance isn't significant but at high frequencies, it dominates. So no matter what you do, average impedance is an interpretation.
Sure, you can say the range chosen should be the intended bandwidth of the device. But even that gives a little "wiggle room" because the band chosen for determining impedance can be shifted down, say from 30Hz-150Hz to DC-150Hz. This would give a lower average impedance, even if precisely calculated using the area under the curve. A small horn would be used over a different frequency range than a larger horn, so do you set a fixed band to calculate average impedance? Or do you let someone pick it? This leaves room for interpretation, which gives some ambiguity. It lets the person driving make choices that can offset the results, even if average impedance is precisely calculated.
That's why I suggest minimum impedance be used. If someone else has a suggestion for a method that can be accurately and uniformly applied, I'd love to hear it.
| Ivan Beaver wrote on Thu, 02 August 2007 07:20 |
And to further complicate it, you now have to reajdust the sending level to change the output voltage. So now you have adjusted something. It is all of these little adjustments that start to be the "problem", and start to bring up question regarding how the data was collected. |
To measure SPL at a fixed power level across various loads, you have to adjust voltage to account for impedance, that's right. But if you don't, then you have to massage the data to come up with the same thing. I think it is much better to have the exhibitor right there, watching the dial and seeing the voltage level set for his speaker before the test is run. He is then comfortable that his speaker has received the signal appropriate for the power tested for. Then when he sees the charts published, he can be comfortable that his speaker got a fair test.
| Ivan Beaver wrote on Thu, 02 August 2007 07:20 |
WIth the TEF you can change the scales with post processing to account for different wattages/voltages so you can do a comparisom anyway you want. That is what Tom did after the NY shootout, but people were generally not interested ins seeing that, partly because they did not trust him, but I will tell you, Tom is one of the most anal people in this industry regarding real specs, and what he does can be trusted totally. He was not trying to play any games, but just rather present data in a way that would be easier for some to understand. |
I don't think we should post-process because of the trust factor.
To adjust a response chart to account for impedance differences, you still have to calculate using an impedance figure. This figure must be interpreted at some point, be it minimum impedance or average impedance. Then the data has to be massaged to account for the difference. I personally would prefer that the impedance be measured rather than using advertised impedance or some other arbitrary figure to calculate an offset and then later massage the data.
I would welcome looking at other approaches to calculate power, but I don't think we should avoid power-reference measurements, choosing to make only voltage-reference measurements instead. I think we should do both.
| Ivan Beaver wrote on Thu, 02 August 2007 07:20 |
Is it better to have someone who has no relation to a manufacturer and has little experience in doing all of these types of measurements or someone who does this all the time and is aware of all the issues/problems that arrise and can head them off ahead of time and ensure accurate data? |
Naturally, it would be best if we had a qualified, independent and unaffiliated third-party. If that's not possible, we should self-police. But if we are going to self-police, we must be extra careful to make everyone comfortable.
| Ivan Beaver wrote on Thu, 02 August 2007 07:20 |
If some people don't trust others to do measurements with someone looking over their shoulder. then I think they personally have a problem. |
Absolutely. The measurement process and data should be open for inspection.
That's how we did it the past two years. I did the test plan and measurements in 2005, and everyone watched. When I set the voltage levels for the fixed-power measurements, I showed the exhibitor being measured the impedance chart, picked the minimum impedance, calculated voltage required to set power and showed the exhibitor that. Then turned the LMS oscillator on and set voltage, showing the exhibitor the meter. Everyone watched, the whole thing was open and I think everyone felt comfortable with the process.
David Lee did the measurements in 2006 and he basically did the same thing, but with a different system (Praxis) which had a different setup.
I am definitely open to suggestions and don't think I should be the final decision-maker, just like I don't think you or Mark or Tom should be. I think everyone would be better served with a concensus. So I definitely appreciate your input.
I think we agree in most things, but there are a few I think we might still need to hash through. Fixed-power measurements and impedance determination are two of them. Please look through my comments above and tell me what you think.
Post by: Ivan Beaver on August 02, 2007, 01:15:03 PM
I have NO problem with measuring impedance-assuming that the noise level aroudn the cabinets is quite-that will affect the impedance reading-sometimes quite a bit. But it is what you are trying to do with that data that I have a problem with.
The way you want to do it (using the minimum impedance) is out of industry standards, the ONLY thing you could even hope to compare would be between boxes measure at your shootout. Other boxes measured in different ways have no corrilation to your results-except maybe actual freq response, but with no absolute value assigned regarding sensitivity, becuase of the drive level you have choosen.
What if a particular box has one little spot that it is a good bit lower than the rest of the box-jsut for argument sake. You choose that value as the impedance and figure the voltage from that. But that is only a very small area of the freq response and not representative of the overall impedance of the cabinet. So therefore you have crippled that box in it's sensitivity.
Yes I totally agree that the rated impedances are just arbritrary numbers, but at least there is some coorilation to the actual impedance graph, but you have to have some standards. Just ask how people feel about a 6 ohm loudspeaker and they will usually ask what is wrong with it so that it doesn't have a "standard" value. It is usually so ocnfusing for them to think outside of their little boxes of 4-8 16 ohms.
Yes as a general rule lower impedance boxes have the "power" advantage, but that is easy enough figured out after the measurement by adding or subtracting a couple of dB.
Your way, you have no standard at all-every box will probably be driven with a different voltage-so trying to make any real comparisoms is going to be quite difficult. Lets see- box A was driven with 1.2dB higher voltage based on it's higher impedance and box C is driven with .6dB less because of it's lower impedance-so which box has the highest sensitivity?
And add to that the real need to do all the back calculating- Wayne says the boxes lowest impedance is 6.8 ohms, but over most of the freq range it is around 8.4 ohms. So therefore if I want to figure out what the rest of the world would have done is now I figure out what the drive voltage difference between the different impedances (or using the manufacturers rating of 8 ohms) actually is and then convert that to dB and add that to the measurements taken and now I have a cure that would respond to 2.83V drive.
That seems like a lot more extra work to me.
What I really wonder is why are you doing it this way, when the rest of the world is not. Are you really getting "better" data? Why not use industry standards. Anyway you look at it, you are going to have to convert something to something else to get some particular data that you are looking for, so keep it standard. 2.83V.
The real problem is that most of the people in our industry have no idea what we are even talking about and they just want a single number to give them all the answers, and it can't be done. So why try a new and different way to get the data?
I just wonder how many other people (especially manufacturers)feel that using the lowest point on an imedance curve is the proper way to figure out the drive voltage to arrive at the sensitivity? Yes it is A way, but I don't think it is the best or easiest way to understand what is really going on. Nobody (to my knowledge) at the NY shootout had a problem with the way Mark (and myself) were going about doing it.
Heck, most of the industry can't even agree on where the -3dB point is on a response graph. Just go look at their measured responses and the printed numbers on the specs and you will see that many manufacutrers claim a -3dB point (freq wise) that is really 9dB down from the rated sensitivity number. Where did that come from-I know exactly where it comes from-but that is a different rant.
If you DO NOT tie your sensitivity number to the -3dB FROM THAT NUMBER, the specs are pretty much worthless-but don't tell that to the buying public who believe everything they read!
Post by: Ivan Beaver on August 02, 2007, 01:20:13 PM
See this for some more info.
http://srforums.prosoundweb.com/index.php/m/231622/6883/#msg _231622
Post by: Tom Danley on August 02, 2007, 01:49:11 PM
Well Wayne, insinuation’s eh?
Ok so after quite some time had passed, the NY shoot out long over, I got a copy of the raw Data from the shootout, printed (raw) images of the curves and produced impedance compensated curves with a detailed explanation.
After the LAB didn’t put it up, we put them and the raw data on our web site.
Well (thinking of Steve Martin) EXCUUUUSE ME.
If you were more familiar with the TEF or how it worked, what it did, maybe you wouldn’t feel like that was cheating. Maybe your right, continuing on with no information would be better in your case, or curves like yours last year where you have to figure out what it is and re-plot it on a normal scale.
With the raw TEF data provided too, where exactly do you see a place to fudge anything anyway?
Regarding “who measures”;
For what its worth too, the only people your likely to find that really know how to do this stuff (like be proficient on a TEF machine), know how exactly because its been there job for some time and are usually associated with a company.
For example Ivan has probably set up and aligned more than a thousand auditoriums and stages with a TEF.
If a person from a participating speaker company isn’t acceptable to you or even a friend of a friend of one, you could obviously hire someone “un-involved” from the LAB.
You are the only person I can think of that has suggested that I fudge measurements too and insinuate that again here.
If you understood the big picture, with you again inferring that, you would also understand why I probably won’t recommend we send any speakers or equipment to your event.
I will leave you with some free advice, look at it as someone trying to trick you if you wish.
Use a TEF machine, for measuring a loudspeaker, like you are doing, like I do, it is I think the best tool available.
Heck, most (I won’t say all because I have not tried all of them) of the popular measurements systems don’t actually measure acoustic phase (while they do have a plot for it).
The erroneous phase graph has lead an entire movement of “fixing phase with all pass filters” based on bad (fictional) curves.
The TEF on the other hand passes the reality test I devised for phase.
Cheers,
Tom
Post by: Wayne Parham on August 02, 2007, 02:43:56 PM
Good dialog, Ivan, thanks. Let's continue to look at this.
| Ivan Beaver wrote on Thu, 02 August 2007 12:15 |
The way you want to do it (using the minimum impedance) is out of industry standards, the ONLY thing you could even hope to compare would be between boxes measure at your shootout. Other boxes measured in different ways have no corrilation to your results-except maybe actual freq response, but with no absolute value assigned regarding sensitivity, becuase of the drive level you have choosen. ... Yes I totally agree that the rated impedances are just arbritrary numbers, but at least there is some coorilation to the actual impedance graph, but you have to have some standards. Just ask how people feel about a 6 ohm loudspeaker and they will usually ask what is wrong with it so that it doesn't have a "standard" value. It is usually so ocnfusing for them to think outside of their little boxes of 4-8 16 ohms. |
You have suggested that there is a "standard" for published advertised impedance. I do not believe there is one. Advertised impedance appears to be an arbitrary number to me.
Minimum impedance, on the other hand is not arbitrary. Minimum impedance is easy to measure, definite and useful for making these kinds of comparisons.
Let's look at some actual impedance charts, shall we? Then we can run the numbers and see what we come up with.
This is the impedance chart of a Fitzmaurice Tuba 36. Looks to me like Zmin is 9Ω. From the forumula E = √PZ, we find the drive voltage required to dissipate 100 watts in a 9Ω load is 30 volts.
What would you say average impedance is? Should it be 8Ω, because that's the closest multiple of 8? Should it be 12Ω, since that's the next higher multiple of 4? Or should it be closer to 10Ω, since averaging the area under the curve up to 150Hz puts it closer to that?
Let's run the numbers and see what each of the drive voltages would work out to:
28.3v into 8Ω dissipates 100 watts
30.0v into 9Ω dissipates 100 watts
31.6v into 10Ω dissipates 100 watts
34.6v into 12Ω dissipates 100 watts
Now let's calculate the difference between each of these in decibels:
The 28.3v (8Ω) level is 0.94x the 30.0v level, which is -0.25dB.
The 31.6v (10Ω) level is 1.05x the 30.0v level, which is +0.23dB.
The 34.6v (12Ω) level is 1.15x the 30.0v level, which is +0.62dB.
We're only talking about a half decibel max difference between Zmin and any sort of realistic average impedance. You actually could eye-ball an average value and be pretty close, like probably less than +/-0.25dB. But the minimum impedance method uses a tangible number that nobody has to argue about. It's what you see on the chart.
Honestly, Ivan, I think we could go with fixed voltage measurements and calculate impedance offsets, just like you've described. I would be comfortable with that, and might do it myself if I were viewing my own data.
But what we're talking about here is confidence. This is an event where a lot of exhibitors will be bringing their best products to be compared with others. I think they would be more comfortable seeing what steps were taken to determine their SPL charts, right there in front of them. They see the impedance chart. They see the power formula run. They see the voltage set on the amplifier. And they then see the SPL chart made during the sweep, and that's what they see published later on the web. No surprises.
Post by: Ivan Beaver on August 02, 2007, 03:53:47 PM
What I have seen by looking at MANY manufacturers specs (and trust me I look at a lot) is when stating the sensitivity many say 2.83V 1M. Yes there are those that still say 1W but more and more they are saying 2.83V-impedance be damed
.There are some people that do say 1W/2.0V 1M for a 4 ohmn cabinet-so they are sticking with that spec type and that is fine-they are telling you exactly what is going on.
The assumption by the general public is that this is 1W, so it works in favor of the lower impedance cabinets, but there is a saying "buyer beware". They are not suggesting anything or saying anything false, but if the buyer misinterpets it or does not read the rest of the data sheet where it ways 4 ohms, then that is an issue that is up to them.
Most people are not concerned with how loud a cabinet is with a particular wattage input. There are two concerns. 1: How loud is this cabinet when I hook it up to my so and so amp. 2: How many of these cabinets can I hook up to my so and so amp without damage?
When you really dig into the wattage issue it raises questions.
Let's look at your example of Bills cabinet. Where is the highest impedance point? Right where a lot of kicks are tuned to-between 60-70 Hz. PLEASE LABSTERS let's not turn this into a where is your kick drum tuned to thread
. This is just an example. So at that freq (which is where many would require the greatest amount of output (talking rock type stuff here) the amp is seeing a very high impedance and actually putting out very little power. Therefore if the kick is your primary source of volume in the sub, then you might could actually hook up more than would be normally suggested as safe-BUT you did not read me saying that .I am siding with the rest of the industry @ 2.83V.
It is very much like back in the late 80's and the pin 2 pin 3 issue and what was standard.
It is hard for a manufacturer to change to the "new" standard when they have been doing so fo so long in a particular way. It would confuse the general public. Look at JBL and red negative for example. They are different than the rest of the world (as far As I know), but still do it, and with good reason. Most people understand this-but many still learn every day-It was quite eye opening when one of my competitors told me this oh so many years ago-I didn't belive him untill I took a battery to one myself.
I would love to here how others feel about what the input should be-a constant voltage or a voltage derived from the lowest impedance on the curve and not the manufacturers rating.
What would they like to see-not only at a shootout, but on spec sheets in general?
Post by: Tim McCulloch on August 02, 2007, 04:06:22 PM
| Wayne Parham wrote on Wed, 01 August 2007 19:35 |
You and Mark Seaton are both personal friends and business associates with Tom Danley. The fact that the data was gathered, organized, processed and published by you and Tom made some people pretty uncomfortable. They told me so. Again, please don't take that wrong. I saw what you guys did and I could tell you were trying to be fair. But please understand that it's the same thing as if Danley had to trust measurements I made, processed and published. He has been pretty vocal that he would be uncomfortable with that. I understand, and I don't expect him to be forced to accept a situation that makes him uncomfortable either. We'll need to work in a spirit of understanding and cooperation to find and agree on methods that everyone is comfortable with. |
The data from the NYC Sub shootout wasn't altered in any material way I could determine. I was there, I watched and listened to the measurement process. While I'm not a TEF expert, I've measured a few speakers for acoustic performance, and have comprehension of what takes place. Every speaker received identical treatment (as best we were able). The results were obviously influenced by the small and severely reflective space, but what was released publically jived with my memory of what I saw on-screen in NYC.
The "Monday morning quarterbacking" after the results were released left a bad taste, and made the agendas of several individuals readily apparent. I suspect that some of those folks would have been unhappy regardless of who's fingers were pushing the buttons. Oh well, water under the bridge...
Good luck in October, if I'm not working I'll try to be there.
Tim Mc
Post by: John Roberts {JR} on August 02, 2007, 04:09:30 PM
Since these impedances are not flat lines or simple to evaluate I would be interested in minimums within the expected passband. A dip at 20kHz in a woof is not much concern. In full range cabinets another story.
So SPL for a given voltage with an asterisk for impedance which is only important when unusual. I prefer to see plots but I am not the typical customer for these shoot outs. A minimum will tell the typical customer what (s)he needs to know.
Post by: Wayne Parham on August 02, 2007, 09:26:28 PM
| Ivan Beaver wrote on Thu, 02 August 2007 14:53 |
What I have seen by looking at MANY manufacturers specs (and trust me I look at a lot) is when stating the sensitivity many say 2.83V 1M. |
We're measuring 2.83v/M, always have and always will. Actually, we measure using 28.3v at 10 meters, which is the same SPL, as you know. So you can use that figure and disregard the others, if you wish.
