Post by: Sam Jayaraj on May 14, 2005, 02:37:38 AM
Now I want to built 4 or 6 Nos. of roadworthy subs. Which is better? Labsubs or Tuba36Slim for maximum spl and extension to atleast 32Hz?
Thanks in advance,
Post by: Matt Loretitsch on May 14, 2005, 09:33:10 AM
The lab subs are tougher to build and heavier for a reason. Higher ouput, lower extension. Both of them need to be in groups of two or more to perform. The LAB is more proven by years of experience currently.
If you decide on the 36slims make sure you use the Magnum 15LF Bill recommends. It's well made and will give you good output with 1.5kw to each driver.
For a small beans guy like myself the 36S is a good box. I have to deal with stairs several times a year and the labs would be killer to move up a flight or two.
-Matt
Post by: Michael_Elliston¶ on May 15, 2005, 12:21:54 AM
http://homepages.paradise.net.nz/sbk1/ssi.htm
Post by: Sam Jayaraj on May 16, 2005, 06:47:25 AM
I built the Tuba24; this morning I completed one box and loaded it with an HL10A driver. Tested with some music. It does not go deep (only one box, as of now, and three more are in the course of completion), but it is really impressive for its size. I guess the Tuba36 must have the same family sound.
One more question: Apart from maximum SPL, which of the two, LabSubs or Tuba36Slim will have a longer throw?
Thanks,
Post by: David Trotter on May 16, 2005, 07:02:06 AM
I was planning on building a few Tuba 24's too for smaller things. Few questions:
You recon they outperform a simmilar sized 15" reflex box?
How low do they actually go and how clean is the sound?
How hard are they to put together?
How much power do they realistically handle (i was thinking 500w)?
Let us know how all 4 sound eh!?
ta
-dave
Post by: cmqt9 on May 16, 2005, 12:04:49 PM
The graphs I've seen of the T36 slim show half-space 1m/1w response. Graphs I've seen of the Lab also show half-space 1m/1w response, and they aren't a whole lot different. McBean sims of the two also show the same thing. The two designs are definetely different, but the jury is still out on which, if either, is better.
Post by: Mac Kerr on May 16, 2005, 01:41:05 PM
| cred_audio wrote on Mon, 16 May 2005 06:47 |
One more question: Apart from maximum SPL, which of the two, LabSubs or Tuba36Slim will have a longer throw? Thanks |
| Dave Gunness wrote on the EAW site |
A "long throw" speaker is normally considered to be a high-directivity speaker. Vertically, because it projects a tight beam, you're able to "throw" the sound over the heads of the nearest listeners without killing them with SPL. Horizontally, it sends less energy into the sidewalls of the room - so the reverb picks up more slowly as you walk toward the back. When it comes to floor-stacked subs, neither of these effects apply. All of the listeners are in the direct path of the subs, so there is no throwing it over their heads. Also, all subs have wide patterns, and nearly all rooms have relatively long reverb times at low frequencies - so the effect of low frequency directivity on the distribution of reverb in a room is usually insignificant. What is important is the area of the wavefront where it exits the box. In order to squeeze 100 acoustic Watts out of an 18-inch woofer, the sound pressure has to be extremely high at the surface of the woofer. If the same 100 acoustic Watts comes through a 3-foot by 3-foot horn mouth, the sound pressure will be much, much lower at the mouth (nearly 10 dB less). A hundred Watts is a hundred Watts, so at 50 feet, both systems will produce the same SPL. The difference then, is that for a given SPL at distance, the SPL down close to the speakers is much lower for the horn than it is for the direct radiator. That means the horn produces less SPL variation from near to far - than the direct radiator does. Some people would call that "throw". Incidentally, this form of "throw" works the same indoors as it does outdoors. David Gunness |
Mac
Post by: bgavin (Bruce Gavin) on May 17, 2005, 07:35:24 AM
| cred_audio wrote on Mon, 16 May 2005 03:47 |
8)I built the Tuba24; this morning I completed one box and loaded it with an HL10A driver. Tested with some music. It does not go deep |
The Tuba24 is not intended for music (deep), but for pro-sound reinforcment (loud).
The horn length of the Tuba24 is approximately 5 feet, making the horn cutoff point (Fc) at 56 Hz. Below this, the box operates as a bandpass device. Mouth area is 3.67 square feet, which only provides full horn loading to 62 Hz in half-space (on the ground). A pair of Tuba24 on the ground is sufficient mouth area to reach Fc with full horn loading.
More than a pair of Tuba24 will provide a larger mouth area, but this is pointless with an Fc of 56Hz. The horn won't go lower than this, no matter how much the mouth area is increased. It will get louder, though.
