ProSoundWeb Community
Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB: The Classic Live Audio Board => Topic started by: Jim McKeveny on December 02, 2015, 07:51:11 AM
-
Lots of research and effort goes into the design of cones & drivers & dsp correction & amplification to produce nice spec'ing pro loudspeakers, but then we clamp reflective 60% open-area (i.e. 40% blockage) metal grilles on everything. I imagine these cause measureable response aberrations.
Back in the audiophile era, FR was often displayed grilles-on and grilles-off. Is there a manufacturers standard methodology when speakers are on the measurement turntable?
-
Lots of research and effort goes into the design of cones & drivers & dsp correction & amplification to produce nice spec'ing pro loudspeakers, but then we clamp reflective 60% open-area (i.e. 40% blockage) metal grilles on everything. I imagine these cause measureable response aberrations.
Back in the audiophile era, FR was often displayed grilles-on and grilles-off. Is there a manufacturers standard methodology when speakers are on the measurement turntable?
Jim, Who cares ?
The measurements better be as sold, as intended to be used. In other words, grills on. I don't really care what they will do hanging upside down, grills off, in a nudist park. That's not how they are usually used.
Audiophool and it's wizardry have very little correlation to live sound.
Chris
-
Yes, the grills do cause a number of different issues.
Part of it is a loss of HF-due to the direct blockage.
Another is the reflections off of the back of the grill-back into the speaker-and then causing combfiltering-due to the multiple arrivals.
Hopefully the spec sheet measurements are made with the grills on.
I was at one shootout a number of years ago and the other manufacturer actually took of the grills onsite to get more HF out of them.
That is not how they would be installed-but that is how they demoed them. Not exactly the same thing
-
Good timing. I just took the grills off my SH96HO's. Like an hour ago. Been meaning to do that for a while. Next shows on Friday and I'm expecting more hi end. I think they look better too. :)
-
I don't really care what they will do hanging upside down, grills off, in a nudist park.
I'd like to know what speakers do in a nudist park. Do they need to shed their grills too?
-
Good timing. I just took the grills off my SH96HO's. Like an hour ago. Been meaning to do that for a while. Next shows on Friday and I'm expecting more hi end. I think they look better too. :)
When I was kid we used to take the air cleaner off our car engine to make it faster...
JR
-
When I was kid we used to take the air cleaner off our car engine to make it faster...
JR
I thought it was more like the Harley-Davidson crowd immediately taking off the mufflers and changing the exhaust pipes . . . .
-
Good timing. I just took the grills off my SH96HO's. Like an hour ago. . I think they look better too. :)
You are not the first one to think so----------
-
When I was kid we used to take the air cleaner off our car engine to make it faster...
JR
But did it sound better? :)
-
You are not the first one to think so----------
Look even better if they let me paint them red or orange.
-
I thought it was more like the Harley-Davidson crowd immediately taking off the mufflers and changing the exhaust pipes . . . .
On many carbed cars of the 70's you could also flip the lid. Pull the vac. hose off the ER valve and stick a golf tee in. Crank up the timing a bit and put some bigger jets/metering rods in and you could really wake up a smog motor.
Sent from my SM-T800 using Tapatalk
-
Or you could remove the valve on a small block Chevy and block it with a plate.
I think I'll pull the grills off of my cabinets. That way the crowd will have a target for throwing shit at, it will make it easier to punch holes in the cones while moving them, and if I still owned a cat it would make it much easier for it to piss on them.
-
I think I'll pull the grills off of my cabinets. That way the crowd will have a target for throwing shit at, it will make it easier to punch holes in the cones while moving them, and if I still owned a cat it would make it much easier for it to piss on them.
Of course some speakers are easier to tear up with the grills removed than others--- ;) ;)
In some cabinet the drivers are not easily accessible and are more protected.
-
Or you could remove the valve on a small block Chevy and block it with a plate.
I think I'll pull the grills off of my cabinets. That way the crowd will have a target for throwing shit at, it will make it easier to punch holes in the cones while moving them, and if I still owned a cat it would make it much easier for it to piss on them.