Post by: Wayne Parham on August 02, 2007, 09:54:52 PM
| Tim McCulloch wrote on Thu, 02 August 2007 15:06 |
The data from the NYC Sub shootout wasn't altered in any material way I could determine. I was there, I watched and listened to the measurement process. While I'm not a TEF expert, I've measured a few speakers for acoustic performance, and have comprehension of what takes place. Every speaker received identical treatment (as best we were able). The results were obviously influenced by the small and severely reflective space, but what was released publically jived with my memory of what I saw on-screen in NYC. |
I don't think anyone said the NYC data was altered. Some were just uncomfortable with how it was handled. So what we've learned from that is to be careful with what we do and how we do it.
Post by: John Roberts {JR} on August 03, 2007, 12:24:28 AM
| Wayne Parham wrote on Thu, 02 August 2007 20:54 |
I don't think anyone said the NYC data was altered. Some were just uncomfortable with how it was handled. So what we've learned from that is to be careful with what we do and how we do it. |
Any names or specifics?
I wasn't uncomfortable, but I don't have an axe to grind.
JR
Post by: Ivan Beaver on August 03, 2007, 07:39:41 AM
| Wayne Parham wrote on Thu, 02 August 2007 21:26 |
We're measuring 2.83v/M, always have and always will. Actually, we measure using 28.3v at 10 meters, which is the same SPL, as you know. So you can use that figure and disregard the others, if you wish. |
Then why have you been insisting on measuring the impedance and then figuring out what voltage it would take to get 1 watt based on that reading so much? That is no longer 28.28V.
I am so confused now.
Post by: Ivan Beaver on August 03, 2007, 07:44:34 AM
Yet YOU are are manufacturer and want to be in total control of what happens.
David Lee is also a manufacturer and yet he did the measurements last year.
Oh I get it, you only want CERTAIN people (that you appoint) to be in control of the data, now I understand
I guess it is part of who the "IN" crowd is.
Post by: Wayne Parham on August 03, 2007, 10:39:49 AM
| Ivan Beaver wrote on Fri, 03 August 2007 06:39 |
Then why have you been insisting on measuring the impedance and then figuring out what voltage it would take to get 1 watt based on that reading so much? That is no longer 28.28V. I am so confused now. |
Refer back at the test plan:
We measure at 28.3v, 100 watts, 200 watts, 400 watts, and so on. You can pay attention only to the 28.3v charts if you wish.
Post by: Vince Byrne on August 03, 2007, 10:51:27 AM
Although I have no idea why he would want to step up for a beating in the House of Pain ...
| Ivan Beaver wrote on Fri, 03 August 2007 06:44 |
Let me try to understand this. You do not want somone associated with a manufacturer to measure the data or deal with it. Yet YOU are are manufacturer and want to be in total control of what happens. |
Don't be confusing the issue with facts now ...
Peace,
Vince
Post by: Wayne Parham on August 03, 2007, 10:54:49 AM
| Pascal Pincosy wrote on Tue, 31 July 2007 18:03 |
What's the plan for taking measurements this year? I'd like to see someone who is not affiliated with a manufacturer at the controls this year. |
Me too, absolutely. ProSoundWeb's Sara Elliott said that might be arranged. She has to talk with Mark Herman first though.
We had hoped to get one of the forum regulars that was unaffiliated with any manufacturer to perform the measurements at past Prosound Shootouts in 2005 and 2006. When that couldn't be arranged, all the exhibitors discussed the problem of who would do it and we agreed to self-police. It really wasn't a problem, but it is more objective if an outside party runs the show. It's also allows the exhibitors to focus on setup rather than to divide their time between that and taking measurements.
| John Roberts {JR} wrote on Tue, 31 July 2007 19:34 |
I like to give them the benefit of the doubt, but with two (or more) we could A) know what and how to measure, and B) keep each other honest. I suspect if we came up with some pre-discussion of what is to be measured, and saved raw data, we should be able to parse to our own satisfaction, later. Trust but verify... JR |
That's how we did it the past two years. I did the test plan and measurements in 2005, and everyone watched. When I set the voltage levels for the fixed-power measurements, I showed the exhibitor being measured the impedance chart, picked the minimum impedance, calculated voltage required to set power and showed the exhibitor that. Then turned the LMS oscillator on and set voltage, showing the exhibitor the meter. Everyone watched, the whole thing was open and I think everyone felt comfortable with the process.
David Lee did the measurements in 2006 and he basically did the same thing, but with a different system (Praxis) which had a different setup.
In both prior events, the measurement system and datasets gathered were open and available to everyone. David and I in particular double-checked each other's work. We will do the same thing this year, and welcome any and all of the exhibitors to provide input and become involved.
I am definitely open to suggestions and don't think I should be the final decision-maker, just like I don't think Tom or Mark or Ivan should be. I think everyone would be better served with a concensus. So I definitely appreciate everyone's input.
Post by: Ivan Beaver on August 03, 2007, 11:13:43 AM
That's how we did it the past two years. I did the test plan and measurements in 2005, and everyone watched. When I set the voltage levels for the fixed-power measurements, I showed the exhibitor being measured the impedance chart, picked the minimum impedance, calculated voltage required to set power and showed the exhibitor that. Then turned the LMS oscillator on and set voltage, showing the exhibitor the meter.
To me it looks like you are adjusting the voltage based on the impedance and not using the smae voltage for all loudspeakers.
Post by: Wayne Parham on August 03, 2007, 11:53:08 AM
| Ivan Beaver wrote on Fri, 03 August 2007 10:13 |
I guess where the confusion came from was this statement from you That's how we did it the past two years. I did the test plan and measurements in 2005, and everyone watched. When I set the voltage levels for the fixed-power measurements, I showed the exhibitor being measured the impedance chart, picked the minimum impedance, calculated voltage required to set power and showed the exhibitor that. Then turned the LMS oscillator on and set voltage, showing the exhibitor the meter. To me it looks like you are adjusting the voltage based on the impedance and not using the smae voltage for all loudspeakers. |
We do both. We measure first at 28.3v. Then we measure at 100 watts and higher power levels, doubling each time until we reach max power.
Post by: Ivan Beaver on August 04, 2007, 01:38:25 PM
Your order is wrong! You are simply generating an impulse response from the amplitude measurement. The problem is that if you don't actually MEASURE the impulse response, you have no idea where to set the correct delay in the measurement system. This will result you different measurements-as you have obviously found out.
The only way to generate an impulse response (without actually measuring it-which I do not see in your plan) is with an ACCURATE freq response. If your delay is not set right, the amplitude will be in error, so therefore the transformed impulse resonse will also be wrong.
Try measuring the impulse response FIRST (to set your delay) and then the amplitude response. That way you won't have to make so many measurements.
That will give you much more time for listening-which appears to be low on your list of importance. Lots of time for invalid measurements is much higher
.Post by: Wayne Parham on August 04, 2007, 03:38:43 PM
| Ivan Beaver wrote on Sat, 04 August 2007 12:38 |
I was just looking over your test plan and realized why it takes you mulitple measurements in order to get 3 that agree so that you have "good data". Your order is wrong! You are simply generating an impulse response from the amplitude measurement. The problem is that if you don't actually MEASURE the impulse response, you have no idea where to set the correct delay in the measurement system. |
That's not true. Have you never worked with LMS?
Look over the LMS documentation and you'll see that our test plan is exactly how they say the system should be used.
We don't need three samples using LMS. It gathers the same data on every sweep. Come on out and see.
Post by: Ivan Beaver on August 04, 2007, 03:47:39 PM
Without this information, all bets are off on the accuracy of the measurement. How does the window know when to open or close?
Post by: Wayne Parham on August 04, 2007, 04:09:36 PM
| Ivan Beaver wrote on Sat, 04 August 2007 14:47 |
How does the window know when to open or close? |
Being an outdoor measurement, there is no need for gating.
What you are describing applies to pseudo-anechoic measurements, where samples are gathered only for a brief period. It is an attempt to gate out reflections of measurements made indoors, by sampling only sounds present prior to the first reflection. You have to know how far your boundaries are to setup a pseudo-anechoic measurement. It's a way to measure indoors, but it only works if the boundaries are further away than a wavelength of the lowest frequency you want to measure.
Gating isn't needed outdoors, in a truly anechoic environment.
Post by: Luke Sheridan on August 04, 2007, 05:16:07 PM
Post by: Ivan Beaver on August 04, 2007, 05:53:00 PM
Everybody else seems to have issues with those sorts of things. Now if you were measuring at loud levels at the mic position, you can overcome this somewhat, but when measuring in the 70-80dB range (as indicated on your response curves from last year) it would not take much to contaminate the measurement-heck even a car system a good distance away would cause a problem.
Since you don't have any time information (or way to window), you might as well use an RTA
Post by: Wayne Parham on August 04, 2007, 10:39:21 PM
| Ivan Beaver wrote on Sat, 04 August 2007 16:53 |
Since you don't have any time information (or way to window), you might as well use an RTA |
LMS is capable of gated measurements. Sometimes, I use gating when I want to measure indoors in the winter or something. If I want to measure a midrange, tweeter or something at higher frequencies, it's perfect.
But it's tough to get decent bass measurements indoors, so that's why we chose a large open outdoor space for this event. Since we're performing measurements outdoors, gating isn't used.
Post by: Tom Danley on August 05, 2007, 09:57:22 AM
You right, without time discrimination, one could use an RTA.
One difference though is that an RTA does not have a plot for acoustic phase, where LMS has a “pretend” one.
LMS is one of the many popular measurement approaches, which has a plot for “acoustic phase” but doesn’t measure the actual acoustic phase and is wrong at least part of the time.
On the other hand, if he were in the middle of a big open flat reflection free space, had his level at least 20dB over the biggest peaks in the noise floor, then he could still get realistic amplitude response measurements.
On the other other hand, that criteria is difficult to maintain if your measuring down the roll off slopes of the speaker.
Here too (in addition to measuring actual acoustic phase), the TEF / TDS process provides vastly better noise immunity too, oh well.
Best,
Tom
Post by: Ivan Beaver on August 05, 2007, 10:27:08 AM
I was being sarcastic about the RTA.
With his measurement levels, the noise floor in the bass regions would need to be in the 50 to maybe 60dB range. Pretty hard to do. That is why I suggested measuring louder.
But it gets even more confusing. He said that they "ALWAY HAVE ALWAYS WILL" use 28.3V. But the actual measurements displayed show 2.83V actual sensitivities @10M.
Maybe there is some "adjustment" going on here, I don't know why, and was that "adjustment" actually calibrated with a MIC calibrator or not a preset. It just opens up all sorts of possibilities about the error of the data.
It might be comparible to the cabinets at the shootout, but what about to the rest of the world?
Still wondering-----------
Post by: Wayne Parham on August 05, 2007, 10:30:31 AM
| Tom Danley wrote on Sun, 05 August 2007 08:57 |
On the other hand, if he were in the middle of a big open flat reflection free space, had his level at least 20dB over the biggest peaks in the noise floor, then he could still get realistic amplitude response measurements. |
That's exactly what we do. The test environment is an open space, free of reflections. As shown in the test plan, we measure the ambient noise level first. It's one of the published datasets.
By the way, since Ivan brought up gating, how did you guys setup for the NYC event in January? How far away were the walls and how did you set gating to make your measurements pseudo-anechoic? It looked to me like the room was much too small to gate out reflections at subwoofer frequencies. Please explain your approach, and how TEF was able to correct for the room.
Post by: Tom Danley on August 05, 2007, 01:06:23 PM
You said;
“By the way, since Ivan brought up gating, how did you guys setup for the NYC event in January? How far away were the walls and how did you set gating to make your measurements pseudo-anechoic? It looked to me like the room was much too small to gate out reflections at subwoofer frequencies. Please explain your approach, and how TEF was able to correct for the room.”
You have several misconceptions chained together in one paragraph.
First, I wasn’t at the NYC shootout, I had nothing to do with its planning, set up, organization other than knowing Mark and Ivan who ended up running the TEF.
We did send a couple boxes to the event, so at least in that way I was involved or at least represented. Your issue with my involvement was that after some good while had gone by and no one had the time to do it, I post processed and scanned the measurements (the ones you were concerned about) and made them and the original data available on our web site after PSW hadn’t posted them.
Second, if you were more familiar with acoustic measurements, or, had read the explanation I posted with the data, you wouldn’t have asked, you can’t gate out reflections like that, even with a TEF machine.
When we or I measure subwoofers, it is outdoors at 10 meters.
On the other hand, sometimes all you have is an indoor space to deal with so they did as good as they could.
If you have a problem with what they did, where and how they did it, you might look up the folks who arranged it and address them instead.
Tom
PS you say “As shown in the test plan, we measure the ambient noise level first”
This is fine as long as the measurement on the speaker is at the same time as the measure of the noise floor. Most of the time though the noise floor is a variable, not a fixed quantity so a fixed sampling is the crudest possible view, but, still better than none at all.
Odds are, at the low frequency end of the scale, you will still see significant changes from measure to measure due to insufficient noise immunity.
On the other hand if every sweep is the same at the lf end, then no.
Post by: Ivan Beaver on August 05, 2007, 02:39:42 PM
Note I thought the event went pretty well and a good time was had by all, but we DID NOT end up with any real usefull measurements.
When Mark got there, he and I started discussing about how best to go about this. Where to place the subs, where to place the mic etc. Taking into account slapback reflections, rear reflections wall etc.
I think we ended up with the best possible locations In that room. No, nowhere near great, but all that we could do in the space provided. The small space was great for fellowship, but lousy for sub measurements.
Anyway, when you go low in freq, you have to open the time window up wider and wider. This lets more and more of "the room" into the measurement.
As I have said in the the results section of the NY shootout, when you lay the curves on top of each other, you will see that the room was a very dominating factor involved. You will see the same dips and peaks across just about all of the loudspeakers there. The better/flatter loudspeakers were simply acting as pistons in the room and the room coming back into the mic was cauing most of the responses measured. I simply do not believe that with the large variety and different types of subs there, they all had some very common relationships in response.
The only thing that the measurements showed that were of any real vaue was that some cabinets had a lower low freq extension than others. But these are not totally accurate, because of the room issues. The other thing is shows is the basic sensitivity difference of the cabinets with the same voltage applied. We don't know what it was, because the only volt meters that were available had a fairly large difference between them.
The one thing that came out of the NY shootout was that you can't measure subs indoors! At least ending up with any data that could be used to compare to other manufacturers standard measurements. It is for that reason that I feel you need to stick to standard measurements-because you actually have a place where that can happen. Those are not easy to come by. That way you could take your measurements and compare them to other manufacturers that actually publish the response data (a lot don't want to-just look at our number and believe it is "true"
)Of course I knew this going in, but was hoping for a larger room. A good time was had by all, and that was important-in my eyes.
The one thing that didn't show up on any measurements was how the different subs "sounded". This became apparent on the 2nd day of listening. Some were punchier than others, some sounded like they were "doubling over inside the cabinet", Others were tight and others were loose. All could shake the room but the ones that could make the floor feel like it was making waves in the floor could be counted on one hand, with most of the fingers missing.
I can't say for sure, but I feel most people in attendance liked the second day better. There just seemed to be more interaction between people there and more "fun" overall.
Post by: Iain_Macdonald on August 05, 2007, 04:13:37 PM
This all looks like fun - if you like migraines, and the personal attacks!!! At some point we need to do this type of event in Europe.
Trying to get someone who is really independent to do the measurements would be the best way of proceeding. But how? Having been on both sides of the fence (customer/manufacturer), I know that in the past, some manufacturers would try anything to get an advantage. At the NY event I recall a couple of companies coming up with higher rated drivers a short time before the event. OK they are now in the "catalogue", but that seems marginally unfair on other manufacturers who brought along their stock product. Maybe a 'specials' category would be appropriate.