The Tuba36 Slim at 7.5 feet has an Fc of 37 Hz. The horizontal baffle model offers higher SPL, but does not extend as deep as does the vertical baffle Slim. Neither has the low extension of the LAB sub, with its longer air column. All require suffcient mouth area to achieve Fc with full loading. At 37 Hz, this is 37 square feet in half-space.
Post by: Elliot Thompson on May 17, 2005, 08:00:16 AM
| bgavin wrote on Tue, 17 May 2005 12:35 |
The Tuba36 Slim at 7.5 feet....... |
Thats intresting. I assumed it was more than 7.5 feet.
Thats .5 more of a Scoop. JBL's Scoop. Or are you refering
to internal chamber the 15 sits in?
Best Regards,
Post by: Tom Danley on May 17, 2005, 01:26:47 PM
Fortunately, one does not have to depend on subjectivity to evaluate a design if one has sufficient modeling capacity. It is cool that there are free ware horn simulators out now but they do not tell all.
I normally consider a few additional things aside from 2.83 Volt sensitivity when I design something as I did with the LAB sub.
For example, how loud (what percentage of max power) can it go at the point of reaching Xmax? What is the ratio of power in to power dissipated in the VC?
I guess the point is the LAB sub was also designed to play very loudly and cleanly, while the T36 has not been tested in a side by side, some others have been and measured at the same time. If you want more to base your opinion of the LAB sub on, look up the sub shoot out that took place in Michigan.
You mention the drivers, it was necessary to get this level of performance to have a specific driver made to specifications. Yes there were some with a glue problem in the beginning but failures now only happen well past the power levels I suggested and these have proven (by track record) to be very beefy.
So far as an advantage to the LAB sub over the T36, it would mainly be that the LAB sub can go much louder down low before reaching the limits of the driver.
It was built for a different purpose (large scale Live sound) to be used in groups of two or more and in a size and low cutoff picked by the group. Part of the intention was to give (for free) the DIY’r a design for something really powerful that they wouldn’t normally have access to. The thought of a home built LAB’s being compared to any of the Big companies products was also part of the fun you see.
Cheers,
Tom Danley
Post by: Michael_Elliston¶ on May 17, 2005, 04:29:18 PM
Considering the labhorn held its own against the best of the world in this shootout... Check the revised impulse responses and see their shape-interesting.
http://www.geocities.com/xobt/index2.html
Post by: bgavin (Bruce Gavin) on May 17, 2005, 08:53:33 PM
| Elliot Thompson wrote on Tue, 17 May 2005 05:00 |
Thats intresting. I assumed it was more than 7.5 feet. Thats .5 more of a Scoop. JBL's Scoop. Or are you refering to internal chamber the 15 sits in? |
7.5 feet is the horn length.
I bought the plans to build (3) of the Tuba36 Slim, using 15" drivers I have on hand. Even then, (3) are only enough mouth area (half-space) for full loading to 55 Hz.
The LAB are bigger 'n badder, no doubt about it. But I don't have need for that much Badness, nor response below 41 Hz. Portability is more of a concern for me, and even T36 Slims are a lot to move around.
Post by: Sam Jayaraj on May 18, 2005, 03:05:32 AM
It is great to see you respond to my queries. Since you are the designer and have also studied the results of on-field tests of the LabSub, which of the 3 versions would you recommend for prolonged and continued (ab)use in live concerts?
A member wrote that the Tuba36Slim goes deeper when fewer boxes are used. What number of Tuba36Slims vs. LabSubs constitute the breakeven point at which the Tubas advantage disappears?
Post by: cmqt9 on May 18, 2005, 07:07:39 AM
http://www.eaw.com/images/products/ClubSpectrums.jpg
In the original Tuba 24 article in Audioxpress magazine Bill explained how he took RTAs at a large concert venue for two years and found that flat response below 50 Hz was just not necessary, although extension at a lower SPL to 30 Hz was. Based on that data he came up with the stepped response of the Tuba design. This information now on the EAW site is saying pretty much the same thing. Based on the EAW chart, which is very close to that Fitzmaurice published, it looks like flat to 41 Hz is more than enough. I'm leaning towards the Tuba 30, its 45 Hz fc should do. Though if that EAW RTA is dead on it could be that a wall of T24s is actually the best configuration.
I believe the pathway of the t36 is 8.5 feet measured down the centerine.
Post by: bgavin (Bruce Gavin) on May 18, 2005, 09:18:11 AM
The live sound RTA analysis puzzles me for a couple of reasons. The lack of bass program below 60 Hz could be from several causes:
1) Bass player doesn't play down low
2) Cabs don't produce much below 60 Hz
3) Power amp 50 Hz filters in place
As a long time musician and bassist, I suspect #1 and #2 are big factors. When I watch the young bands, most of them play 4-string basses from low A (55 Hz) and higher. The exception is my daughter's bassist (www.aroarah.com) who routinely drop-tunes down to C# (34.6 Hz) and uses those notes. There is a huge difference in bottom between her band and the typical bass-strumming punk band.