Good points and if there was any chance of those things happening I wouldn't take the grills off either.
But mine are permanently flown and not in a bar.
-
Look even better if they let me paint them red or orange.
That's a matter of opinion John ;-)
I see some speaker grills that are honeycomb shaped holes and look like they provide the best open ratio.
-
Good timing. I just took the grills off my SH96HO's. Like an hour ago. Been meaning to do that for a while. Next shows on Friday and I'm expecting more hi end. I think they look better too. :)
If I did that to mine, I would have birds nesting in them. Then PETA on me for when the birds died after they were fired up.
-
I see some speaker grills that are honeycomb shaped holes and look like they provide the best open ratio.
I thought that too... Until I tried it out on CAD...
(http://stevesmithphoto.webs.com/grill.jpg)
This is with a 6mm wide aperture and 2mm of material between apertures.
If I offset the apertures out by 0.5mm keeping the spacing the same (increasing the aperture width to 7mm and reducing the solid material to 1mm wide) I get 75.56% for both.
Steve.
-
I thought that too... Until I tried it out on CAD...
(http://stevesmithphoto.webs.com/grill.jpg)
This is with a 6mm wide aperture and 2mm of material between apertures.
If I offset the apertures out by 0.5mm keeping the spacing the same (increasing the aperture width to 7mm and reducing the solid material to 1mm wide) I get 75.56% for both.
Steve.
Interesting point. I don't see many, if any, square hole speaker grills.
It is my understanding that with a honeycomb, the strength of the design allows for thinner material between holes.
That would allow more open space per square inch.
-
You could always adjust the flat space that is the problem to be less flat and make it a triangle. /\ So it will not bounce back as easily. That would be a very costly grill !
-
When I designed the speaker grille for the bottom of my drum tuner, protection and effectiveness were both important.
(http://compactdrums.com/wp-content/uploads/2015/09/20150927_115000.jpg)
At the frequencies I am dealing with the modest grille blockage was not an issue, and effectively transparent to the drumhead/speaker acoustic system. For my customer base (drummers) leaving the speakers exposed would be a bad idea.
JR
-
But did it sound better? :)
Actually there is an audible component to an unfettered air intake. Often drowned out by exhaust system noise but not always.
When I was a hot-rod kid, a friend of mine made his own DIY intake manifold to mount 3 one barrel carbs on his inline 6 (1953 Ford). That motor made more carb noise than exhaust rumble. Didn't go very fast compared to V8 motors of the time, but sounded pretty good with the intake in full honk. 8)
JR
-
Interesting point. I don't see many, if any, square hole speaker grills.
No. It's usually round or hexagonal. Obviously hexagonal has more open space than round, although you might be able to reduce the spacing between the apertures as it will be wider elsewhere.
I have some Peavey UL115 subs which have square perforated grills but I can't think of any others.
Steve.
-
Another is the reflections off of the back of the grill-back into the speaker-and then causing combfiltering-due to the multiple arrivals.
Besides throttling HF, reflections back-to and off-of baffle because of perforated/expanded metal could be seriously disruptive. I imagine JBL Vertec (+ others) leaving MF/HF uncovered is not just a styling exercise, but also good practice.
It would be nice if those mfrs. with serious measurement and preset research (L'Acoustics, JBL, D&B) could chime in here.
Otherwise, bring back grille cloth!
-
When I was kid we used to take the air cleaner off our car engine to make it faster...
If a choked airflow was a major limiting factor you did. You also introduced all kinds of airborne grit into the engine, causing premature valve & bore wear. Air filter assemblies are also a backfire flame arrestor ('cepting the really old oil-bath "cleaners" I imagine).
So overall a typically brilliant youthful idea...
-
Besides throttling HF, reflections back-to and off-of baffle because of perforated/expanded metal could be seriously disruptive. I imagine JBL Vertec (+ others) leaving MF/HF uncovered is not just a styling exercise, but also good practice.
It would be nice if those mfrs. with serious measurement and preset research (L'Acoustics, JBL, D&B) could chime in here.