Whilst TEF is a good measurement system. It lacks the ability of other systems to do certain tests which are required. LMS is also lacking. Praxis, which you have available, is much more suited to this type of event. Distortion testing is very important. So please don't be persuaded otherwise. Multi-tone testing will reveal some unpleasant aspects of deficient products. Like bad porting, horn irregularities, box panel modes, construction problems, and the like. Take a look at John Risch's website for an interesting paper on the selection of appropriate frequencies. I also favour the idea of using shaped tone bursts for power testing and distortion analysis. Again this is available in Praxis. Don Keele has an interesting paper on this type of test. People who argue against the multi-tone and burst tests, might just have something to hide! The NY tests that were published on BP's site did not include any decay response. Will that happen with your event?
The question about minimum impedance has always been a thorny question. But the AES addressed it in AES2-1984 (r2003) and other publications. They recommend using the minimum value measured over it's operating bandwidth. Personally I would like to see a complex statistical weighted 'average' over the operating range.
Best wishes.
Iain.
Post by: Ivan Beaver on August 05, 2007, 04:21:08 PM
Time is the biggest issue for the Tulsa shootout (as I see it).
Post by: John Roberts {JR} on August 05, 2007, 04:58:20 PM
| Ivan Beaver wrote on Sun, 05 August 2007 15:21 |
The biggest problem in any type of shootout, is what to measure, how to measure it/and present it in a form that other people will be able to use (the biggest issue in the NY shootout), in the amount of time alloted. If you have a decent number of cabinets, this can become quite exhausting (time and energy wise) to try and perform many tests on every cabinet. Time is the biggest issue for the Tulsa shootout (as I see it). |
While a little late, but not too late... The NY shoot around appears to have had room mode interactions. It seems to me that one or two MFRs curves (if actually accurate), might be useful to decode the reading in the room. Sort of working backwards to extract a room curve from the speaker readings.
If two or more such comparisons agreed about the disagreement, it might be useful to help interpret all the readings. I may be a little optimistic in my expectation that manufacturer's curves be accurate but why not until proved wrong.
JR
Post by: Ivan Beaver on August 05, 2007, 07:12:30 PM
If one were to spend the time (a lot of time would be involved here) and try to "deconvolve" the measurements against a know good one taken outdoors, then the ridicule and mistrust etc would be overwhelming.
When Tom tried to post the "normalized to 1Watt" using the manufacturers specs, he was meet with a large amount of resistance because he was one of the players in the shootout.
I think the place Wayne is doing it is pretty good (about as good as you are going to get anyway), I just have a few questions about how the measurements are being done. Little things mostly that can make a fairly good sized difference in the overall results. Or skew them anyway.
The possibility for some really good measurements is there. It just needs to be in a way that could be compared to "standards".
It is not about "cheating" or "trying to get an edge" or "falsifying specs". It is all about getting data that could be used by others in a reliable way. That is ALL that I am asking.
Post by: John Roberts {JR} on August 05, 2007, 07:37:58 PM
JR
Post by: Grant Rider on August 06, 2007, 12:40:33 AM
| Wayne Parham wrote on Sat, 04 August 2007 21:09 | ||
Being an outdoor measurement, there is no need for gating. What you are describing applies to pseudo-anechoic measurements, where samples are gathered only for a brief period. It is an attempt to gate out reflections of measurements made indoors, by sampling only sounds present prior to the first reflection. You have to know how far your boundaries are to setup a pseudo-anechoic measurement. It's a way to measure indoors, but it only works if the boundaries are further away than a wavelength of the lowest frequency you want to measure. Gating isn't needed outdoors, in a truly anechoic environment. |
| Ivan Beaver wrote on Sun, 05 August 2007 19:39 |
Note I thought the event went pretty well and a good time was had by all, but we DID NOT end up with any real usefull measurements. When Mark got there, he and I started discussing about how best to go about this. Where to place the subs, where to place the mic etc. Taking into account slapback reflections, rear reflections wall etc. I think we ended up with the best possible locations In that room. No, nowhere near great, but all that we could do in the space provided. The small space was great for fellowship, but lousy for sub measurements. Anyway, when you go low in freq, you have to open the time window up wider and wider. This lets more and more of "the room" into the measurement. As I have said in the the results section of the NY shootout, when you lay the curves on top of each other, you will see that the room was a very dominating factor involved. You will see the same dips and peaks across just about all of the loudspeakers there. The better/flatter loudspeakers were simply acting as pistons in the room and the room coming back into the mic was cauing most of the responses measured. I simply do not believe that with the large variety and different types of subs there, they all had some very common relationships in response. The only thing that the measurements showed that were of any real vaue was that some cabinets had a lower low freq extension than others. But these are not totally accurate, because of the room issues. The other thing is shows is the basic sensitivity difference of the cabinets with the same voltage applied. We don't know what it was, because the only volt meters that were available had a fairly large difference between them. The one thing that came out of the NY shootout was that you can't measure subs indoors! At least ending up with any data that could be used to compare to other manufacturers standard measurements. It is for that reason that I feel you need to stick to standard measurements-because you actually have a place where that can happen. Those are not easy to come by. That way you could take your measurements and compare them to other manufacturers that actually publish the response data (a lot don't want to-just look at our number and believe it is "true" ) |
I think now everybody agrees there is no way to measure a subwoofer inside a room unless it is very big. The room will always contaminate the results. Hopefully everybody that was at NYC can go to Tulsa to get accurate measurements.
Post by: Grant Rider on August 06, 2007, 01:19:00 AM
>> NYC sub shootout 2007, Part 1
>> NYC sub shootout 2007, Part 2
>> Tulsa sub shootout 2006
>> Tulsa sub shootout 2005
Post by: Grant Rider on August 06, 2007, 02:21:28 AM
| Iain Macdonald wrote on Sun, 05 August 2007 21:13 |
The question about minimum impedance has always been a thorny question. But the AES addressed it in AES2-1984 (r2003) and other publications. They recommend using the minimum value measured over it's operating bandwidth. |
That would seem to settle the matter of impedance.
Post by: Pascal Pincosy on August 11, 2007, 04:03:29 PM
| Ivan Beaver wrote on Sun, 05 August 2007 21:21 |
The biggest problem in any type of shootout, is what to measure, how to measure it/and present it in a form that other people will be able to use (the biggest issue in the NY shootout), in the amount of time alloted. If you have a decent number of cabinets, this can become quite exhausting (time and energy wise) to try and perform many tests on every cabinet. Time is the biggest issue for the Tulsa shootout (as I see it). |
I have a suggestion on how to speed up the overall flow of the testing at the shootout-
There are two major time-suckers: measurements of cabinets, and time-aligning the subs to the reference tops for the listening tests.
My suggestion is to have two separate measurement systems available. The first would be for taking the reference measurements for posting. The second (set up in a separate area) would be for manufacturers to use to align their subs to the tops. Day one would consist of taking measurements. While subs are getting swapped out and set up in the measurement space, other subs could be getting aligned by the manufacturers rep. Settings are saved, and then used the following day for the listening test. This would take a bit of coordination, but would save significant time overall.
In regards to having an independent (and hopefully unbiased) person taking measurements, I'd like to suggest an entrance fee for manufacturers that would help cover the costs of getting a measurement operators expenses covered in order to attend. Since the event is being sponsored by ProSoundWeb, I'd expect the overall expense to be mitigated. Accommodations would have to be made for subwoofers that are not being brought by the manufacturer, but by an individual. We certainly would all like to see how the little guys measure up against the big boys who are too scared to bring their cabinets to a shootout.
A shootout of this type is a big marketing boost for manufacturers. I see no reason why it wouldn't be of benefit to everyone that an independent measurement operator be present, both to ensure accurate results, but also to remove any questions of impropriety. Given the potential benefits (just look at how JTR's sales have benefitted from the NY Shootout,) I would think that dropping a small amount of cash for a measurement operator would be a boon to the companies involved.
Post by: Ivan Beaver on August 11, 2007, 05:43:32 PM
The problem with that is that now you have questions like "I need to hook up a 8.2 ohm with a 5.6 ohm and a 7.5 ohm loudspeaker-I am so confused as to what amp to use"
"Please help and make it simple". Math is so hard
And if you start to use that for 1W sensitivity numbers you end up with all different sorts of drive voltages.
I am of the camp of 2.83V regardless of impedance and let the customer look at the impedance curves and determine for themselves what impedance they think the box should be rated at-yes that is a bomb getting ready to explode
. Because that would actually require a little knowledge and thought process on the part of the consumer-which might require thinking and sometimes that hurts. "Just give me a number and I will blindly believe it-no matter what the spec sheet says".As in all things audio, there are many ways of looking at the exact same data and coming up with different opinions as to the spec. Impedance is just one of those. So you use the minimum, or an average or a standard number as long as the minimum is not a certain percentage (whatever that might be) below a standard value.
And since impedance is different at most all freq the load presented to the amplifier is constantly different,and what if the end users never hits those minimum freq points, then the load on the amp is less, and since music is constantly changing, the load is always changing also.
Sometimes you need to use a "nominal" number-as most all manufacturers do. That is why it is referred to as "nominal impedance".
This could be discussed to no end with nothing coming out of it, and just about all parties would be right, just having a different interpretation.
Post by: Wayne Parham on August 13, 2007, 11:29:54 AM
Impedance is always measured and posted, as is the 2.83v SPL chart. So you'll have both. You'll also have SPL at various power levels. As we saw earlier in the calculations of what to expect using minimum impedance verses some kind of average, it's very close, within a fraction of a decibel. So choose which ever dataset you're most comfortable with. The information gathered will be presented in a variety of ways.
David Lee will be bringing his LMS system and I'll have mine there as well. That way we can have both systems running to speed the process. One will setup for measurements while the other is running a sweep. We can get the most done that way.
Post by: Jeff Permanian on September 18, 2007, 05:07:34 PM
Set "Analyzer - Parameters" Frequency to 40Hz. Then click "Osc On" or press F10. Set the voltage level to 80% maximum power and leave running for 15 minutes.
Repeat steps 4 - 6 at high power levels, comparing results with the measurements made at the same power levels prior to heat soaking the driver."
Not very many speakers will survive sine wave at 80% max power.
Post by: Ivan Beaver on September 19, 2007, 08:29:20 AM
| Jeff Permanian wrote on Tue, 18 September 2007 17:07 |
"7. Heat soak the speaker. Set "Analyzer - Parameters" Frequency to 40Hz. Then click "Osc On" or press F10. Set the voltage level to 80% maximum power and leave running for 15 minutes. Repeat steps 4 - 6 at high power levels, comparing results with the measurements made at the same power levels prior to heat soaking the driver." Not very many speakers will survive sine wave at 80% max power. |
Yet another reason why I question his "test" procedures and results.
I really wonder how he determines the 80% power, when he is just applying a single freq sine wave at a given voltage. What he is forgetting is that what he calls a "power amplifier" is not that. It is a VOLTAGE amplifier. The end result of power, is an applied voltage ACROSS a given impedance. What if a loudspeaker has a peak in the impedance at 40Hz?
Then the actual power delivered to the loudspeaker is nowhere near what he "thinks" it is. So again the number are not comparible-IF that is what he is trying to do.
Remember the old Cerwin Vega Eathquake cabinets that had the reputation that you could plug them into a wall outlet? How do think this is possible? With an impedance peak of 60Hz of course, so that the ACTUAL power going to the driver was quite a bit less than you would think it would be (if it were 8 ohms at that freq).
Now if you have to do a lot of math crunching to figure this out, why they wasting so much time for such usless non real world tests?
Personally I think he needs to spend a lot less time trying to do tests that do not have any relivance, and a lot more time calibrating a system so that he has consistant results that could be used to compare to other measurements-not taken at his event.
But sadly the only thing that comes out of his event is a comparison to cabinets that were present that year. you can't even compare them to cabinets of the previous year (judging by the history), which makes it pretty much worthless.
Unless you just want to go to the race that night And I am not talking different measurement platforms, but just how different the "measurements" are from year to year of the same cabinet.
As was told to me in my first TEF class "What am I hear to do?" You can waste lots of time doing measurements that mean nothing, but getting good usable data is the most important. At least to me.
Post by: Wayne Parham on September 19, 2007, 11:00:56 AM
We probably won't do the heat-soak test, due to time constraints. It just takes too long. Pity, because it is an interesting and useful test. We'll do all the other tests, impedance, response and distortion at various drive levels.
The heat-soak test isn't a destructive test. It shows how much electro-mechanical parameter shift there is at high power levels. You use the maximum continuous RMS power level the loudspeaker can handle and back it off a little to be safe. Maximum continuous RMS power is a pretty common specification, most manufacturers publish it. Run at 80% of that level long enough to heat the motor, then perform tests on the speaker after it has been heat-soaked.
You might be surprised how differently speakers behave after they've been in use for a while. They act like the woofer has much higher Q. In fact, that's exactly what happens. You can see it in the response curve, which usually develops a peak at low frequency. Some speakers get very peaky down low, others not so much.
The heat-soak test is a useful test that shows how speakers behave in real-world use. Interesting power levels to examine are 80%, 50% and even 30%. Most speakers begin to shift much sooner than full power. This test helps us see how much a loudspeaker's characteristics shift at various power levels. You can see how robust a loudspeaker is with this test. Try it sometime.
Post by: Jeff Permanian on September 19, 2007, 03:15:00 PM
Has there been any other manufactures commit to providing subwoofers for the shootout? There is a new sub coming to market that the growler would love to gobble up.
Post by: Mark Hobbs on September 19, 2007, 03:29:03 PM
| Jeff Permanian wrote on Wed, 19 September 2007 14:15 |
Has there been any other manufactures commit to providing subwoofers for the shootout? There is a new sub coming to market that the growler would love to gobble up. |
What new sub would that be? Is it a Danley?
And Jeff, are your tops going to be there?
Post by: Wayne Parham on September 19, 2007, 04:16:17 PM
| Jeff Permanian wrote on Wed, 19 September 2007 14:15 |
Using band limited pink noise might be a more universal way to heat soak subwoofers because of the varying resistance between speakers at any given frequency causing inconsistent power consumption and heat saturation. |
You could do that, sure.
But while impedance varies with frequency for every loudspeaker, it does not vary with respect to a single frequency. Power consumption isn't inconsistent, rather, it is precisely known for any given frequency. We measure impedance before we measure anything else, so it is easy to set the applied voltage to cause a specific power level to be dissipated by the loudspeaker.
If you're talking about power, then you've necessarily taken impedance into account. Ohm's law is pretty basic stuff, and if you know impedance, you can easily find the proper voltage to cause a specific power to be dissipated.
If you think about it, if you really want an exact precise power level to be dissipated, using a fixed sine wave is a better source than pink noise would be. A pink noise source is a mix of random frequencies, so you would basically be measuring an average. I don't think that matters too much, and you could sure use it. You're really just trying to heat the speaker, and precision to the 0.0001 watt level isn't required.
Basically, I don't think it matters too much what signal you use to heat the core. What's more important is that you know how the speaker acts at sustained levels around full power, half power and maybe quarter power. That gives views of performance data at power levels more in line with how the speakers are actually used. It's just more information, and I'm sorry we probably won't have time to measure it.
| Jeff Permanian wrote on Wed, 19 September 2007 14:15 |
Has there been any other manufactures commit to providing subwoofers for the shootout? There is a new sub coming to market that the growler would love to gobble up. |
The people that have committed to attending so far are listed on the Prosound Shootout website. The only additions to that are Lance Klaurens said he wants to bring some subs, big-name boxes, I think. David Lee may also bring his JBL subs, just for comparison. I don't know, but I'll find out in the next week or so and post them.
We'll be locking down the exhibitor's list on October 1, so anyone that plans to be there should commit before then. As far as I'm concerned, manufacturers lose their bragging rights if they're not there. We've been getting very good data for the past two years, and I expect we will again this year. We're following an organized, published test plan, using a calibrated LMS system and making our measurements in a large outdoor space. I'm looking forward to obtaining useful information and having a really good time.
Post by: Ivan Beaver on September 19, 2007, 05:29:28 PM
You say that the system is calibrated, but yet the JBL 728 is measuring the same as JBL specs, but you say you were putting in 2.83V and JBL says 1Watt. 1Watt @ 4 ohms is 2V.
There was an argument that you were sure that JBL was using 2.83V and NOT 2V. But if you do the math for the numbers JBL states on their spec sheet of power Vs wattage you end up getting back to them only putting in 1W or 2V.
So my guess is that your system was off by 3dB last year. I also find it strange that you claim 108dB sensitivity for the 12 Pi,(with 2.83V input) but yet at the shootout the highest level you got was 104dB and that was at 120hz.