Many bands insist on micing their bass cabs "for tone" instead of using a DI. The big Ampeg (sealed) cabs, Eden XLT, etc, all have significantly reduced output below 60 Hz. Even with full PA support, the bottom will be absent.
I have not done the layout yet for my herd of Tuba36 Slim. Bill states the horn length is 7.5 feet, so I take him at face value on this. I prefer the smaller Tuba30, but would then have to purchase drivers, whereas I already have several 15" on hand.
The Tuba36 responds to a horizontal baffle for higher SPL, or vertical baffle (bandpass) for lower extension. Bill says this does not apply to the Tuba30, and to stick with the vertical arrangement and 12" driver.
Post by: fernand on May 18, 2005, 11:06:33 AM
I agree with you mostly.
I think that there might be a chicken and egg problem too.
As the majority of PA systems don't go much below 50 Hz (even if they can go lower, they prefer not to as it eats quite some PA capacity), it is normal that RTA will show up lower levels below 50 Hz.
Secondly, I think that the RTA measures are averaged over some time. Because bass is often part of the rhythm with peaks and silences, I think we should consider peak measurements.
I'm having a four string and very often, I drop tune.
I'm having the following Ampeg bass reflex speakers:
SVT-410 HLF - F3 48 Hz - F10 28 Hz
PR-410 HLF - F3 33 Hz - F10 29 Hz
I can tell you that the PR sounds significantly better at the low end. Problem with both cabinets is that when I crank a little bit the low end, both start farting out quite quickly. Therefore I am looking to improve my low end capacity.
As you implied, most people don't know the joy of the low end, and I guess that in a lot of places, it is not appreciated as it might have a physical impact on all sort of things that start rattling.
I do agree that the fundamentals below 60 Hz for most instruments can be at a lower level as Bill claims.
I can live with a cabinet that below 60 Hz has a lower efficiency because I know I can correct it with EQ.
Without EQ however, I would have only bass extension in homeopathic doses (-10 dB from the source, - 10 dB from the cabinet).
Post by: jeffhtg (Jeff Kenney) on May 18, 2005, 03:03:51 PM
Post by: bgavin (Bruce Gavin) on May 18, 2005, 05:21:32 PM
The above is pure speculation because I have no positive knowledge. Most of the commercial cabs are wildly optimistic on their claimed specs, especially F3. It wouldn't surprise me to find a no-bottom RTA measurement resulting from micing a no-bottom cabinet.
I've never had an Ampeg cab on the test bench, but I spent quite a bit of time with an Eden D410XLT, and it is a gutless wonder in the bottom octave. Any cab of this general size that claims an efficiency of 105 SPL at 1w/1m, has to be gutless on the bottom (or measured at the tweeter and 1 KHz). High efficiency drivers require a very large cabinet volume to get down low.
I have no SMAART experience, but it would be interesting to see what an RTA of the *signal* looks like, when compared to what is being produced at the drivers, by that signal. If they match, there is no low program material being produced. If they don't match, the drivers are not reproducing the low signal.
Again, all the above is moot. Since I haven't done the RTA measurements, I can only take Bill and EAW at their word.
Post by: Elliot Thompson on May 18, 2005, 10:39:21 PM
| bgavin wrote on Wed, 18 May 2005 01:53 |
7.5 feet is the horn length. I bought the plans to build (3) of the Tuba36 Slim, using 15" drivers I have on hand. Even then, (3) are only enough mouth area (half-space) for full loading to 55 Hz. The LAB are bigger 'n badder, no doubt about it. But I don't have need for that much Badness, nor response below 41 Hz. Portability is more of a concern for me, and even T36 Slims are a lot to move around. |
Okay. Thanks for providing your analysis.
Best Regards,
Post by: fernand on May 19, 2005, 01:15:09 AM
I certainly take the specs of bass cabs with a pinch of salt, but we selected those Ampeg cabs based on numerous A/B tests we did ourselves. They have only a sensitivity of 96 and 98 dB.
But anyway, they bottom out quite quickly, so I come to the conclusion that a spec of a cab is useless if you have no information about real max performance.
I plan to build a bass horn by the end of the summer.
Once I have the cabs, I would like to perform a measurement campaign on the Ampegs and the horn. I'm a bit tired of the numerous performance claims while we almost never see real measurements. I don't pay attention anymore to my-simulation-is-better-than-yours discussions. Power compression can lead in the lower bass regions to more than 6 dB reduction, Xmax limitations, as on my Ampegs, reduce the maximum with probably more than 12 dB.