Otherwise, bring back grille cloth!
As I understand it, when Danley did some tests regarding grill foam on the TH115 subs, they found it made a measurable difference.
-
As I understand it, when Danley did some tests regarding grill foam on the TH115 subs, they found it made a measurable difference.
It was the combination of the cloth and the metal grill that affected the LF response.
The cloth makes no difference on the full range products. The exit are is much larger.
But on the tapped horns, it did "choke off" the response.
But we need the grill for protection.
NOW-Let's look at the REALITY.
I don't have measurements to show-and can get some when I get back in the office-if I find some time.
Yes the HF response is reduced a little bit because of the open area of the grill.
But how MUCH is the question, and will the average person even notice?
Once you get a decent distance away-the air absorption is going to be the biggest issue-and a grill or not is simply not going to be heard.
Just like if I pee into a lake. Technically the lake level rises. But is it enough to be concerned with?
Sometimes people get "hung up" on things that don't make any real difference, yet let "the big issues" go right on through.
So let's go back to reality. Suppose the HF is reduced because of the grill. If you want that HF you will simply eq it as needed.
-
I have to think anything that disrupts the flow of air will make a measurable difference. but I would also have to believe that reputable manufacturers take that into consideration during the design and test phase. That's also my reason for not placing too much emphasis on grill appearance or design when making purchasing decisions.
EV used, and probably still uses, foam grill backing to their advantage, the Sx500+ being a prime example. That cabinet has a round piece of 1/4" foam directly over the middle of 15" driver. I owned 1/2 dozen of these at one time in my life, and thinking the cabinets would sound better with the foam removed I experimented on a pair of them. Having untouched cabinets to compare side by side opened my eyes, and the result of removing the foam did exactly what I thought it would. It opened up the midrange response, but to a point where mid range honk was introduced. I could almost EQ the cabinet back to the original sound with all of it's smooth response and glory, but close is not good enough, and the effort to EQ the cabinets far out weighed the benefits. Needless to say the foam was put back on to the grill and that experiment chalked up to experience.
-
\
Sometimes people get "hung up" on things that don't make any real difference, yet let "the big issues" go right on through.
So let's go back to reality. Suppose the HF is reduced because of the grill. If you want that HF you will simply eq it as needed.
The concern about the grill is minor when you end up forced to have so called "blow through" hung in front of your speaker system!
-
If a choked airflow was a major limiting factor you did. You also introduced all kinds of airborne grit into the engine, causing premature valve & bore wear. Air filter assemblies are also a backfire flame arrestor ('cepting the really old oil-bath "cleaners" I imagine).
So overall a typically brilliant youthful idea...
Back in those days I would break my engines well before they came close to wearing out, and they didn't start out new, just put the cam and heads on a different (used) short block and we're ready to rumble.
One night I experimented with connecting the heater fresh air intake tube, to the air filter housing intake. So I had cold air running direct into the top of the carb. Motor was running really good that night until I threw a rod, cutting my oil pan in half... :'(
I do not advocate running without an air filter and these days run K&N low resistance air filters. 8) I even used an air filter in front of the supercharger I put on one car.
JR
PS: For live sound use I'm inclined to trust the manufacturer to design for use with the grills in place. If you think you're smarter than the manufacturer, you probably aren't.
-
Lots of research and effort goes into the design of cones & drivers & dsp correction & amplification to produce nice spec'ing pro loudspeakers, but then we clamp reflective 60% open-area (i.e. 40% blockage) metal grilles on everything. I imagine these cause measureable response aberrations.
Surprisingly, well not for acoustics, the percent open area is not that significant. What is important is the size of the web material between the openings. For the quick and dirty have a look at examples 1 and 2 on pdf pages 20 and 21 of http://www.iperf.org/files/1313/9265/8912/The_Acoustical_Uses_for_Perforated_Metals_Handbook.pdf (http://www.iperf.org/files/1313/9265/8912/The_Acoustical_Uses_for_Perforated_Metals_Handbook.pdf). The metal with 53% open area increase over the first example has 2 dB greater attenuation than the smaller percentage open area! Of course the rest of the document goes into more detail.