How do you account for the difference except that if you were to increase your measured sensitivity by 3dB (or so) like the JBL should measure, then you might be able to meat your own specs.
So my guess is a couple of things. Either your "calibration" at the shootout is off, or your spec sheet is wrong. I suspect the former.
Any thoughts?
Post by: Wayne Parham on September 19, 2007, 07:11:19 PM
The 12Pi basshorn subwoofer measured at the 2005 Prosound Shootout was a prototype, and the one measured at the 2006 Prosound Shootout was a early model production version. The response curves of the two were slightly different. I was pleased with both versions, but they are a bit different.
I did the measurements in 2005 on a calibrated LMS system. I was pleased with the quality of datasets. We got amplitude response at 28.3v/10M, 100w/10M, 200w/10M and so on, up to the maximum power limit of each speaker, when the owner said "stop". We also got THD+N distortion measurements at each power level.
David Lee did the measurements in 2006 on Praxis. If you want to know specifics about the 2006 measurements, talk to him.
This year, we'll be back to running our tests on the LMS system.
As for the rest of your comments, sounds like nothing but sour grapes. Looking back at the things you've said on this thread, it is clear that you are not objective. You are needlessly argumentative and frankly, your assessment of impedance and its relationship to voltage and power are way off base. It couldn't be more obvious that you are just trying to be disparaging. It almost looks like you're trying to find a reason not to show.
Even still, you're welcome to come to the Prosound Shootout if you're willing. Your speakers will be compared fairly with others. You can watch each measurement as it is performed, even perform the setup yourself, if you wish. This isn't about one-upmanship, it's about getting together outdoors on a nice early fall afternoon and getting the best data we can.
Post by: Ivan Beaver on September 20, 2007, 08:48:40 AM
I personally don't care if YOU are happy with the results, the measurements don't even come close-in my book.
Your comment on the prototype 12pi bing "a little" different than the production model? Do you consider 7-8dB "A LITTLE" different. I consider that to be a HUGE difference. A couple of wiggles yeah, but not that much. And what did you change in the production model to make it lose sooo much output? And why would you do that?
As I have said many times before CALIBRATE YOUR SYSTEM WITH A CALIBRATOR and do not rely on "self calibration".
Your comment about measurements being couple of dB off. What do you consider to be accurate. I wound not say anything about a dB or so difference, but 3dB is really pushing it for "being close".
When we had our mic calibrator re-calibrated (just before the NY shootout) it was out of spec from the manufacturer. That out of spec was less than .1dB, yeah 1 tenth of the db, and it was not considered accurate. You are talking magnitudes MANY MANY MANY times that, off.
I don't remember seeing you up in NY, and there were quite a few subs from major manufacturers there. I guess since there wasn't a race afterwards it lost importance
So if your measurement system is so good, then where do you get the idea to publish a sensitivity of 108dB for the 12pi? I will ignore the fact that it is above 100Hz and out of the "sub" range, just wondering where the number actually comes from. I guess the numbers just get pulled out of you know where.
The ENTIRE reluctance for Danley to show up is for a couple of reasons. As said earlier we don't want any grossly inaccurate data to be posted all over the place. As long as it is accurate, we have no problem with that, the data will stand on its own. We strive for as accurate a measurement (AND REPEATABLE BY ANYONE-with a calibrated system) as possible.
The other reason is pure business. It costs money to send product and manpower to such an event. It would be considered a waste of time and money to get in accurate data and also not having more products in attendance that would be considered "competitors" there. Your list of major manufacturers is non existent. Those are the ones that we would be interested in "competing" against. What would be the point otherwise. Time is one of the biggest issues as we are beyond swamped with work right now. There just has to be a REASON to show up.
Danley would LOVE to show up with the new TH RODS (Ridiculous Ouput Directional Sub), to put an end to the comments about who has the biggest and loudest. Yes it would be smaller and lighter than several of the others (so I guess we would lose that contest
), but by no means quieter! We are just looking for a reason to show up- NOT for a reason NOT to show up.Attendance is not up to me (although I would probably be the person there).
If you can come up with a GOOD explanation about the differences-or at least admit that there have been errors made in the past, then attendance might be considered.
It just seems really odd to me that you want to try and do things the "hard way" that have no technical merit. For example your heat soak test. Why take the time to figure (and PLEASE don't say that it really doesn't take that much time to figure it out-that is a cop out!) the impedance at 40Hz and figure the voltage required to get to 80% rated power, then readjust the system drive levels to get that. What about driver movement and cooling at 40Hz. Different cabinets will have different excursions. What is SOOOO hard about just putting in pink noise at a rated percentage and calling it a day? Of course that would require a meter that would accurately measure the amplitude of the noise voltage, and I assume nobody there has such a meter.
And again why not use a mic calibrator-like everybody else does? Seems obvious to me. Maybe I am missing something that you know and the rest of the industry doesn't?
I am in no way suggesting that anybody is cheating or ANYTHING like that. But with a measurement system of unknown calibration being constantly changed level wise with each loudspeaker, I would get real leery about the accuracy of the measurements.
I also understand your reluctance to let another manufacturer do the measurements-BUT YET that is EXACTLY what you are (and have been) doing. You DO NOT have an independent person doing it, each year there has been some affiliation with one of the manufacturers present.
Why not let someone who does this ALL THE TIME and who is concerned about accuracy do it? AGAIN it is not about cheating, just collecting accurate data, but somehow that just does not seem important, but I guess as long as "YOU" feel good, then that is what is most important. Every time somebody's name who is qualified is brought up you shoot it down "because they know Tom Danley" and have worked with him. To me that would be a good thing-maybe some of Tom has rubbed off on them-I know it has me!!!!!
Yes up in NY the room was a BIG influence on ALL of the measurements, but Mark and I took the time to make sure we had as accurate a measurement as we could possibly get under the circumstances. If you look at the TH115 measurements you will find that they correspond well (minus the room influence) with the published data. THAT is all we are asking.
OK I have had my say about what I feel. Yes I would like to be there, but justifying the expense is up to others.
Post by: Wayne Parham on September 20, 2007, 11:43:28 AM
Our measurements at the Prosound Shootout are excellent. We perform ground plane measurements outdoors with an LMS system, which is recognized as being a reliable and accurate product. Whether last year's Praxis measurements were as good as the data gathered by LMS, I don't know. But I know we'll be using LMS this year, and I'm confident in its accuracy for this kind of test.
| Ivan Beaver wrote on Thu, 20 September 2007 07:48 |
The LAST thing Danley wants is to have inaccurate data gathered by a uncalibrated rig-as your have appeared to be being posted all over the Internet. People will then use those measurements as truth, which they obviously are not. |
So how do you explain what happened in NYC? You knew the measurements taken were heavily tainted by the room, yet you still stood by them. There is no amount of calibration that could have helped you there.
As a professional, you should have warned everyone against the problems you would face before the NYC event, not afterwards when it was too late to do anything about it. Since the event was indoors in a relatively small room, you couldn't possibly make useful measurements. You should have suggested to all the participants that were planning to truck in subwoofers from around the country that this event should be a listening evaluation session only.
Did you provide this kind of guidance then? No, you did not. Where the NYC event was concerned, you happily allowed everyone to walk right into a situation that couldn't possibly allow accurate measurements. No matter what tests were performed, no matter what instruments were used, no matter how they were calibrated, you could not have gotten anything useful out of the measurements you took in NYC.
The NYC event was probably a fun, and people were able to listen to a variety of subs, which is important. But as for measurements, you got nada. That's what you're complaining most loudly about here right now. It's a huge double standard. Where the Prosound Shootout is concerned, you complain endlessly about impedance and and gating and everything you can pry upon hoping for a crack.
Your complaints now are transparent attempts to disparage our efforts and nothing more. I'm not sure why you choose to do this, but I think it's embarrassment, to tell the truth. Or maybe you just don't want your products measured outdoors, side-by-side with others. Surely that can't be it.
If you want to participate, please do. We welcome your positive efforts. If you can help make it a better event, please do. Or if you just want to show up and have your gear represented, of course you're welcome to do that. But don't just sit there and complain. It's transparent, it's divisive and it isn't productive.
Post by: Ivan Beaver on September 20, 2007, 12:02:01 PM
Yes myself and other knew that going into it that the data would not be "real" data, but should be "representative" at least between the different products attending. It was not presented as quality data anyway-never intended-never was.
As far as I am concerned it was more of a listening event than anything else and a chance to meet other labsters and mingle over a couple of days/evenings. I really enjoyed it and think that others did also and everybody got something out of it.
Just one question you have yet to anwer-How do you explain the 7-9 dB difference between the two different years with the 12pi? That is waht I would really like an answer to. Maybe that would help clear things up.
Here are the two responses-that YOU measured. The top one is '06 and the bottom one is '05
You keep saying that you are confident that the measurements were correct, yet no evidence to back it up, and lots of evidence to convince me otherwise.
Let's look at 2 freq. 50Hz In '06 it was 96dB (after adding 20dB for distance) yet is '05 it was 105dB.
Next 90 Hz In '06 it was 102dB yet is '05 it was 111dB.
I guess those are "close enough" for you, but not for me!
Curious minds are waiting---------
Post by: Claus Lindqvist on September 20, 2007, 12:30:07 PM
I hate to get involved in a fight like this, but as I have owned and used a LMS for some 15 years I have to say something.
http://www.linearx.com/products/analyzers/LMS/LMS_01.htm
The system by itself is good. I have tested it against others (APS2C, WinMLS, Clio, MLSSA, Smaart, even SpectraLAB).
How the operator uses it, is another story.
Theres stuff one can do with it, and then theres stuff one cant. Level is one of those that can be done. Distortion is one of those that cant be done accurately.
The difference between those two years. I think I read somewhere that the 06 team didnt really know if the reference was 2.83V or 1V. Assuming it was 1V, then all is good, as 20*log(2.83) is about 9 dB . . .
Post by: Ivan Beaver on September 20, 2007, 12:56:24 PM
I am not arguing the quality of the system, but like you say, rather how it is used. That is true of any measurement system.
Even with the TEF and its high degree of accuracy, you can make the levels change on the curves to read anything you want. It is up to the operator to make sure that it is right.
The other thing about the 06 measurements, lets assume that you are correct about the drive being 1V. I can't believe that no one actually MEASURED it
. What is the point of collecting data if you aren't even going to try and do it correct?The JBL 728 is measuring 3dB to low (according to JBL specs and 1W, but Wayne is positive that JBL is using 2 watts-but his math does not back that up) then that would throw the JBL reading way to high-by 6dB.
The JBL was the only product there that had any measurements published, so it is the only one that could be used as reference.
So the confusion continues-even deeper.
Thanks for your input and you might be on to something there.
Post by: Wayne Parham on September 20, 2007, 01:52:05 PM
| Ivan Beaver wrote on Thu, 20 September 2007 11:56 |
I would agree except that Wayne has insisted that it was 2.83V-repeatably. But again CALIBRATION would show that. That is my biggest beef with the way he is doing things. He refused to calibrate/measure/check etc-with an independant meter. He believe it is all "in the system". |
That's not true, and I think you know it. When I perform tests with LMS, I set the voltage with a meter. It's part of what you've complained about in this thread, that we set the drive voltage.
Your biggest beef with how I'm doing things isn't how I'm doing things at all. You just want to try and discredit our efforts.
LMS is very accurate, and it does a good job gathering useful data. Refer to the LMS manual, which shows how it is setup and used. Specific directions are given for measuring impedance, response and distortion. Also refer to our test plan, which shows what we intend to measure and how we setup to do it.
| Ivan Beaver wrote on Thu, 20 September 2007 11:02 |
Just one question you have yet to anwer-How do you explain the 7-9 dB difference between the two different years with the 12pi? That is waht I would really like an answer to. Maybe that would help clear things up. |
As I've said before, the speakers were different and the measurement system was different.
The 12Pi basshorn we measured in 2005 was a prototype, with everything built as designed. The one measured in 2006 was an early production model. Some compromises were made for construction. It's more like the LABhorn, to be honest.
We'll be bringing that model again this year. But we're working on a second version production model that's more like the original prototype. I wasn't displeased with the first production model, but I liked the prototype better. It was made as designed, and the new production model should be just like it.
I can't really say much about Praxis because I don't use it. David Lee did the measurements in 2006. I have heard conflicting opinions about it. Some say Praxis normalizes the datasets to 1.0v, not 2.83v. If so, that would make the data captured in 2006 low by 9dB. I don't know that to be true, but I know we'll be running the same 12Pi version this year on LMS as we did last year on Praxis. So we'll find out.
I think everyone assumes the data gathered by Praxis was actually normalized to 2.0v. Perhaps David had some setting that doubled the output, I don't know. That's how we labeled the charts from the 2006 Prosound Shootout, and we posted a decibel/voltage/power conversion chart to make it easy to calculate offsets to 2.83v/M or 1W/M.
| Ivan Beaver wrote on Thu, 20 September 2007 11:02 |
If you go and look at the posts for the NY shootout you will find that I did make a good stink about the quality of the measurements-MONTHS before the event. How can you say that I didn't? |
Yet you chose to participate and to publish the measurements on your website.
| Ivan Beaver wrote on Thu, 20 September 2007 11:02 |
Yes myself and other knew that going into it that the data would not be "real" data, but should be "representative" at least between the different products attending. It was not presented as quality data anyway-never intended-never was. |
I see. So you were happy sending your products out to that event, even though you knew in advance that the measurement data quality would be poor. You chose to massage the data to your satisfaction, publish it on your website and explain how that was good enough.
Yet, here, now, you complain endlessly about impedance, windowing (even though the measurements are outdoors), voltage setting or not setting, pretty much fishing for anything you think might discredit the results.
| Ivan Beaver wrote on Thu, 20 September 2007 11:02 |
As far as I am concerned it was more of a listening event than anything else and a chance to meet other labsters and mingle over a couple of days/evenings. I really enjoyed it and think that others did also and everybody got something out of it. |
That's valid, but you're the one jumping up and down about quality of measurements. I'm saying it's a double standard.
We're using LMS this year, just like we did in 2005. We're using a calibrated M51 microphone. We're sticking to the published test plan. The environment is a huge outdoor area, free of reflections. These are excellent conditions for making subwoofer measurements.
Post by: Tim McCulloch on September 20, 2007, 02:22:56 PM
When I walked into the club, I thought I was in the lobby. Nope, it was the club. I knew any measurements made there would only be valid as comparisons within the products tested, and those measurements made with a consistant input voltage. In that context (and only that context) the measurements from NYC are useful to ME. The reality of the situation is what it is. Midtown Manhattan is lacking open space and a reasonable noise floor for outdoor measurement.
The one thing that was probably useful for many in attendence was hearing these subs in a real-world environment. While our firm only occasionally does rooms the size of Club Rebel, I was able to put the products in perspective.
Paul Bell wanted to listen to subs, and he arranged all of that to share with anyone who wanted to be there. I don't think *he* intended it to be a scientific data gathering expedition.
I'll stand back from this current pissing contest except to say that any numbers from your or anyone else's testing, are to be viewed with scientific scepticism and an open ear. If *I* don't make the measurement, *I* don't truely know where the result came from. Nothing more, nothing less.
Finally, the main reason to purchase any speaker: the way it sounds. The numbers don't quantify subjective quality or suitability for a particular use. That's probably a good thing, too, or we'd have no reason to listen.
Have fun at the track. If I'm off that weekend I'll try to be there.
Tim Mc
Post by: Ivan Beaver on September 20, 2007, 04:51:16 PM
Since I had the data (I got it off Marks computer via usb drive) we put it up for people to see. Again it was never claimed to be truly accurate, and you will find may responses saying how the room dominated the response. Most cabinets just acted as pistons in the room. It was just for basic referance-nto absolute data. And for the record I assumed the room was going to be much larger than it was. I was shocked by the small size, but it was solid and tight, so that is a good thing.
Tom took the time to normalize everything to a true 1 watt measurement (based on 8 ohms impedance and the rated impedance of the cabinets there-no impedance measurements were taken). I am certain that he did an accurate job-his reputation would be on the line, but many had "issues" with that. IE: he took a 4 ohm cabinet and simply reduced the level by 3dB etc.