In that light, it might be interesting to start a thread that makes an inventory of used measuring tools and methods used by various users, along with an appreciation of cost, effort, limitations and results.
Once we have that, we could start another thread to define an easy and uniform PSW measurement method or procedure, along with the things we want to measure, for example:
Basic measurement: the SPL/freq graph classic at x meter in half space
Power measurement: ideally, I would like to see the maximum power SPL and its associated distortion (to detect Xmax problems), but maybe there is a way to make a curve that contains a Xmax and power limited SPL graph.
I'm sure, there might be other interesting measurements, such as pulse response and phase (at crossover), but I guess thats for later.
I noticed that the RTA measurement taken by Bill was not limited by the PA equipment, but it still might be useful to see peaks in stead of averages. Concerning the EAW graph, without background information on that graph, I would not base an opinion on that.
Post by: Craig Leerman on May 19, 2005, 02:20:03 AM
| Quote: |
The live sound RTA analysis puzzles me for a couple of reasons. The lack of bass program below 60 Hz could be from several causes: 1) Bass player doesn't play down low 2) Cabs don't produce much below 60 Hz 3) Power amp 50 Hz filters in place |
Another reason could be the style of music. Some live bands like Reggae, Dancehall, or Rap/Hip Hop are going to have way more bottom than say a Country or Pop act. If the live venue Bill measured mainly did mainstream acts like Pop, Rock, or Country, that would explain the lack of some bottom end.
In addition, acts with keyboard players or Synth players may generate more bottom end that a 4 or 5 string bass player will. I did sound for a Prog Rock band a few years ago that used a synth bass all night. 4 MT-4 Manifold quad 18s per side had a hard time keeping up with that guy! He would do sweeps down into the 20Hz region.
Last, I was thinking that if this was a place with a house engineer, that the FOH person themselves could be the cause of the lack of bass. I know a FOH engineer who doesn't like a lot of bass (He comes from a country and bluegrass backround). It could be that the FOH engineer simply didn't push the low end like many folks do. (right or wrong)
Either way, my vote is for a PA that can handle at least 40Hz before sloping off. I would rather have the bandwidth available and not use it, than be limited by the PA.
Craig
Post by: bgavin (Bruce Gavin) on May 19, 2005, 09:58:10 AM
IMO, where this theory falls flat is a Fender bass in the studio (DI) has far more low content than the same bass in a live situation (standalone or miced cab + PA cabs). The bass harmonics are unchanged between studio and stage, and only the reproducing medium is changed.
Degradation is cumulative between stages. If the electric bass is weak in the fundamental, reproducing this signal through a PA designed to be weak below 60 Hz compounds the problem. Micing a bottomless bass cabinet, then reproducing it through this bottomless PA seriously exacerbates the problem. RTA analysis done on this example shows no bass content, but does not say why. Failure of the reproducing chain is the cause, not lack of content.
Half-space measurements of the Tuba24, with its conical design and 56 Hz horn length, show significant roll off below 80 Hz. The Tuba24 meets its design goals, so I do not fault the line of thinking in this case. However, anybody expecting to realize a full 41 Hz out of this box will be disappointed.
Full horn loading to 41 Hz requires a minimum 6.88 foot hyperbolic horn, or longer exponential/conical type, and a mouth area of 30 square feet in half space. Measurements show exponential horns are useful down to about 125% of design Fc, and conical horns roll off even higher. Multiple LAB subs or multiple larger Tubas are required for sufficient mouth area and horn length to get down this low.
Due to the faceless nature of the internet, this post is not intended to be belligerent in any way. That said, I remain unconvinced as to "why" the RTA analysis shows little content below 60 Hz.
Post by: raj on May 20, 2005, 12:36:23 AM
In your post dt 17th instant you have written "The Tuba36 Slim at 7.5 feet has an Fc of 37 Hz."
I think you have posted the horn length of the Tuba 30 instead of the tuba 36 ,
after reading your post I had doubts of the length written by you and did the following measurements of the horn leanth my tuba 36 slim ,
Horn length inner side of the horn 9ft,
Horn length centre of the horn 9ft 10inches,
Horn length outer side of the horn 10ft 6inches,
I do not know how to measure a horn , I just took a nylon rope and spread it along the path and then measured the rope , I may be +/- 1 inch in my measurements , I hope I am right ??
Post by: Johan Rademakers on May 20, 2005, 10:21:01 AM
| Quote: |
Traditionally the path is measured down the center. You normally would start the measurement at the leading edge of the driver hole in plate 1. My estimate is about 8.5 feet, starting at the junctions of plate 1 and 2 to be conservative |
[ edit] Eeerrr...Seems you already knew
[/edit]Mvg Johan
Post by: [x] on May 21, 2005, 07:28:22 PM
Post by: [x] on May 21, 2005, 07:45:42 PM
Post by: peter.golde on May 21, 2005, 08:13:44 PM
What is the point of your post? Your failed attempts at horn design qualify you as an expert? Or is it your experience with your buddies Tuba24 that doesnt play as low as you would like. How many horn designs have you built and tested? How much experience do you have with horns in live sound apps?