Andre
-
Is that a bug or a feature ? http://i.ebayimg.com/images/i/151608387622-0-1/s-l1000.jpg ;D
-
Is that a bug or a feature ? http://i.ebayimg.com/images/i/151608387622-0-1/s-l1000.jpg ;D
Feature.
-
Is that a bug or a feature ? http://i.ebayimg.com/images/i/151608387622-0-1/s-l1000.jpg ;D
Near as i recall, you stick a 2441 or 2445 on it, as a wedge, you can use it to clear the stage.
Ungodly loud - if you so desire.
Great way to poke a hole in something with a bit of 4K ;D ;D
-
If you think you're smarter than the manufacturer, you probably aren't.
Agreed.
But the lack of transparency (Ha!) from manufacturers is of concern. A percent here, a percent there, soon we are talking about real sound and money.
As engineering-aware end users in an engineering realm should we not ask these questions?
-
That particular potato masher lens was for a one inch driver ala 2421. They were popular back in the day for use in wedges next to a 12. Made it damned hard to have a stable vocal mix when the singer moved the mic even a few inches. For the yonger set who may be scratching their heads muttering WTF, this is a conical exponential horn with an "acoustic lens". This predates the entire constant directivity design and the lens was installed at the mouth of the horn to make the pattern wider than the horn would have been capable of delivering otherwise. THis is a constructive ( sort of ) use of the phenomena under discussion in the thread.
Near as i recall, you stick a 2441 or 2445 on it, as a wedge, you can use it to clear the stage.
Ungodly loud - if you so desire.
Great way to poke a hole in something with a bit of 4K ;D ;D
-
Near as i recall, you stick a 2441 or 2445 on it, as a wedge, you can use it to clear the stage.
Near as I recall it was a 1 incher.
-
Made it damned hard to have a stable vocal mix when the singer moved the mic even a few inches.
Which supports the perf. metal/wickedly peaky thingy I OP'd.
I am guess that w/o mfr input this thread will dissolve into the anectdotal..
-
I am guess that w/o mfr input this thread will dissolve into the anectdotal..
Have a look at my first post in this thread. Nothing anecdotal. Research by then member of Bolt, Beranek and Newmann
-
Not sure the merits and demerits of perforated plate acoustic lenses designed in the 50s for home stereos to over come the short comings of short conical horns and misapplied for stage monitors twenty years later makes the thread about perforated metal speaker grilles without value.
Which supports the perf. metal/wickedly peaky thingy I OP'd.
I am guess that w/o mfr input this thread will dissolve into the anectdotal..
-
As a design factor I would SWAG that the effect differs depending on whether the grill is in the region where the driver does work on the air or when the wave is propagating which would depend on placement of the driver and frequency.
After all sound is a compressional wave not a transverse wave.
Sent from my XT1254 using Tapatalk
-
Agreed.
But the lack of transparency (Ha!) from manufacturers is of concern. A percent here, a percent there, soon we are talking about real sound and money.
As engineering-aware end users in an engineering realm should we not ask these questions?
We should ask these questions in the format being used, that of a discussion. If I used JBL as an example, then who among us has the product knowledge and test equipment available to dispute their design.
-
I fired up mt SH96HO's without the grills and having no test gear used my ears. Definitely brighter. I wound up turning the tops down 1 db and changing a 6.5k -6 db cut to a 6.2k -9 db cut. I used Alan Parsons Turn of a Friendly card as my test music as I've noticed sibilance in the vocals. It really came out without the grills.
I'll see how the show goes tonight.
-
But did it sound better? :)
It probably did, -you would be surprised how much noise comes out of an engine's intake!
-
I thought the show sounded very good tonight. Didn't have any sibilance and wound up going back to my original settings. I thought that there was a touch more clarity especially in the vocals. Nothing major but I'm leaving the grills off.