He is in no way desiring to "cheat" or favor one product or disfavor another, but just providing a different way of looking at the data-equally. No harm in that.
We still have the unaltered files if anybody wants them-they are in TEF format so you have to have TEF to read them.
It was just simply a "service" that many wanted that they could not get elsewhere. I do not see any harm in that. But many people do not trust ANYBODY, so there is no way to convince them.
I think I have had my say on this subject and will give it a rest, so I will not respond to this thread anymore.
Bye
Have fun at the shootout.
Post by: Tom Danley on September 20, 2007, 05:11:10 PM
You asked rhetorically “Why Danley hosted it is beyond me, simply because of the undue speculation it creates....”
Good question, in hindsight, it was apparently not a good idea to post the data.
I suggested we put it up after a long time had gone by without it being up here or anywhere else and many people here asking.
I put together the raw measurements, and a set adjusted for nominal impedance which adjusted some up and some down a few dB to approximate an equal drive power to each box. Also, I included an explanation about what I did, what I saw in the data and what I thought couldn’t be retrieved due to strong room contamination etc.
This is what Wayne refers to disparagingly saying “You chose to massage the data to your satisfaction, publish it on your website and explain how that was good enough.”
I had thought that by supplying the raw measurements AND a set adjusted for nominal equal power with a commentary and having them posted so people that asked about them could finally down load and view them, that this was actually a “good thing”.
“I'll stand back from this current pissing contest except to say that any numbers from your or anyone else's testing, are to be viewed with scientific skepticism and an open ear. If *I* don't make the measurement, *I* don't truely know where the result came from. Nothing more, nothing less.”
Sad but true AND at the same time because some loudspeakers claim 10 to 100 times more output than they actually have and some have specs that don’t resemble measured responses, it is important to measure properly if you want to find performance reality.
One of, or perhaps the very best tool there is for measuring what a loudspeaker mag/phase, is a TEF machine, you set it up properly and go and what comes out is reliable data.
Part of the thing here is history here going back even before the lab sub, Wayne has an apparent “thing” me / us to the extent that when Mark Seaton (one of the Tef operators in NY) had earlier offered to supply and run his TEF for Wayne’s past thing, Wayne declined because Mark is a friend of mine (doesn’t have any involvement at all with DSL).
Above, you have Ivan who literally has measured and aligned hundreds and hundreds of different sound systems and has been to numerous different TEF, Smaart and Synaudcon classes, trying to press a specific point about an inconsistency to a person who isn’t comfortable taking the measurements or admitting “I don’t know why”..
“Finally, the main reason to purchase any speaker: the way it sounds. The numbers don't quantify subjective quality or suitability for a particular use. That's probably a good thing, too, or we'd have no reason to listen. ”
And there you have the biggest measurement irony, measurements don’t convey what you hear, only describe what it does in one way or another under a specific condition.
Listening is what makes you smile, for me, that’s one of the best parts of my job!
Best,
Tom
Post by: Tim McCulloch on September 20, 2007, 05:56:36 PM
I have no problem with you or your products. In fact, I think you're one of the few 'for real' designers out there, and I don't think you would need to massage data in the way Wayne wants to think you did. Further, that you'd post raw and smoothed data for all to see should remove the "pay no attention to that man behind the curtain" speculation.
Alas, that doesn't seem to be sufficient.
And I was present when Mark Seaton did the TEF sweeps in NYC. I'm certainly no TEF guru, but I didn't observe anything being done that would have given your products an edge.
I'd very much like to hear the new products, and if Mike sends some to Tulsa I'll make a special effort to be there.
Have fun!
Tim Mc
Post by: Dave Rickard on September 21, 2007, 10:20:20 AM
| Ivan Beaver wrote on Thu, 20 September 2007 10:02 |
Just one question you have yet to anwer-How do you explain the 7-9 dB difference between the two different years with the 12pi? That is waht I would really like an answer to. Maybe that would help clear things up. |
| Wayne Parham wrote on Thu, 20 September 2007 11:52 |
I can't really say much about Praxis because I don't use it. David Lee did the measurements in 2006. I have heard conflicting opinions about it. Some say Praxis normalizes the datasets to 1.0v, not 2.83v. If so, that would make the data captured in 2006 low by 9dB. I don't know that to be true, but I know we'll be running the same 12Pi version this year on LMS as we did last year on Praxis. So we'll find out. |
As I was watching this thread go by, I, too, wanted an answer to the "9 dB difference" question. I don't use either measurement system, so I can't speak to the plausibility of Wayne's answer one way or the other. It does seem plausible to me.
Can anyone else help here with info about Praxis normalizing to 1.0 v?
Ivan, I know you signed off the thread, but does this "one answer" cover your "one question"? I'm not trying to restart emotions, but I'd like to see some closure on this "one issue".
Edit: Bad typing...
Post by: Wayne Parham on September 21, 2007, 01:17:02 PM
| Dave Rickard wrote on Fri, 21 September 2007 09:20 |
As I was watching this thread go by, I, too, wanted an answer to the "9 dB difference" question. I don't use either measurement system, so I can't speak to the plausibility of Wayne's answer one way or the other. It does seem plausible to me. Can anyone else help here with info about Praxis normalizing to 1.0 v? |
David Lee is a super guy, and I've always felt uncomfortable talking about the Praxis data he gathered at the 2006 Tulsa shootout. I'd feel uncomfortable talking about the Danley data gathered at the NYC shootout too, if they weren't so busy busting my balls about it.
David only got one fixed voltage sweep of each speaker and didn't run at higher power levels. There were no distortion sweeps done either. But we did get a response curve of each speaker present that year under the same conditions and at the same distance, 10 meters.
When Dave sent the data to me, there were no reference values attached to the response charts. At first, he thought they were referenced to 2.83v levels but later re-examined the data and decided they might be 1.0v levels. Upon closer inspection, it became clear the charts were normalized to 2.0v levels. Comparison with other measurements confirms this.
Perhaps David had some setting that doubled the output, or maybe he bridged amp outputs and sensed off one side only. I'm not sure, but I am confident the data is consistent and comparable to other measurements, considering a 2.0v drive level. You can use this decibel/voltage/power conversion chart to make it easy to calculate offsets to 2.83v/M or 1W/M.
One thing I am sure about is that no one has ever complained about the data from the 2005 Tulsa shootout. It was gathered with LMS using the published test plan. It's the same system and test plan we'll be running this year.
Some have said we gathered too much data, that we didn't need to do sweeps at various power levels. But I like seeing what the speakers do when pushed hard, and I like using impedance to calculate drive voltage to bring each speaker to standard power levels of 100 watts, 200 watts, and so on. We also get the 28.3v/10M value, so that lets people see a fixed voltage sweep equivalent to the 2.83v/M figure.
| Tim McCulloch wrote on Thu, 20 September 2007 13:22 |
The data from the NYC event became "Rosemary's Baby" and PSW wisely decided to not host it. Significant amounts of Monday-morning quaterbacking and speculation by non-participants pretty much doomed any useful discussion of *what was observed by the participants present.* Why Danley hosted it is beyond me, simply because of the undue speculation it creates.... |
Personally, I think the NYC event was useful as a listening session, but the data gathered was unusable. Too much room influence. I think that's probably why PSW decided not to host it.
Looking back over the discussions afterward, most looked pretty civil to me. There was some discussion about how the Danley boxes were measured, and of course, an examination of the response curves and how the room influenced them. But I don't think there was anything in the tone of the conversations that would have been considered disparaging, do you?
| Tim McCulloch wrote on Thu, 20 September 2007 16:56 |
And I was present when Mark Seaton did the TEF sweeps in NYC. I'm certainly no TEF guru, but I didn't observe anything being done that would have given your products an edge. |
I don't think anyone accused Mark, Ivan or Tom of "cheating" or taking an "edge". The big problem was the quality of data, mostly because of room influence. There were some that were uncomfortable with the way the data was handled too. That's all.
| Ivan Beaver wrote on Thu, 20 September 2007 15:51 |
The last thing I have to say is that the reason we put them up on the website is that many people were asking for the data and PSW for some reason ( I don't know why) did not want to put out a formal set of measurements. Since I had the data (I got it off Marks computer via usb drive) we put it up for people to see. Again it was never claimed to be truly accurate, and you will find may responses saying how the room dominated the response. Most cabinets just acted as pistons in the room. It was just for basic referance-nto absolute data. And for the record I assumed the room was going to be much larger than it was. I was shocked by the small size, but it was solid and tight, so that is a good thing. |
Actually, a "solid and tight" room is not what you want. Room modes are strongest in this case. If there is some loss through the walls, it will damp the modes.
I was purposely restrained on the NYC threads out of respect for your efforts. I observed the room dominating the response, but that's all.
But the room was a deal breaker, and you know it. For you to host the data from the NYC event and then to complain about the data from the Tulsa event is ridiculous, in my opinion. Certainly uncalled for, at the least.
| Ivan Beaver wrote on Thu, 20 September 2007 15:51 |
Tom took the time to normalize everything to a true 1 watt measurement (based on 8 ohms impedance and the rated impedance of the cabinets there-no impedance measurements were taken). I am certain that he did an accurate job-his reputation would be on the line, but many had "issues" with that. IE: he took a 4 ohm cabinet and simply reduced the level by 3dB etc. |
You made two dozen posts on this thread chastizing me for using measured impedance values, when you used "rated impedance of the cabinets"?!!
Your calculations were based on a figure we both know to be almost completely meaningless, basically just the nearest multiple of four ohms. Most of the subs were horns, which don't have average impedance that fits nicely as a multiple of four ohms, yet those are the kinds of figures you used to "normalize" the data.
What in the world makes you think that's a better way to do it than to measure impedance and use the minimum value in the passband?
If you measure impedance and set the drive level accordingly, you don't have to normalize your response charts. This makes all the participants comfortable, and you don't find out later, "many had "issues" with that."
| Ivan Beaver wrote on Thu, 20 September 2007 15:51 |
He is in no way desiring to "cheat" or favor one product or disfavor another, but just providing a different way of looking at the data-equally. No harm in that. |
Forget about whether there was an attempt to "cheat". That's never been in question. What is in question is the same thing you brought up earlier - "Who decides what impedance to use for determining power level?"
We use minimum impedance to determine power at the Tulsa shootout. We measure it at the Tulsa shootout, and the exhibitors all see it. We calculate the drive voltage required to deliver 100 watts to the load at its minimum impedance. This is the most conservative method, and has been shown to be within 0.5dB of average. No post-processing is required to show response charts of 100W/10M or 1W/1M.
We also measure at a fixed 28.3v. You can take these curves and manually offset them the way you did for the NYC shootout. It's fine with me, the results will be the same. Either way is fine. But you're the one complaining, not me. My complaint is with subwoofer measurements made in a small "solid and tight" room.
Post by: Dave Rickard on September 23, 2007, 02:05:13 AM
| Wayne Parham wrote on Fri, 21 September 2007 11:17 |
When Dave sent the data to me, there were no reference values attached to the response charts. At first, he thought they were referenced to 2.83v levels but later re-examined the data and decided they might be 1.0v levels. |
Or possibly some other value in between, which could explain the JBL mystery?
For the record, I'm not questioning Mr. Lee's honesty or integrity, and I'm glad he takes the time to do this event.
Good luck this year. I'd like to come but my schedule won't allow.
Post by: Wayne Parham on September 24, 2007, 11:45:04 AM
| Dave Rickard wrote on Sun, 23 September 2007 01:05 |
Or possibly some other value in between (1.0v and 2.83v), which could explain the JBL mystery? |
Exactly. It's clear the 2006 charts were normalized to 2.0v levels. Comparison with other measurements confirms this. Perhaps David had some setting that doubled the output, or maybe he bridged amp outputs and sensed off one side only.
| Dave Rickard wrote on Sun, 23 September 2007 01:05 |
For the record, I'm not questioning Mr. Lee's honesty or integrity, and I'm glad he takes the time to do this event. |
I agree. David is a good guy, and I am always glad to see him. He has been involved in every one of these things, and has always been extremely helpful. The amplifiers used each year were his, and he has always been willing to do whatever needed to be done. There is a real spirit of camaraderie and I really like that.
I wouldn't think of critiquing his measurements in 2006. I will reiterate that we used LMS in 2005 and we'll use it again this year. There was never any question about the validity or quality of data we gathered with it using the published test plan. By sticking to this plan, and making measurements outdoors, we are able to gather useful data that is very reliable, repeatable and accurate.
Post by: Tim McCulloch on September 24, 2007, 12:58:54 PM
| Wayne Parham wrote on Mon, 24 September 2007 10:45 | ||
I agree. David is a good guy, and I am always glad to see him. He has been involved in every one of these things, and has always been extremely helpful. The amplifiers used each year were his, and he has always been willing to do whatever needed to be done. There is a real spirit of camaraderie and I really like that. I wouldn't think of critiquing his measurements in 2006. I will reiterate that we used LMS in 2005 and we'll use it again this year. There was never any question about the validity or quality of data we gathered with it using the published test plan. By sticking to this plan, and making measurements outdoors, we are able to gather useful data that is very reliable, repeatable and accurate. |
Wayne-
Do you a list of confirmed products to be evaluated?
Any EAW? Any JBL? EV?
"We" can do all the boutique shootouts we want, but until the Davids (sorry Mr. Lee for the allegory) take on the Goliaths and show their stuff, it's mostly a meet and greet with numbers at the end. Perhaps Lance K can bring some of his EAW (hey, we'll clean the track dust off of 'em, Lance!).
The "big dogs" are the only ones with something to lose, and it's no surprise to me they don't want to send product and have it look bad. The only way we'll see those brands is if end users bring them.
Have fun, good luck.
Tim "remembers Lance's first PA" Mc
Post by: Wayne Parham on September 24, 2007, 02:18:59 PM
I spoke with Lance Klaurens last week about the EAW subs, and plan to see him again tomorrow. He expressed an interest on having them measured. But he has a lot on his plate, and the subs may be in use. So we'll see. David Lee and I talk pretty regularly, and last time we talked, he said the JBLs were still available. I'll confirm that this week.
Post by: Jeff Permanian on September 28, 2007, 12:02:47 AM
Post by: Wayne Parham on September 28, 2007, 11:27:23 AM
| Jeff Permanian wrote on Thu, 27 September 2007 23:02 |
Are you planning on doing a listening evaluation? I didn't see it listed in the test plan. |
You're right, Jeff, it's not listed on the test plan. The test plan is really just a list of the steps we'll take to run the LMS analyzer on each speaker. It's published to show everyone what we do and how we do it. After the tests are done, we'll listen to each speaker. At the end of the day, we'll go out to dinner and talk.
There's more information on what we'll do in the "Schedule and exhibitors" post. We'll close the list this weekend and make a specific schedule of when each speaker will be tested. I'll post that right underneath the "Schedule and exhibitors" post so you can see when you'll be up.
By the way, I spoke with David Lee and he said he sold the JBL subs, so they won't be there. Lance Klaurens wanted to bring his EAW subs, but they'll be in use so he can't. So those two subs are out. I wanted to have those for comparison, but to tell the truth, I was also concerned about time.
I'd rather have time to measure each speaker properly than to have a whole lot of speakers that we rushed through. This event was really started as a way to get useful data in an open field where we could make a lot of sound. You can't do that in the city, not even in a large parking lot. There's no way, it's too loud. So I approached the Tulsa race track about it and they agreed to let us do it. This way we are able to get really useful data without spending a lot of money.
The Prosound Shootout is really for companies like yours and mine, and all the other small sound companies out there with a dozen employees or less. Anyone smaller than JBL, EAW and Meyer can probably benefit from it, because we perform measurements that are tough to get otherwise. It provides some exposure too, because we can all look at the data afterwards and discuss it, here and elsewhere.
There's a lot of good camaraderie at the Prosound Shootout and it isn't competitive. It's really laid back and informal. The test setup is formalized, because we need a standard plan, but the feeling at the gathering is loose and informal. It's called a "shootout" only because that's what previous events were called, but it's really an information gathering session. Everyone is a winner, because everyone walks away with valuable data on their speakers that the whole world will see.