Ask raj how he likes the Tuba36S. Ask anyone who built the Tuba24, and are using it for what it was designed for, if they are happy with it. The Tuba24 was designed for backline, low frequency for bass guitar in a two way bass guitar rig, using a Beta10. It was found to work well enough for use with the HL10a in higher power applications. Although the HL10a is not the best driver for the horn, Bill F. will be the first to tell you this. Eminence (according to Bill F.)is seriously looking at designing a new version of the HL10a for use specifically in the Tuba24 horn.
Post by: Dave Rickard on May 21, 2005, 11:54:28 PM
| BHFProfessional wrote on Sun, 22 May 2005 00:28 |
My own experience with the Crusher project taught me what the HL10 likes and doesn't like. |
Ummmm.....Please elaborate on your *experience* with the Crusher/HL10. As a student of science you know that hypotheses and simulations do not qualify as experience. Sawdust, trials, applications, and measurements do.
Dave
Post by: efreak on May 22, 2005, 02:17:05 AM
efreak@efreaked.com
Post by: cmqt9 on May 22, 2005, 08:52:27 AM
Well, I wouldn't go that far, but Rory, there is a lot more to being a professional than just calling yourself one. We've been anxiously awaiting the arrival of your promised designs for about a year now, and it somehow never happens. I could give some credence to your opinions if you'd ever built a single speaker, but so far as I can tell you never have. I'm not dismissive of your academic endeavors, but being a student doesn't make you a pro. I have my degree and I don't call myself a professional loudspeaker designer. You can assume that mantle after you've done the deed. Perhaps a change in your moniker to 'aspiring professional' would be more appropriate.
I have a Tuba 24 and can't fault it in any way, it does exactly what it's supposed to do. It's advertised as a cabinet for backline bass and small to medium venue PA and when so employed works as well or better than any other 8 cubic foot cabinet I've ever heard. That's quite a few cabs too, because while I may have an engineering degree I make far too much money as a working musician to take a cut in pay and do anything with it.
My experience with my own Tuba 24 aside I prefer Fitzmaurice's approach from an engineering standpoint because they are goal-specific designs. Will Labs outperfrom T30s and T36s? Yes, if you use enough of them and you require flat response below 35 Hz. Does live music program require flat response below 35 Hz? Mounting evidence from a number of sources indicate that the answer is decidedly no, so there is little point in hauling about cabinetry large enough to do so. Fitzmaurice used horn loading to get to a desired fc at a desired SPL and then from the same cabinet direct radiation to extend response below fc at reduced SPL, in so delivering a response curve actually required by the program material from the minimum cabinet volume and at the lowest possible cost. That was his goal and he achieved it. The Lab goal was flat to 22Hz or thereabouts and Tom achieved that. I'm curious as to what Tom thinks now about that goal, since the majority of his new designs don't appear to attempt that.
Rory, I'm sure that you mean well, but until you actually get around to building a speaker perhaps you should do a lot less talking and a lot more listening to guys like Peter who have.
Bob Russell
Post by: bgavin (Bruce Gavin) on May 22, 2005, 10:33:19 AM
The length question was raised on Bill's board, and he posted the following:
For the record, T36 is 300cm (9.84'), T30 250cm (8.2'), T24 170cm (5.57') , T18 and AT both 210cm (6.89').
The imperial values in parenthesis are mine, derived by calculator at 2.54cm per inch. Bill's values are those he inputs to McBean as part of his design process.
Post by: [x] on May 22, 2005, 03:57:07 PM
Post by: cmqt9 on May 22, 2005, 09:29:56 PM
Everyone who's anyone in the world of speaker design read the Tuba 24 article in Audioxpress. That magazine might not be what it was during the heyday of Speaker Builder in the '80s, but it's still the only magazine published in the US that has the likes of Vance Dickason, Reg Williamson, Joe D'Appolito and Nelson Pass listed as regular contributors, along with Bill Fitzmaurice. Please don't try to impress us because you read his article when anyone can log into his forum and ask questions of the guy who actually wrote it.
Word has it that Eminence is coming out with an improved version of the HL10a, improved in part from suggestions made by, guess who? Bill Fitzmaurice. That should come as no surprise, they're already recommending the Tuba 24 for the HL10a.
As to the stepped response curves of all the Tubas, they're there because they're supposed to be. Live music has a stepped response curve, and it only makes sense that speakers for live music should be designed for the requirements of the program material. Flat response below 35 Hz for live music sound reinforcement applications just isn't necessary.