-
I did a show in a nudist park once. Picture a room full of ugly naked people dancing to 60's and 70's Rock and yes, I did leave my grills and clothes on.
-
I did a show in a nudist park once. Picture a room full of ugly naked people dancing to 60's and 70's Rock and yes, I did leave my grills and clothes on.
I'm sure the other people appreciated that kind gesture :)
-
It probably did, -you would be surprised how much noise comes out of an engine's intake!
True! On the track, we could easily tell the Vtec Honda engines by the sound of the (non stock)intake when the cam cam on.
Much more noise than you would expect and gave credit to the quiet design of the stock intake systems.
Missed that with my turbo, non Vtec engine. Nice power but less noise :)
-
True! On the track, we could easily tell the Vtec Honda engines by the sound of the (non stock)intake when the cam cam on.
Much more noise than you would expect and gave credit to the quiet design of the stock intake systems.
Missed that with my turbo, non Vtec engine. Nice power but less noise :)
OK here is a picture of my actual air filter from back in the day... It let my 4 barrel breath without letting small animals into the intake system.
Can't say that I heard much carb sound over the exhaust note that tended to be quite a bit louder.
JR
-
When I was kid we used to take the air cleaner off our car engine to make it faster...
JR
and for the quadrajet(bawoooooooom) carb sound.
http://www.youtube.com/watch?v=IjL9hmdbqj4
-
OK here is a picture of my actual air filter from back in the day... It let my 4 barrel breath without letting small animals into the intake system.
Can't say that I heard much carb sound over the exhaust note that tended to be quite a bit louder.
JR
i dont use an air filter, i use a "carburator" filter. it filters the carburator out of the engine , it keeps the carburator from going into the engine.
-
and for the quadrajet(bawoooooooom) carb sound.
http://www.youtube.com/watch?v=IjL9hmdbqj4
Actually a decent sized Holley (650 CFM IIRC) that I bought off a junkyard 396 ci chevy...
The quadrajet was a rochester carb.
JR
-
No. It's usually round or hexagonal. Obviously hexagonal has more open space than round, although you might be able to reduce the spacing between the apertures as it will be wider elsewhere.
I have some Peavey UL115 subs which have square perforated grills but I can't think of any others.
Steve.
JBL SR4700 series had square perforated grills.
-
When I was kid we used to take the air cleaner off our car engine to make it faster...
JR
I can still hear the deep moan of my parents '58 Chevy, 348 cid, power glide with the air cleaner in the trunk! My Dad would have kicked my ass if he'd known. :-)
-
I can still hear the deep moan of my parents '58 Chevy, 348 cid, power glide with the air cleaner in the trunk! My Dad would have kicked my ass if he'd known. :-)
The day I bought home my 71 Trans Am (455HO, 4spd) in 1976 or 77, I "let" Dad take it for a spin. After parking it, he says "You know, if that thing wasn't so bloody loud, I'd like to take it to work, and show off to the kids."
He is an interesting man, my Father. He's pushing 80 now, and still likes to "play"
everyone should be so lucky.
Chris.
-
I can still hear the deep moan of my parents '58 Chevy, 348 cid, power glide with the air cleaner in the trunk! My Dad would have kicked my ass if he'd known. :-)
(http://www.johnhroberts.com/timecard.jpg)
Back in the '70s I was visiting friends who were racing their cars. I was driving my street stock Barracuda (small v8 2 barrel). I paid for a pit pass so i could hang out with my friends in the pit, and they said I should race my car. I borrowed a helmet and put my air cleaners in the trunk..... I won*** H-Stock Automatic. 8)
JR
*** only reason I won was because all the go fast boys, were bracket racing for more money. I got a cheap trophy and actually turned in a faster time than F stock. :-[
-
Of course the BEST way is to no speculate, but actually MEASURE-WOW-what a concept :)
I know some people don't like to measure and would rather speculate and "model", but I am old fashioned and like to actually measure and see what is happening in the REAL world.
So I was doing some measurement today and thought I would give it a shot.
This is a kinda large horn (45" x24") with a 1.4" driver.