Post by: Edward Challanger on October 05, 2007, 06:37:09 AM
why you arent using a measurment system like Monkeyforest it includes all an amp etc. so its always calibrateted.
then you make the measurments in a quite area outdoors 4meters far from the box groundplane.
thats all. i think its quite simple.
perhaps you can do this in the anechodid Chamber at EAW oder at danley sound labs oder at Meyersound. or at the MIT
vx all interesing subs on the market. JBL , EAW , PI speakers etc pp.
each frim has to pay the same rate to measure their subs.
plus transport by a trucking company.
so you get true measurments.
thats an job for a student f
Post by: leon douven on October 05, 2007, 01:16:05 PM
* wayne, please put me on the list, i'm cumming too... I love to have it measured on the LMS-machine...
* ivan, better you come too, and see some real rediculous output...
* tom, could you plot the raw data again...
Leon
www.drsjaak.nl
Post by: Jeff Permanian on October 07, 2007, 12:02:15 PM
| tthorsten Thorsten Bunz wrote on Fri, 05 October 2007 05:37 |
Hey why you arent using a measurment system like Monkeyforest it includes all an amp etc. so its always calibrateted. then you make the measurments in a quite area outdoors 4meters far from the box groundplane. thats all. i think its quite simple. |
link:
http://www.monkeyforest.de/Page10383/Monkey_Forest_dt/monkey _forest_dt.html
Post by: Phil LaDue on October 07, 2007, 03:05:16 PM
http://babelfish.altavista.com/babelfish/tr
Post by: Pascal Pincosy on October 07, 2007, 04:10:37 PM
| tthorsten Thorsten Bunz wrote on Fri, 05 October 2007 11:37 |
perhaps you can do this in the anechodid Chamber at EAW oder at danley sound labs oder at Meyersound. or at the MIT |
You would need one hell of an anechoic chamber to do testing on subs. Even Meyer's anechoic chamber only has rejection down to 80Hz: http://www.meyersound.com/products/technology/chamber.htm Doesn't help much for testing subs.
Post by: Andy Peters on October 08, 2007, 04:52:49 PM
| Pascal Pincosy wrote on Sun, 07 October 2007 13:10 | ||
You would need one hell of an anechoic chamber to do testing on subs. Even Meyer's anechoic chamber only has rejection down to 80Hz: http://www.meyersound.com/products/technology/chamber.htm Doesn't help much for testing subs. |
There is an anechoic chamber at Patuxent River Naval Air Test Station is a hangar that is large enough to hold an F-14D, suspended from the ceiling, with plenty of room to walk around and under the airplane. The guys who operate the chamber like to say that it's anechoic from DC to daylight. The actual range is, um, classified. (Or so they told me when I asked.)
I'd imagine that it's good enough for subs.
-a
Post by: Pascal Pincosy on October 08, 2007, 05:11:47 PM
http://www.audiojunkies.com/blog/503/the-worlds-largest-anec hoic-chamber
Maybe we can get them to clear a couple days in their calendar
Post by: Edward Challanger on October 09, 2007, 05:05:15 AM
either a measuring system or an anechoic chamber or a person or instituit like the MIT or the Airplane guys.
here the guy form Eondaaudio her can also measure - i think quite good.
because he offersubs with a cardioid pattern.
there are only some other manufactures in the world that offer this .
Nexo, D&B, MEyersound, Cadenbach.de and Eondaaudio
some fimrs has Cardioois settings like D&Bs CSA these are Pairforce.de , tw-audio.de , D&B
all the other manufctures didnt have one.
they only built and sell normal subs without a bonus.
I think there are over 150 or 500 firms who built PA oder Studio speakers for professionals - perhaps if you count the hifi manufactures there are 50000 or more.
So just buy an other measureing system
or built things in your measureing system you can measure doubtless your and other subs in diffrent locations.
The technik to measure open air in 4meters groundplane is quite good. Always with the same amp and calibratetet so you will seh which subwoofer is the loudest on earth from 30 to 120hz.
Post by: Wayne Parham on October 09, 2007, 11:11:33 AM
We will be measuring outdoors in a large open area using LMS 4.5 with a calibrated M51 precision microphone. The method we'll use is described in the test plan.
Post by: Grant Rider on October 11, 2007, 12:07:53 PM
http://srforums.prosoundweb.com/index.php/mv/msg/24934/25264 1/0/#msg_252677
Tom Danley admits to "a certain friction which goes way back" but says he "was thinking of sending a new box (to the Tulsa sub shootout) but the first samples, while impressive sounding, were I felt too far short of the computer model".
Maybe we are seeing an end to the friction?
| Tom Danley wrote on Tue, 09 October 2007 23:49 |
I have sent speakers to shootouts before and think proper measurements and side by side comparisons vital in getting to reality. Personally Wayne and I seemed to exhibit a certain “friction” which goes way back and my daughter has surgery that weekend so I couldn’t go anyway. I was thinking of sending a new box but the first samples, while impressive sounding, were I felt too far short of the computer model. I (hope) figured out what wasn’t right and have a second set in the works. These boxes should in a stack of 4 have about 10dB of forward directivity gain in addition to sensitivity and a lower cutoff, but hey, they aren’t measured yet. |
Post by: Wayne Parham on October 15, 2007, 10:46:23 AM
Weather forecast in Tulsa on October 19th is 80
Post by: Bogdan Popescu on October 17, 2007, 04:36:29 PM
Bogdan
Post by: Edward Challanger on October 19, 2007, 10:05:36 AM
http://www.nwaalabs.com/our_services.html
Post by: Dave Rickard on October 19, 2007, 11:01:43 AM
Best wishes and good data to all.
Post by: Jeff Permanian on October 20, 2007, 05:18:29 PM
Post by: Leland Crooks on October 20, 2007, 10:59:26 PM
Leland
Post by: Wayne Parham on October 21, 2007, 01:34:21 PM
I didn't think Jeff's speakers measured poorly at all. I've measured a lot of small basshorns, and I thought the Growlers did well. Hoffman's Law tells us you have have extension, efficiency or size, but you can't have all three. A small basshorn is usually either peaky or sacrifices extension, some sacrifice efficiency. The thing is, Growlers are small enough to be easy to carry and you can group a bunch of them together to bring the efficiency up and smooth the response. It's actually about half the size of a typical double 18" sub or a medium sized basshorn, probably a quarter the size of the biggest ones. So you can get more Growlers in the same real estate.
Leland's horns measured pretty well too. I think he is used to seeing smoothed response curves, which hide the bumps on basshorns and the "grass" on top boxes. Leland's horns are Fitzmaurice designs, and they have a characteristic Fitzmaurice curve, sort of a pipe/horn. When measured in groups, they smooth out. That's how most people use horns anyway.
Leland had a leak in one of his subs, but fixed it before response was measured. He actually discovered it when we did the impedance sweep. This is one of the benefits of measuring impedance rather than depending on "advertised impedance" - It tells us things about what's going on inside the box and how our horns are operating.
I thought everyone was a winner this year. I don't say this in a "kumbaya, let's all hold our hands and get along" way - I'm saying that each horn showed specific strengths and all they all sounded good. The Growlers thumped pretty well for a small box, and were easy to carry by hand. The Fitzmaurice horns were larger but did't weigh too much and were easy to roll on built-in castor wheels. They had deeper extension, and would be able to make use of it when grouped. The BassMaxx horn thumped real well, as you would expect, and would handle a lot of power. I was very proud of my 12Pi too, as it did well. It definitely hits the low notes.
We only measured singles, and that's a worst case situation. It really shows the characteristics of each basshorn. When used in groups, ripple smooths out and the bottom end response comes up to match the top. Efficiency comes up too.
We need a full hour to do all the tests we do on LMS. We measure impedance, then sweeps for SPL and distortion at 28.3v, 100w, 200w, 400w and 800w. Some we do at 1600w as well. That's about a dozen sweeps per box, so even if we can get setup and run each test in just a couple minutes, the hour goes quick.
To measure groups, we probably need two hours for each exhibitor. That allows us another hour to move in additional boxes and do the sweeps for them.
Anyway, I've uploaded all the response charts and am now making links to each of them. I'll write back when everything is up online.
Post by: Wayne Parham on October 21, 2007, 04:36:00 PM
Measurement results from the 2007 Prosound Shootout are available now on AudioRoundtable.com and ProsoundShootout.com.
Post by: Wayne Parham on October 21, 2007, 09:50:34 PM
| Jeff Permanian wrote on Sat, 20 October 2007 16:18 |
What a disaster! We brought out some untested prototypes and they measured very poorly, decreasing 50hz and increasing 70hz. |
I thought your Growlers did pretty well. Glad you came out! Good hanging out with you.
You said the new woofer had 21mm xmax, didn't you? That's cool, I know you liked the extra excursion for operation under horn cutoff. But I wonder if it might have been better to use a woofer with about half that xmax. The long voice coil required to get the extra excursion spreads the flux over a wide area. A shorter coil would concentrate it more and could bring the efficiency up. Through the pass band, the limit would still be thermal even with half the xmax. Just a thought.
Post by: Jeff Permanian on October 22, 2007, 10:33:27 AM
| Leland Crooks wrote on Sat, 20 October 2007 21:59 |
It was a pleasure to meet you. I owe you a tube of liquid nails. Leland |
Great meeting you and everyone else.
p.s. The Growler was still +3/-3db 44-120hz.
Post by: Wayne Parham on October 23, 2007, 02:36:07 PM
| Jeff Permanian wrote on Mon, 22 October 2007 09:33 |
The Growler was still +3/-3db 44-120hz. |
Yes it was. We measured a couple other subs about the same size on previous years, namely Cerwin Vega L36 and Fitzmaurice T24. I think each of these is about 8ft3. Check 'em out for comparison:
Post by: DAVID_L_PERRY on October 24, 2007, 03:41:09 AM
I have a pair of Titan 48's and although I cant hear any leaks, (tested with a 25hz source) I am interested in a more accurate test method.
Many thanks, Dave Perry
Post by: Iain_Macdonald on October 24, 2007, 10:16:52 AM
There are a number of different ways. I don't know what test gear you have. But this ProSoundWeb educational article is a good start.
http://www.prosoundweb.com/install/sac/n26_4/zrta/zrta-1.sht ml
Iain.
Post by: Wayne Parham on October 24, 2007, 11:23:48 AM
Impedance is actually pretty simple to measure with a sine wave generator and an oscilloscope or good AC voltmeter.
If using a meter, be sure it is one that is accurate at frequencies other than 50/60Hz. If you don't have a tone generator, you can download a sine wave generator that works with most sound cards. Here are some examples:
Connect the speaker to the sound card through a fixed series resistor. You'll probably want a value between 100Ω and 1kΩ, although other values can also be used. You should know the value of the resistor very precisely. The more accurately you know the value of the resistor, the more accurate you'll be able to calculate the value of your speaker's impedance.
Set the tone generator for a specific frequency and measure the voltage across the resistor. Using Ohm's Law, calculate the current flowing through the resistor using the known values of resistance and voltage across the resistor:
I = E/R
Now measure the voltage across the voice coil. Knowing the current through the circuit, you can calculate the impedance of the voice coil:
Z = E/I
You can make a plot of impedance values at various frequencies in the passband. Just take your time and step through some frequencies, measuring voltage and calculating impedance for each one.
Note: Do not depend on the voltage across the voice coil to be the difference between source voltage and the drop across the fixed series resistor. It will only be that when the impedance of the voice coil is purely resistive, which only happens at a few frequencies at best. Most times, the voltage across the voice coil and the voltage across the resistor are out of phase, and so cannot be added as a scalar.
Phased voltages are vector values, so adding them together as scalars doesn't make sense. To demonstrate, let's say you have two 10v signals that are 180
Post by: Les Webb on October 24, 2007, 09:29:15 PM
Impedance sweeps are the end all for telling air leaks, Leland was surely not unaware of this, just caught without something to fix the leak, for which he was really glad that Jeff let him borrow some
. Thanks Jeff.The t48s tested like we expected, they were optimized for 40hz up. When adjusted for impedance and pack space I think they faired very well with the larger boxes.
Thanks once again Wayne for putting on a top notch shootout. I WILL be there next year with some T-36s and maybe some other Fitz designs.
Les
Post by: Wayne Parham on October 25, 2007, 01:25:41 AM
| Les Webb wrote on Wed, 24 October 2007 20:29 |
The t48s tested like we expected, they were optimized for 40hz up. When adjusted for impedance and pack space I think they faired very well with the larger boxes. |
There's no need to adjust for impedance because we measured it. We ran sweeps at a constant 28.3v, and also at 100w, 200w, 400w and so on. Compare charts at constant power and there is no need to adjust for impedance.
Looking over the charts on the Fitzmaurice website, I'd say they are pretty close on SPL but somewhat off on response shape. They're smoothed like what I'd expect to see in groups of six to eight, even when a single horn is shown. The Fitzmaurice flare shape seems to result in a pretty consistent response curve, and that is not apparent on the Fitzmaurice website.
The Tuba 36 we measured had a similar curve as I recall. Some have said it was because the driver chosen was not right for the horn, and that may be. But I do see some similarity in the response curve shape of all the Fitzmaurice basshorns we've measured.
Post by: Pascal Pincosy on October 30, 2007, 12:59:03 AM
Post by: Wayne Parham on October 30, 2007, 01:58:29 PM
I wished we had measured groups of horns too. At least two, maybe four or more. We just flat ran out of time. Next time, we'll probably reserve two hours per exhibitor rather than just one hour.
Post by: Grant Rider on November 01, 2007, 01:20:35 AM
| Wayne Parham wrote on Tue, 30 October 2007 17:58 |
I wished we had measured groups of horns too. At least two, maybe four or more. We just flat ran out of time. Next time, we'll probably reserve two hours per exhibitor rather than just one hour. |
Judging from previous shootouts, I think you can just add 3db to the charts to calculate for two boxes. 6db if you don't correct for the parallel connection cutting impedance in half. The charts get a little smoother too.
By the way, nice job. Thanks for doing the shootout. Kudos on the push pull idea too, it definitely drops the distortion waaaay down.
http://srforums.prosoundweb.com/index.php/m/257706/25195/0// /15858/#msg_257706
Post by: Wayne Parham on November 01, 2007, 10:58:19 AM
| Grant Rider wrote on Thu, 01 November 2007 00:20 |
Judging from previous shootouts, I think you can just add 3db to the charts to calculate for two boxes. 6db if you don't correct for the parallel connection cutting impedance in half. The charts get a little smoother too. |
That's true. We would have liked to measure pairs and groups of four, but we were pressed for time. This lets us see response in groups, which is a little different than just increasing SPL. Basshorns are almost always acoustically small, so grouping them helps make them more efficient. It not only increases SPL but also tends to reduce response ripple.
We were going to measure with voltage constant, so that would have added 6dB. In other words, when measuring pairs, we would send 28.3v to each box, then 100 watts to each box, and so on. Sending 100 watts to a pair of boxes is 200 watts total, of course, which is 3dB greater than 100 watts total. If a person wanted to compare a single cabinet to a pair of smaller cabinets, they could easily view the data in many ways, say comparing charts measured with 200 watts on a single cabinet against 100 watts per cabinet for a pair.
| Grant Rider wrote on Thu, 01 November 2007 00:20 |
Kudos on the push pull idea too, it definitely drops the distortion waaaay down. http://srforums.prosoundweb.com/index.php/m/257706/25195/0// /15858/#msg_257706 |
It does reduce distortion, that's for sure. A basshorn with two woofers should always be configured push-pull, in my opinion. This configuration has proven to be extremely effective at reducing distortion, as you can clearly see from the measurements. The biggest improvements are in the bottom octave, where distortion of most subs goes off the charts. Most subs (even basshorns) have distortion that rises above the fundamental down near cutoff. The 12Pi basshorn subwoofer doesn't do this, in fact, distortion at the low cutoff is no higher than anywhere else on the response curve. It's down near the noise floor level all the way across the curve, even at very high output levels.
Post by: Grant Rider on November 02, 2007, 10:07:00 PM
Charts in the road test forum show the 2007 and 2008 models
Charts on the prosound shootout website show the third version
What is the difference between each of these three models? Does each have a different woofer inside? Why were the changes made? What are the strengths and weaknesses of each version?
Post by: Tom Danley on November 04, 2007, 08:18:03 PM
I have to take a small issue with a statement here, as it is misleading.
“This configuration has proven to be extremely effective at reducing distortion, as you can clearly see from the measurements.”