Since the bulk of your knowledge on the subject seems restricted to textbooks, and since textbooks are at least 5 years behind the curve, your missing the point is understandable. But please, drop the moniker and call a spade a spade. Call yourself a pro after you actually become one.
Bob Russell, BS EE/AE
Post by: Michael_Elliston¶ on May 23, 2005, 06:44:52 PM
cmqt9:
| Quote: |
The only theoretical advantage for the Lab is extension below 20 Hz and then only if at least 8 cabs are clustered to get the necessary mouth area. |
I doubt extension will reach that low,but 4 cabs to 32hz is said to be solid.
When I see 'direct radiator mode' I shudder because what it means its low power input and high excursion. For guitar perhaps useful but not big reinforcement.
| Quote: |
I am only analyzing and relaying what I thought was common knowledge: The HL10 doesn't like oversized rear chambers |
When using modeling software this is easily apparent ~10litres vs ~50litres on the typical tuba drivers,obviuosly this is a result of the driver electromechnical specifications,and achieving a rear chamber of this tiny volume can be difficult as you point out.
We should all conclude that the tubas have a use and we all have different aims and preferences-its as simple as that.
Tom is being quite the gentleman regarding tuba vs labhorn(suggesting a shootout),I mean this is his forum,based on his design.
Mike.e
Post by: [x] on May 23, 2005, 09:00:29 PM
I sense a lot of ad hominem and unjustifiable appeal to lack of authority argumentation here when there are real, abstract principles involved in finding the actual answer. I have never experienced what it feels like to be a cone loudspeaker driver being ripped apart, so appeals to experience don't really fly here. Instead, explain to me and the rest of us why the Eminence Magnum 15 cone in the Tuba 36 will survive 25 Hz in direct radiator mode, and if it won't survive that treatment, explain why the Tuba 36 has any business in extending the driver Fs to such a low frequency. I and the rest of us on here will learn a lot more if we address the specific issue of the argument and not dismiss the argument out of hand just because I don't have a Ph.D in electrical engineering from Georgia Tech and 10+ years of experience in designing speakers professionally.
Post by: fernand on May 24, 2005, 12:22:05 AM
You state that in the Tuba 36, the magnum 15 will be ripped apart quickly at 25 Hz.
Can you explain on what model and which simulator you base your statement ?
I guess you have a model that generates with the magnum 95 dB at 25 Hz.
Could you predict a maximum spl or excursion ?
Post by: Michael_Elliston¶ on May 24, 2005, 02:44:56 AM
By loading I mean a meaningful airload applied to the cone of the driver thus providing output as opposed to below cutoff out of control excursion due to normal horn unloading...No magic that I know of. I dont see the point in extending the cutoff down low where its no use,a higher cutoff with same mouth area could result in a much nicer flat response to say 42hz but again its not how this design is for whatever reason.
I and the rest of us on here will learn a lot more if we address the specific issue of the argument and not dismiss the argument out of hand just because I don't have a Ph.D in electrical engineering from Georgia Tech and 10+ years of experience in designing speakers professionally
Too true.But then 'direct radiatior loading' saves the day so no proof is needed.
I hope this is a debate over design choices and not personal attacks.
Mike.e
Post by: Gareth James on May 24, 2005, 03:26:55 AM
Not knowing enough about the subject, and not being an experienced sound professional however i can't really comment.
Gareth James
Student of Sound
P.S. i just finished building a rough clone of the AG-Audio TS-118H, im using the Precision Devices PD186 driver. sounds pretty sweet to me, loud and reasonable extension.
LABsub vs. Tuba36 shootout sounds good to me!
Post by: fernand on May 24, 2005, 04:40:59 AM
| kaisersoze wrote on Tue, 24 May 2005 09:26 |
snip ... Current thinking seems to reveal that although extension to the lower frequencies is desirable in live sound, a flat response to those frequencies is not absolutely necessary in real-world applications. |
To be more precise:
* a flat maximum SPL level to the lowest frequencies is not (always) needed because the source level at those frequencies tend to be some 10 dB lower than the main contents
* a flat overall response is always preferred, but can nowadays be solved with EQ
This is combined with the fact that the dB's at those very low frequencies are by far the most expensive in terms of equipment, volume, power and cost, so correct dimensioning of that aspect is crucial for obtaining the optimal configuration.
Post by: cmqt9 on May 24, 2005, 08:23:16 AM
From Audioxpress April 2004 'The Tuba 24 Horn', Bill Fitzmaurice, page 36: "The resulting stepped response curve is not necessarily what you'd want for your hi-fi or home theatre, but for live sound it fits the bill perfectly."