As you can see, the grill both CUTS AND BOOSTS the high end. It DEPENDS on what freq you are talking about.
Here is a screen shot, On axis about 2M away, with 2 seconds of averaging and a pretty narrow vertical window.
The PINK is without the grill and the GREEN is with the grill.
The grill is about 60% open and no backing cloth.
I will let others decide if the 0.1dB is worth consideration----
And before anybody asks-NO I did not do any off axis measurements.
I have a lot to do to finish up the year and just wiggled this one test in-since I was setup.
-
Of course the BEST way is to no speculate, but actually MEASURE-WOW-what a concept :)
I know some people don't like to measure and would rather speculate and "model", but I am old fashioned and like to actually measure and see what is happening in the REAL world.
So I was doing some measurement today and thought I would give it a shot.
This is a kinda large horn (45" x24") with a 1.4" driver.
As you can see, the grill both CUTS AND BOOSTS the high end. It DEPENDS on what freq you are talking about.
Here is a screen shot, On axis about 2M away, with 2 seconds of averaging and a pretty narrow vertical window.
The PINK is without the grill and the GREEN is with the grill.
The grill is about 60% open and no backing cloth.
I will let others decide if the 0.1dB is worth consideration----
And before anybody asks-NO I did not do any off axis measurements.
I have a lot to do to finish up the year and just wiggled this one test in-since I was setup.
Winner Winner Chicken Dinner!!
Thanks Ivan!
-
Of course the BEST way is to no speculate, but actually MEASURE-WOW-what a concept :)
I know some people don't like to measure and would rather speculate and "model", but I am old fashioned and like to actually measure and see what is happening in the REAL world.
So I was doing some measurement today and thought I would give it a shot.
This is a kinda large horn (45" x24") with a 1.4" driver.
As you can see, the grill both CUTS AND BOOSTS the high end. It DEPENDS on what freq you are talking about.
Here is a screen shot, On axis about 2M away, with 2 seconds of averaging and a pretty narrow vertical window.
The PINK is without the grill and the GREEN is with the grill.
The grill is about 60% open and no backing cloth.
I will let others decide if the 0.1dB is worth consideration----
And before anybody asks-NO I did not do any off axis measurements.
I have a lot to do to finish up the year and just wiggled this one test in-since I was setup.
There you go confusing the issue with FACTS.
JR
-
Thanks for posting that Ivan. Wish I had the gear to do my own testing.
But it does look nicer :)
-
Thanks for posting that Ivan. Wish I had the gear to do my own testing.
But it does look nicer :)
Yes you "could argue" that the grill response is "smoother".
But would challenge ANYBODY to do a blind test and pick out 0.1dB differences-especially over the limited range that they are affecting.
Now I will admit that the "total experience" with the grill on may be different than what I measured.
I did not have reflections getting into the measurement-and as you move off axis the "apparent open area" is less than on axis.
You can see this by looking at a grill with holes in it-as you look at it from an angle, the holes get more oval and the total open area is less.
So more reduction is possible-so the reflections are going to have less HF than without the grill.
Of course this will "depend" on the particular situation.
I doubt I will have time (I have a VERY limited amount of time left in the year-we are talking about just a few hours) , but if I get a chance I will grab a quick off axis measurement and see how it is affected.
Measurements win every time over speculation or modeling. But not everybody believes that. They would much rather play on the computer than get out in the real world and SEE what is happening--------- Oh well.
-
It might be worth making more measurements if the differences were larger (audibly significant) and people didn't have EQ.
That difference is less than how flat some EQs aren't when zero'd.
JR
-
JR -
"That difference is less than how flat some EQs aren't when zero'd."
Can I make up some t-shirts, please... hehe
-Tim T
-
I'd be curious to see the phase trace comparison of these two measurements.
Of course the BEST way is to no speculate, but actually MEASURE-WOW-what a concept :)
-
I'd be curious to see the phase trace comparison of these two measurements.
Sorry, but I didn't save the file.
I was working on other things, so just did a quick screen capture.