Technically speaking one couldn’t possibly draw that conclusion, in order to see how effective the push pull arrangement is, one would have to compared the same horn shape but not in push pull. Comparing different horns with different drivers tells you nothing about the value of push pull vs standard mounting.
As you might be aware, at the Michigan subwoofer shoot out, where the labs were measured, they had the lowest distortion of all the speakers there. (look up the curves on line). That same driver linearity is how people have been able to use them in living rooms eq’d to extend the bottom.
Have you built and measured a 12 pi that wasn’t in push pull to see how much difference it actually makes when “that” is the only thing different? (The proper way to isolate and evaluate the effect)
Keep in mind, P/P doesn’t reduce the distortion that sounds bad, only the 2nd Harmonic produced by the driver.
Tom
Post by: Wayne Parham on November 04, 2007, 10:37:01 PM
| Tom Danley wrote on Sun, 04 November 2007 19:18 |
Comparing different horns with different drivers tells you nothing about the value of push pull vs standard mounting. |
I wouldn't say it tells me "nothing" but I would agree that it would be best to compare a horn made exactly the same as a 12Pi but without push-pull drive. I will say that with all the horns we've measured, the 12Pi has consistently shown much lower distortion, especially at frequencies near horn cutoff and below.
| Tom Danley wrote on Sun, 04 November 2007 19:18 |
As you might be aware, at the Michigan subwoofer shoot out, where the labs were measured, they had the lowest distortion of all the speakers there. (look up the curves on line). That same driver linearity is how people have been able to use them in living rooms eq’d to extend the bottom. |
Could you please provide a link to that data? Was it done at power levels like what we did in Tulsa? Was it done outdoors? I hope so, because I'd like to see more measurement data on a LABhorn. All I've seen was one chart that shows SPL at a very low drive level. I keep thinking someone will bring a LABhorn to one of the Tulsa shootouts, but so far no one has yet.
I expect the distortion characteristics of a LABhorn to be similar to other basshorns, which is to say they will rise as frequency drops, and that at high power levels they'll be louder than the fundamental near cutoff and below. For the LABhorn, what I'm calling "high power" would be about 40v, which is roughly 800 watts. Even at just 20v, I'll bet LABhorn distortion at 30Hz is only about 10dB lower than the fundamental, which is 30% distortion. I'm also sure distortion is actually higher than the fundamental at 20Hz. I can find nothing to make me believe otherwise.
What do you expect from a LABhorn, with regard to distortion? Do you have any measurements to quantify distortion performance at various power levels?
You mentioned EQ'ing the LABhorn to extend the bottom. Are you still suggesting that this be done to use the LABhorn below 30Hz? Do you think LABhorn distortion will be low at frequencies below 30Hz? Or do you just think that people won't know the difference, that they can listen to the second and third harmonics and be happy?
| Tom Danley wrote on Sun, 04 November 2007 19:18 |
Have you built and measured a 12 pi that wasn’t in push pull to see how much difference it actually makes when “that” is the only thing different? |
I plan to do that in the next few months. I'm actually making a new horn prototype, and in the process of doing so I'll be able to take parts of it to do the exact test you're talking about. I can make the equivalent of a 12Pi without push-pull drive from it.
Care to place a wager with me on the results? I'll bet it confirms once again how the 12Pi push-pull drive is what is responsible for its ultra-low distortion at low frequencies and high power levels.
Post by: Wayne Parham on November 05, 2007, 03:57:03 AM
| Tom Danley wrote on Sun, 04 November 2007 19:18 |
As you might be aware, at the Michigan subwoofer shoot out, where the labs were measured, they had the lowest distortion of all the speakers there. (look up the curves on line). That same driver linearity is how people have been able to use them in living rooms eq’d to extend the bottom. |
I did a quick search of the internet to find the distortion measurements from the Michigan shootout in 2003. There are some differences between the Tulsa data and the Michigan data that make this less than an "apples to apples" comparison, but I think it is still good information.
The graph below is distortion of four LABhorns measured with "9-12 volts input". I'm not sure why the voltage wasn't recorded more precisely than that, but in any case, that's less than 40 watts.
Since the LABhorn presents about 4Ω load impedance, 9 volts is 20 watts and 12 volts is 36 watts. We're only talking about 10 to 20 watts per woofer being sent for the distortion measurements. I wouldn't expect much distortion at these power levels, because they're so low.
Having four horns is an advantage too, since loading is better at low frequencies than what you would get having just one horn. So again, this comparison heavily favors the LABhorn, with the very low drive voltage and the use of four horns instead of just one.
As you can see, even at just 10v, distortion at 25Hz is already at 10%, rising rapidly at frequency falls. As one would expect from a basshorn, it is lowest in the passband, but rises rapidly at the cutoff frequency. From 35Hz down, distortion ramps up heavily, already above 3% at 30Hz even at the low drive level of 10v. By 20Hz, it is at 30% distortion, again, at only 10v input signal.
These figures aren't unexpected. If you double the drive signal, you'd see that distortion would be louder than the fundamental at 20Hz, probably also at 25Hz. At 30Hz, distortion might be about equal to the fundamental, or maybe slightly less. If you increase drive even more, nearing maximum power, distortion of the LABhorn would be even worse. This is no slam of the LABhorn, all basshorns are like this. They work best when used in their passbands, and as you get close to their lower cutoff frequency, distortion rises rapidly. That's just the way it is.
Except for the 12Pi with its push-pull drive. Look at the charts below. The blue line is SPL and the violet line is distortion. This is a single horn, run at 28.3v - three times the drive voltage as was used to test a group of four LABhorns.
Notice that distortion doesn't rise at low frequencies like it does on other basshorns without push-pull drive. This makes a cleaner, tighter sounding bass. Everyone notices it right away. The distortion is so low at this 28.3v drive level that we really can't see it - it's mostly below the noise floor.
The distortion curve is shown in decibels, and to convert these values to percentages use the chart at the link below. The noise floor was about 70dB, so anything below that is indeterminate.
Now the real nut cutter. How does it perform at higher power levels? See the link below:
Post by: Tom Danley on November 05, 2007, 08:30:55 AM
It is unfortunate that an apples to apples comparison is not possible here, however it is worth looking a little further.
Another thing to keep in mind is how the distortion is displayed is different in the two systems (as a fraction and relative to the fundamental).
As one can read directly, the Labs measured around 3 / 10 of one percent down to about 35Hz.
With the 12pi being driven harder and measured differently, isn’t a direct comparison.
Several spot frequency comparisons the pi shows a difference between distortion and fundamental of about 40dB in the 80-100Hz area or about 1%.
At 30Hz, the Pi distortion has risen to about 10%, to more than 30% at 20Hz and distortion equals fundamental around 15Hz.
Tom Danley wrote on Sun, 04 November 2007 19:18
Have you built and measured a 12 pi that wasn’t in push pull to see how much difference it actually makes when “that” is the only thing different?
”I plan to do that in the next few months. I'm actually making a new horn prototype, and in the process of doing so I'll be able to take parts of it to do the exact test you're talking about. I can make the equivalent of a 12Pi without push-pull drive from it.
Care to place a wager with me on the results? I'll bet it confirms once again how the 12Pi push-pull drive is what is responsible for its ultra-low distortion at low frequencies and high power levels.”
Wayne, the driver is the primary source of distortion in bass horns, which is how BT-7’s can be less than few% at rated power and why the labs were the lowest distortion when measured so far.
I don’t see “ultra low” distortion levels in what you posted and besides, push pull ONLY reduces one distortion component and its not one that sounds bad.
Tom
Post by: Wayne Parham on November 05, 2007, 12:06:07 PM
| Tom Danley wrote on Mon, 05 November 2007 07:30 |
With the 12pi being driven harder and measured differently, isn’t a direct comparison. Several spot frequency comparisons the pi shows a difference between distortion and fundamental of about 40dB in the 80-100Hz area or about 1%. At 30Hz, the Pi distortion has risen to about 10%, to more than 30% at 20Hz and distortion equals fundamental around 15Hz. |
That's not true. The chart I displayed was done at 28.3v (over 200 watts) and at that level, you can't see the distortion present because it is below the noise floor. I guess you missed that I said the noise floor was about 70-75dB. So unless the distortion rises above that level, you can't see it.
You can clearly see distortion when it rises above 75dB though, as it does in other basshorns without push-pull drive.
| Tom Danley wrote on Mon, 05 November 2007 07:30 |
Wayne, the driver is the primary source of distortion in bass horns, which is how BT-7’s can be less than few% at rated power and why the labs were the lowest distortion when measured so far. |
Driver non-linearity is the primary source of distortion in basshorns, and this is exactly what push-pull drive corrects. The LABhorn has no mechanism to counter this kind of distortion at low frequencies.
The Michigan measurements of a group of four LABhorns run at a mere 25 watts show that the LABhorn generates more distortion than a 12Pi does when run at ten times that much power. The LABhorn was run at a flea-power 25 watts, yet it still displayed measurable distortion particularly at low frequencies. That's why I've said I don't think it's a good idea to bump up the 20Hz EQ on LABhorns. Distortion goes through the roof at those frequencies.
12Pi distortion stays under 1% - in most cases, below the noise floor and unmeasurable - until power is increased to several hundred watts. In Tulsa, we started our measurements at 100 watts and went up from there. In the 12Pi measurements, You can't even see the distortion until power is high, because it's below the noise floor.
To illustrate, let's take the measurements on the other end of the scale, where distortion is at its worst. You really have to hit the 12Pi's with several hundred watts before distortion starts to creep up above the noise floor. So lets look at the 12Pi chart taken at 1600 watts:
Now you can see some distortion rising above the noise floor. See down there at 10Hz? It has started rising there. You also see some at 30Hz and 50Hz, about 20dB below the fundamental, which is about 10%. So by 1600 watts, we're seeing 10% distortion. It stays under 10% down all the way to about 20Hz, where it finally rises. Below 20Hz, the horn is actually very quiet, there's not much output either fundamental or distortion, but as you can see from the chart, at 1600 watts, you don't want to push 10Hz through them. That's not what they're designed for anyway.
Now let's compare that to LABhorns, shall we? We can't do the same 1600 watt sweep we did in Tulsa, because LABhorns won't survive it. Not a single sweep. If you set the amplifier voltage for 65v and run a sweep, you'll smoke the drivers before the sweep ends. Without cooling plugs, the LAB12's just won't survive it. I know, I've tested these things a lot, and the stock LAB12 just won't do it.
But we can run the sweep at 800 watts. That would be fine for comparison. I expect you must have some measurements of the LABhorn at high power levels somewhere. Please dig them out and display them. They aren't available online anywhere, but you must have some. Please post them at your earliest convenience.
Post by: Tom Danley on November 05, 2007, 02:58:24 PM
Perhaps there is some confusion about what the two different types of distortion measurements show.
“Now you can see some distortion rising above the noise floor. See down there at 10Hz? It has started rising there. You also see some at 30Hz and 50Hz, about 20dB below the fundamental, which is about 10%. So by 1600 watts, we're seeing 10% distortion. It stays under 10% down all the way to about 20Hz, where it finally rises”
In a measure like your 1600W rating, where the distortion is shown relative to the fundamental and not as a percent, I get different numbers.
For example at 50Hz, its about 10%, at 30Hz, one has about 15 dB between them (about %17) and at 20Hz its about 4dB or about 40%.
If your plot were done as “percent” instead of dB difference, it would also tip up at the bottom end like the Lab subs.
“I expect you must have some measurements of the LABhorn at high power levels somewhere. Please dig them out and display them. They aren't available online anywhere, but you must have some. Please post them at your earliest convenience.”
Actually I have never built any or measured any myself. I had enough “mileage” in the software designing horns to know what needed to be done and specify a proper driver without building one. I only needed to measure the driver.
With both the Lab and your pi, it is the driver / horn alignment that makes it good.
With the push pull thing as well as what you believe to be the result of the cooling plugs, a proper or scientific comparison requires that one compare with only one thing different.
You can’t compare to a different horn and different driver and conclude the difference is “push pull”. Your non-push pull pi, if otherwise identical should actually show what difference it really makes. Keep in mind, when measured side by side with other boxes, so far, the labs have had the lowest distortion, it is after all mostly the driver and loading ratio.
As for the plugs, same thing, you have to compare them in use with only that being the difference.
It is possible I suppose but unlikely I would think that you have discovered something that bypasses the nature / speed of the temperature rises and transfer mechanisms described here. Look how fast the coil can heat up relative to the metal bits.
http://klippel.net/pubs/Klippel%20papers/Nonlinear_Modeling_ of_Heat_Transfer_03.pdf
Tom
Post by: Jeff Babcock on November 05, 2007, 04:34:04 PM
Best regards to you both!
Jeff
Post by: Wayne Parham on November 05, 2007, 04:52:28 PM
At the 2007 Prosound Shootout, our noise floor was 70-75dB. This limited our distortion resolution to about 1%, depending on the SPL of the box tested. If a cabinet produced 110dB, then the lowest distortion we could measure was 1%, at 115dB, 0.5% could be reliably detected. But if only 90dB, then the lowest level distortion you could see was 10%. So whatever SPL level you see on the response curve for any given box, that sets the resolution of distortion that can be measured at that particular frequency. As a result, the resolution is greatest in the passband, less at the lower frequency limits.
All measurements were taken with the microphone 10 meters away. We could have increased resolution of our distortion measurements by moving the microphone closer. This would increase the signal-to-noise ratio, and would have allowed us to see distortion at lower power levels, like 25 watts. But this was a Prosound Sub Shootout, not a single-ended triode shootout. We weren't interested in what these speakers do at 25 watts. All the subs we measured would do pretty well at such small signal levels. There's no challenge in that.
The information we gathered at the Prosound Shootout tells us what the subs would do at power levels they will be used at, at least a hundred watts, up to several hundred watts to the maximum rating of each sub. Even the best subs generate double-digit distortion figures at low frequencies and high power levels. Most subs generate triple-digit distortion figures, with distortion higher than the fundamental at the lowest frequencies. So even with resolution dropping at the lowest frequencies because of the reduced SPL (signal-to-noise), we still could see distortion at high power levels at sub-30Hz frequencies on all boxes but one. It isn't difficult to draw a conclusion from that.
| Tom Danley wrote on Mon, 05 November 2007 13:58 |
For example at 50Hz, its about 10%, at 30Hz, one has about 15 dB between them (about %17)... |
That's right. At 1600 watts, the 12Pi measurements show about 10% distortion and maybe a smidge more at 30Hz, still less than 20%.
| Tom Danley wrote on Mon, 05 November 2007 13:58 |
...and at 20Hz its about 4dB or about 40%. |
No, the distortion at 20Hz is below the noise floor and so we can't reliably determine what it is. The noise floor was 70-75dB, and output of both the fundamental and harmonics is falling below 30Hz, so distortion becomes indeterminate at that frequency because it is below the noise floor. My guess is distortion at 20Hz is about 20%, maybe 30% at 1600 watts. Even if it is 40%, just under the noise floor at that frequency, it would still be impressive. Most hornsubs are well into triple-digit distortion when run that far below cutoff at full power.
Look at that squarely, Tom. We're talking about a 12Pi basshorn sub generating 30% or maybe 40% distortion at 20Hz at 1600 watts. What we've seen from the Michigan sub shootout is that a group of four LABhorns generates 30% distortion at 20Hz with only 25 watts input. That means even by your own characterization of the data, the 12Pi basshorn subwoofer running full tilt at 1600 watts produces no more distortion than a LABhorn sent a mere 25 watts.
At 1600 watts, distortion of a LABhorn at 20Hz will be far higher than the fundamental. Sorry, I misspoke. At 1600 watts, output from a LABhorn will be zero after about the first half of the sweep because the voice coil will have burned open. But at 800 watts where it can survive the sweep, the harmonics will be far louder than the fundamental at 20Hz.
What would be really nice is to see a LABhorn measured at 100 watts, 200 watts, 400 watts and 800 watts. Knowing what it does at 25 watts tells us very little, particularly in terms of distortion, power compression, electro-mechanical parameter shifts and the ripples in response caused by parameter shifts at high temperatures / power levels.
| Tom Danley wrote on Mon, 05 November 2007 13:58 |
Actually I have never built any or measured any myself. |
Post by: Al Limberg on November 05, 2007, 05:28:02 PM
Not to throw a monkey wrench into things, but as probably the first person to actually complete and put Labs into use on a regular basis, I must say I have never seen anyone recommend running them below 28-32hz for pro use, even in groups of four or more. I don't doubt for a second that the drivers would self destruct at 800 watts input, or even less with a 20hz sine wave sweep. Then again, I don't expect a Porsche pancake six would make it a quarter million miles in a Kenworth hauling a fullload.