Again, I'm not trying to belittle your status as a student at all, but your lack of practical experience is insurmountable. Your concern about system capabilites at 25 Hz shows this clearly. The answer to why a Magnum 15 in a Tuba 36 won't tear itself apart at 25 Hz at full power is an easy one: because with music program input it will never see full power at 25 Hz. Both rock concert and dance club RTAs show that at an average broadband SPL of 100dB the level at 25 Hz averages 60dB, some 30dB down from 50-60 Hz where the peak demand lies. At -30dB from full power not only is the Magnum 15 in no danger of tearing the cone apart, I daresay that an Alpha 8 would be equally safe.
Bob Russell
Post by: peter.golde on May 24, 2005, 10:05:26 AM
The Lab will unload much quicker below Fc than the Tuba36. In a single Lab there is a critical difference between 25Hz and 30Hz, at 30 Loads nicely, at 25Hz it is flapping in the breeze, so obviously we set the high pass at least 30Hz. The Tuba36 Unloads at a slower rate, the question is at what freq and power level do we reach xmax. Box modeling software will not predict this accurately in a Tuba. One way to find out is to drive the Tuba36 until it fails, several times at incresingly lower frequencies, or better, mount and wire a sensor to measure cone excursion and run sweeps. This would help us set our protection filters for different styles of music. With a properly constructed Lab we pretty much know where the limits are, thank you again Tom Danley.
Post by: [x] on May 24, 2005, 10:12:45 AM
Another issue: I notice a lot of you justify the lack of subbass output of most sound systems by the fact that most bass amp cabinets fall short below 60 Hz. The Eminence Delta 10 isn't even any good below 60 Hz. I recently loaned my friend one of my six EVTL606 cabinets with EVM-15L drivers, and he is surprised at the kind of low-end tone he can get from the driver. It sounds to me like he is even getting a good deal of the fundamental tone in there when playing with standard tunigs on the four-string. The driver in the low-tuned box has way more of the fundamental tone in the output than his Carvin 2x10 cabinet that he used to play through until he left it at a venue (something we still laugh about to this day) and even the Ampeg Classic 8x10 that was loaned to him afterwards. The Ampeg could hit you in the chest but you could tell it never got really low. It seems to me that in many cases it is impractically expensive to reproduce those low frequencies in an outdoor concert situation and for certain types of music like rock and bluegrass, and even a lot of DJ music. But what happens when the bass guitar is run through a direct box? Suddenly the limitations of the bass cabinet are removed from the signal chain and there are a lot of extra low harmonics as well as a strong fundamental. Why, then, would it not be desirable to attempt to reproduce at least the fundamental frequency of the bass guitar, if it is possible? Is it because of that "second-harmonic-is-louder-anyway-so-shut-up" phenomena? If so, I'll take your word for it and shut my face. I also realize that in live sound, it's only important to reproduce what pleases the crowd and gets you called back on the next show, so if that's the reason then I accept that as well.
Post by: cmqt9 on May 24, 2005, 10:40:51 AM
http://billfitzmaurice.com/RTA/Bass%20RTA.jpg
This is an RTA of an open E on electric bass running though an amp/speaker system that is flat to 25Hz. Both second and third harmonics at 80 and 120 Hz are better than 12dB higher than the fundamental at 40 Hz. But that still doesn't mean a Delta 10 is worth anything on bass, it dies below 90 Hz and doesn't have enough xmax to work well on anything but guitar.
Post by: Matt Loretitsch on May 24, 2005, 11:48:37 AM
-Matt
Post by: Tom Danley on May 24, 2005, 03:39:20 PM
While there are probably things a 1/3 octave RTA is good for, one should keep in mind it has significantly less resolution than your ears and so can easily hide something that sticks out like a sore thumb on a more appropriate measurement.
For measuring a loudspeaker, it is more than nothing or a sound level meter.
Also, keep in mind that it is an averaging measurement, which is fine if what you want to know is an average over some time. Pink noise (which normally has a +6 dB peak to average level, like the most HIGHLY compressed music) is the intended test signal fwiw.
If you want to know what lf components there are in music, one must look at the largest peak value even if they are low duty cycle.
An averaged measurement might not even show the transient signal that made the driver jump out of its box, yet one cannot deny its existence to the re-cone-er.
Rather than argue what spectrum there is in a concert and why, why not ask, what is there when all of the “practical” limitations are removed, such as in the studio?
Turns out, there is low bass in a lot of music and it is cool to reproduce it in a large scale and it is nothing like “can’t tell the difference”.
So far as the fellow cone heads go, the problem sort of boils down to;
How much cost size and weight are associated with producing enough low frequency to be “significantly audible” and how can you do that without the harmonic distortion components at 2,3,4,5 etc times the input F, from becoming so loud that they “muddy” the range above with that “free” sound that is unavoidable.