It just doesn't make alot of sense to me. Talk of eq'ing the Labs to 20 hz was always in the context of home theatre and frankly, a 20hz sinewave at even 50 watts would have earned me castration from the ex back in the day!
One other point - as a participant at the Michigan shootout, to the best of my recollection all tests were done on single cabinets other than listening tests when we cranked up 4 Labs and the pair of David's Bassmaxx cabs and perhaps 4 of our host's modified MT quad 18 cabs along with a pair of TD1s. I could be wrong. At the first shootout, our dear friend Too Tall had Murphy as his chief assistant, and even he may have been of more help than me! On the other hand, even then a good deal was learned including some guidelines of how to run future shootouts.
Best to all,
Al
Post by: Wayne Parham on November 05, 2007, 06:06:15 PM
| Jeff Babcock wrote on Mon, 05 November 2007 15:34 |
Thanks both to Tom and Wayne for your "debate", any time these ensue they prove to be highly informative. |
I hope our back and forth discussions are productive for he and I and everyone else, and not boring to people. The only thing we have to be careful of is the tendency to fall into a pattern of saying the same things over and over again. When you're passionate about something and really sure you're right, it's easy to get into that mode.
| Jeff Babcock wrote on Mon, 05 November 2007 15:34 |
Thanks Tom for that Klippel link. |
It is a great link:
- Nonlinear Modeling of the Heat Transfer in Loudspeakers, by Wolfgang Klippel
Heat is also radiated from the voice coil into the magnet, and there is direct heating of the pole piece and magnet through eddy currents. That's why removal of the heat using a cooling plug is very beneficial, especially in systems like basshorns where excursion is reduced and so forced air convection is too.
The vent in a woofer isn't just there for cooling, but also to prevent pressure from building up behind the cone. This can cause harmonic distortion because it can introduce asymmetrical cone motion. So even if cooling vent air is stalled by a basshorn limiting excursion, it is important that the vent be there for other reasons.
Here's another good link:
- Loudspeaker Power Handling Vs. Efficiency, by Rod Elliot
Removing heat from the pole piece doesn't require any tuning. All you need is a good conductor having large surface area contact with the pole piece. If you measure a speaker and find the magnet and pole piece get very hot, it's probably a good idea to add a cooling plug and a heat sink of some sort. For loudspeaker motors, heat is not your friend.
Post by: Tom Danley on November 05, 2007, 06:41:35 PM
“At the 2007 Prosound Shootout, our noise floor was 70-75dB. This limited our distortion resolution to about 1%, depending on the SPL of the box tested. If a cabinet produced 110dB, then the lowest distortion we could measure was 1%, at 115dB, 0.5% could be reliably detected. But if only 90dB, then the lowest level distortion you could see was 10%. So whatever SPL level you see on the response curve for any given box, that sets the resolution of distortion that can be measured at that particular frequency. As a result, the resolution is greatest in the passband, less at the lower frequency limits.”
Its too bad you didn’t use a TEF machine, they have superb noise immunity and it doesn’t suffer from these severe limitations.
“The information we gathered at the Prosound Shootout tells us what the subs would do at power levels they will be used at, at least a hundred watts, up to several hundred watts to the maximum rating of each sub. Even the best subs generate double-digit distortion figures at low frequencies and high power levels. Most subs generate triple-digit distortion figures, with distortion higher than the fundamental at the lowest frequencies.”
Ah, duh. Why do you think I have been making horn loaded subwoofer that have low distortion for a living 20 odd years.
“Look at that squarely, Tom. We're talking about a 12Pi basshorn sub generating 30% or maybe 40% distortion at 20Hz at 1600 watts. What we've seen from the Michigan sub shootout is that a group of four LABhorns generates 30% distortion at 20Hz with only 25 watts input. That means even by your own characterization of the data, the 12Pi basshorn subwoofer running full tilt at 1600 watts produces no more distortion than a LABhorn sent a mere 25 watts.”
Look at it squarely Wayne, until you actually measure labs side by side or make your modified pi, you have not demonstrated anything that says the push pull arrangement is responsible for what you measured.
You can’t compare your box to other horns with other drivers and conclude the reason for low distortion is “push pull”.
You can’t disregard your measurements on one hand and then use it on the other.
You also keep bringing up eq’ing below cutoff, like Al said, this has always been in regard to home use. In live sound one normally puts high pass filter at the corner, not boost it.
Normally, a measurement like yours would have used a tracking filter to extract harmonics. I suspect it is showing the proper thing where at 10Hz, the distortion has risen 10-15dB above the fundamental.
Push pull only reduces the 2nd harmonic while drivers tend to produce mostly third, which (like harmonics other than the second) are not reduced by push pull.
I am curious what you actually see when you build your non-push pull 12pi to compare to.
“Tom Danley wrote on Mon, 05 November 2007 13:58
Actually I have never built any or measured any myself.”
Yes Wayne. I designed this stuff most of my life and don’t t need to build a simple bass horn to know how it would work, that’s my computers job.
Tom
Post by: Wayne Parham on November 05, 2007, 07:11:34 PM
| Al Limberg wrote on Mon, 05 November 2007 16:28 |
as a participant at the Michigan shootout, to the best of my recollection all tests were done on single cabinets other than listening tests when we cranked up 4 Labs and the pair of David's Bassmaxx cabs and perhaps 4 of our host's modified MT quad 18 cabs along with a pair of TD1s. I could be wrong. |
I pulled the information off this site:
Way down at the bottom, in the data section, there's a link called Al's four LAB subs (3.08MB). Is that yours? When I click on it, it downloads a compressed archive with the measurements inside. Also inside is a document caled "Lab sub Al.doc" that says "All acoustic measurements done on a block of four cabinets." That's where I got the information.
Post by: Wayne Parham on November 05, 2007, 07:31:35 PM
| Wayne Parham wrote on Mon, 05 November 2007 11:06 |
Look at that squarely, Tom. We're talking about a 12Pi basshorn sub generating 30% or maybe 40% distortion at 20Hz at 1600 watts. What we've seen from the Michigan sub shootout is that a group of four LABhorns generates 30% distortion at 20Hz with only 25 watts input. That means even by your own characterization of the data, the 12Pi basshorn subwoofer running full tilt at 1600 watts produces no more distortion than a LABhorn sent a mere 25 watts. |
| Tom Danley wrote on Mon, 05 November 2007 17:41 |
Look at it squarely Wayne, until you actually measure labs side by side or make your modified pi, you have not demonstrated anything that says the push pull arrangement is responsible for what you measured. |
OK, Tom, so why do you think a group of four LABhorns generates 30% distortion with only 25 watts input, yet a single 12Pi basshorn produces no more than that at 1600 watts?
Post by: Al Limberg on November 05, 2007, 09:52:59 PM
I guess maybe I'm still a little slow on understanding why we are making such a big deal out of distortion figures outside of the design parameter of the speakers in question. I suspect I'd have a hard time calling Jerry McNutt my friend if I ran my LABs with an HPF at or below 20hz. Methinks he might shuffle my emails off to the junk bin and place my phone calls on permanent hold.
Al
Post by: Antone Atmarama Bajor on November 05, 2007, 11:25:21 PM
Did you do any 3rd Harmonic Sweeps Wayne???
The Second Harmonic is quite simply the Octave, so it will always be Consonant, and less noticeable. 3rd on the other hand is more of a problem and can cause dissonance. Push pull does not help here. So the push pull may give superior results at reducing
2nd order HD but not Odd, I'm not sure if it does anything for the other Even Harmonics.
Antone-
Post by: Wayne Parham on November 06, 2007, 03:16:35 PM
| Al Limberg wrote on Mon, 05 November 2007 20:52 |
Hmmm, It has been nearly 5 years (hard to believe!) but I would be nearly willing to bet that the distortion measurements were made with a single LAB since we only had individual samples of the two Community cabs and pairs of the BassMaxx offerings. Perhaps John Halliburton or Paul Bell or David would be able to confirm or correct my supposition. I'll definitely call and harass Too Tall tomorrow. |
Might be interesting to find out. I just quoted what I saw on the Michigan Subwoofer website. Even if we are talking about only one box though, we can still see pretty clearly that the LABhorn has the same distortion at 25 watts that the 12Pi has at 1600 watts.
| Al Limberg wrote on Mon, 05 November 2007 20:52 |
I guess maybe I'm still a little slow on understanding why we are making such a big deal out of distortion figures outside of the design parameter of the speakers in question. |
The reason is Tom jumped in on this thread (and many others) to say push-pull drive used in the 12Pi basshorn sub doesn't work. I don't see how he can look at the data and come to that conclusion. The evidence is overwhelming that it does.
Tom claims that the LABhorn measures lower in distortion. He later admitted that he had never measured one, so I don't know why he ever said anything in the first place. There was no hard evidence to make any assertion as forcefully as he has done. The only data I've seen of LABhorn distortion was made with only 25 watts input power. That's not pushing it very hard, really. We need to see what the LABhorn does at 100 watts, 200 watts 400 watts and 800 watts. These higher power levels are where the rubber hits the road.
Even with just the 25 watt chart, we can clearly see a difference in the LABhorn and the 12Pi basshorn subwoofer. Where the distortion rises below 35Hz in the LABhorn, it rises much more slowly in the 12Pi. The same distortion you're getting from LABhorns at 25 watts, you don't see in the 12Pi until it reaches 1600 watts. That's pretty significant, don't you agree?
The push-pull arrangement is most effective at very low frequencies. It is designed to be of most benefit near cutoff, where the horn is starting to lose its ability to load the cone. It does that beautifully, as the data clearly shows.
After looking at this data, I can find absolutely no reason to make a basshorn with two woofers without configuring them in a push-pull arrangement. In any installation where more than one woofer is used, I would suggest that they be done in push-pull pairs.
| Antone Atmarama Bajor wrote on Mon, 05 November 2007 22:25 |
And what harmonic is being tracked, I would think its probably 3rd Harmonic. |
At the Prosound Shooutout, the way we measured distortion was to track the fundamental and bandstop it, bandpassing the two octaves above it. That way we got the 2nd and 3rd harmonics. The window is rather wide though, so it can "see" a lot of noise too. That's why we call it a THD+N measurement, because I think most harmonics from loudspeakers are 2nd and 3rd and because noise is included in the data.
| Antone Atmarama Bajor wrote on Mon, 05 November 2007 22:25 |
The Second Harmonic is quite simply the Octave, so it will always be Consonant, and less noticeable. 3rd on the other hand is more of a problem and can cause dissonance. Push pull does not help here. So the push pull may give superior results at reducing 2nd order HD but not Odd, I'm not sure if it does anything for the other Even Harmonics. |
The thing is, the second harmonic falls within the passband of the horn. Since horn output is strong to about 180Hz, second harmonics of fundamentals up to 90Hz are acted upon by it. Basically, the whole usable range of the sub is vulnerable to second harmonic distortion generated by the woofers. As much as possible, the drive units should be made free of second harmonics.
The third harmonic is higher in frequency, so the low pass function of the front chamber and horn folds serves to attenuate it. Since horn output starts to fall above 180Hz, third harmonics of fundamentals above 60Hz are attenuated by the low pass acoustic filters formed by the folds and front chamber.
To me, this makes a very good pairing of technologies. I think push-pull drive is ideally suited for basshorns. Some have said basshorns don't need it, or that it is better suited for direct radiators. I think push-pull drive is perfectly suited to folded basshorns. Push-pull works best at low frequencies, where summing is good and the cancellation of harmonics is best. Basshorns are acoustically small, so they start to lose their ability to load the woofer at the lowest frequencies. They can use the extra help down low. This makes the two technologies ideally suited for one another. Basshorns and push-pull drive work very well together.
I wouldn't do it any other way. Can't see why anyone else would either. Can anyone give me one good reason not to use push-pull drive in a folded basshorn?
Post by: Mike {AB} Butler on November 06, 2007, 04:41:17 PM
| Wayne Parham wrote on Tue, 06 November 2007 15:16 |
Even with just the 25 watt chart, we can clearly see a difference in the LABhorn and the 12Pi basshorn subwoofer. Where the distortion rises below 35Hz in the LABhorn, it rises much more slowly in the 12Pi. The same distortion you're getting from LABhorns at 25 watts, you don't see in the 12Pi until it reaches 1600 watts. That's pretty significant, don't you agree? |
Not really, as the horn probably sports better distortion figures than the LAB 12 driver that get used in it..
| Wayne Parham wrote on Tue, 06 November 2007 15:16 |
I wouldn't do it any other way. Can't see why anyone else would either. Can anyone give me one good reason not to use push-pull drive in a folded basshorn? |
I am thinking at this moment, the line from the Shakespeare play Hamlet, where the Queen says "methinks the lady doth protest too much.." I think you are pushing this waayy too hard. Why not spend your time building and perfecting these - if they are as good as you say they are; the marketplace will be your judge. Getting into a debate with Mr. Danley isn't doing much to get you the renown for your hard earned efforts thus far. Maybe it would be time to consider channeling this discussion into an action plan.. to build and prove your theories on some other platform, such as smaller boxes, which are desperately needed for many of us that don't have the space that a LAB sub or 12 pi take up.
Really. See if you could come up with a push-pull design that would be a fraction the weight, size, and still have the incredible power handling.. and go to at least 40 hz with solid, high level SPL. THAT would get everyone to sit up and notice, IMO..
Respectfully,
Post by: Wayne Parham on November 06, 2007, 06:14:15 PM
| Mike {AB} Butler wrote on Tue, 06 November 2007 15:41 |
See if you could come up with a push-pull design that would be a fraction the weight, size, and still have the incredible power handling.. and go to at least 40 hz with solid, high level SPL. |
We're working on a smaller version. I think it will have some trade-offs, but we're working on ways to minimize that. The current model is fine for people with large trucks that have ramps, but a smaller version would be nice for people that don't.
Post by: Grant Rider on November 06, 2007, 06:56:45 PM
Post by: Pascal Pincosy on November 06, 2007, 07:14:30 PM
Post by: Mac Kerr on November 06, 2007, 07:17:26 PM
Mac
Post by: Grant Rider on November 06, 2007, 09:31:56 PM
Post by: Tom Danley on November 06, 2007, 10:30:44 PM
I have saw the video of Topsy once and I suppose reading this thread may feel a little like that, hopefully without all the smoke..
On the other hand, perhaps you were suggesting that all this is an effort to put out the flame of “push pull”?
You reference it twice anyway.
Here is the thing, you can’t make outrageous claims with out overwhelming evidence and be taken seriously scientifically.
To find how much difference really makes you need to compare results “with and without” where being “push pull” was the ONLY thing that was different.
Keep in mind too that the driver is not what most people would have thought to use in a horn at the time either but that drivers parameters with the right front and rear volumes and horn produces very low distortion anyway.
Comparing to other horn systems using other drivers isn’t telling you anything about push pull.
Unlike Topsy’s days, back at the frontiers of high speed elephant BBQ, the idea of push pull is neither new or untried.
Some people have used it, conceptually it sounds like a good idea so it is good marketing..
Loudspeaker drivers are simply not so chronically flawed that push pull performs some miracle over conventional mounting and Wayne’s reported level of improvement (reducing all harmonic distortion components, not just the second) does not reflect the magnitude of what others have found or the math that describes the situation..
You can probably understand why I am skeptical and suggesting that he actually compare an identical horn with and with out push pull mounting as a way of determining just how big the effect is. What he has is a really good horn driver for that frequency range and horn parameters that makes very low distortion anyway.
Best,
Tom
Post by: Al Limberg on November 06, 2007, 10:36:45 PM
?;o)
Al
Post by: Grant Rider on November 06, 2007, 11:00:51 PM
Post by: Mac Kerr on November 06, 2007, 11:05:56 PM
| Grant Rider wrote on Tue, 06 November 2007 23:00 |
I missed Tom's explaination why the labsub generates the same amount of distortion at only 25 watts that a 12pi makes at 1600 watts. If not push/pull, then why? |
I know everyone is tired of this discussion, feel free to continue it via e-mail.
Mac