You know too, while Bill’s plans and web site have benefited from this forum, lets keep in mind that the LAB sub was intended for larger scale use.
It should for example be within a few dB of a BT-7 with about the same frequency response.
For example, I attended a U-2 concert at the world music theater (big half open shed) where Clare Bros had 100+ S-4 boxes per side for the upper part of the PA and 6 BT-7s per side for the VLF part. Get the picture, that’s hundreds of 18’s and while Clare traveled with 16 BT-7s they rarely needed them all.
A pile of 6 or more LAB’s per side would be scary too, made for large scale sound.
Also the LAB project was done for free by me and others, this is not “for profit” there are no plans to buy and if your interested, there is also some reading on “how and why” the LAB was designed.
I didn’t notice anything like that at Bill’s forum but maybe I missed it..
The Lab sub was designed to go down to about 32Hz in a group and to be as close as I could get “in the computer” to be unbeatable so far as Voice coil woofers go.
I figured that would be part of the fun, to turn something like that loose in the hands of other DIY’rs, something I would have dug myself 25 years ago.
Operating this at high levels significantly below 30 Hz (below the low cutoff on any box for that matter) is a mistake and I suppose a given in Pro sound that one uses a high pass filter for that reason. An exception would be when used in a room such as Brad Litz’s “home” system.
All this talk about the lab not being “small” makes me wonder if there needs to be a new project, then maybe we could compare two things of similar size.
Got to run.
Tom Danley
Post by: Michael_Elliston¶ on May 24, 2005, 07:08:45 PM
-Its a matter of opinion whether producing a stepped response through a flat system or a stepped response through a stepped system.I dont play guitar so I cant add my 2cents.
One would think that a flat response system would reproduce the guitar 'how its meant to be'Whether people have been doing that or not is another matter
I dont think we need another lab project-the punisher does the kicks nicely.
Mike.e
Post by: peter.golde on May 24, 2005, 08:51:53 PM
"I dont think we need another lab project-the punisher does the kicks nicely."
Are you insaine? The man just offered a new project!
Since his latest Danley Labs subs claim to be the most powerful on the planet, I wouldnt mind being thrown a few crumbs from that.
Post by: Brad Litz on May 24, 2005, 09:42:08 PM
| Tom Danley wrote on Tue, 24 May 2005 14:39 |
Operating this at high levels significantly below 30 Hz (below the low cutoff on any box for that matter) is a mistake and I suppose a given in Pro sound that one uses a high pass filter for that reason. An exception would be when used in a room such as Brad Litz’s “home” system. |
I am using a 2nd order high pass filter to my LABsubs that is 3dB down at 20Hz. I have a Furman peak reading watt meter connected to one of the LAB's which are each driven by separate 400 watt amps. With bass heavy music at very high volume I occasionally see the 10 watt light blink. With unexpected special effects I once went just over 50 watts. The audience (myself included) were more than a little scared by that
Post by: Sam Jayaraj on May 25, 2005, 01:45:39 AM
| Tom Danley wrote on Wed, 25 May 2005 01:09 | ||||||||||||
Hi Guys Also the LAB project was done for free by me and others, this is not Post by: Mark Seaton on May 25, 2005, 10:16:15 AM
Hi Brad, You might want to try taking some measurements and listening a bit without the hi-pass. In any confined room you will see a good deal of gain at low frequencies, where I would expect to see a shelved response to the low end of your system. The question is just how much maximum output you have down low from the combo of amps and subs. If sailing without a hi-pass is a bit too much, experiment with Bessel fitlers in your DSP as when set to 20Hz they will extend a little lower before the response drops more abruptly. Even this can be sculpted a bit with a shelf filter above the low cut-off. Obviously the above isn't a common practice for sound reinforcement, but the concept of being aware of output limitations and the corresponding requirements of your application are still quite important. In applications with lower output requirements you can certainly goose the low end quite a bit. At the same time, in some very high output or very large coverage applications you may end up high passing the system even above its nominal useful low end. In such cases, the decision has little to do with "unloading" but everything to do with helping the sub maintain composure under higher peak levels. In such cases, knowledge of the impedance curve can also be useful in understanding what you are asking from your amplifier. In the end realize that while it is certainly possible to determine levels and conditions at which a setup won't go into duress, but better understanding of the operation and capabilities will allow you to contour things appropriately for the application at hand while coming away with fewer component failures. Best Regards, Post by: John Chiara on May 25, 2005, 01:51:17 PM
I totally agree..and I believe this is what is usually missing from live sound reinforcement and what the future holds if enough of us can have our say. The lacking lower octave+ in most systems is what ..IMO...keeps the music from achieving the intimacy it could..if those lows are reproduced. I mix in the studio for my day job..with a sub flat below 20HZ..and far from being a "special effect" situation...it grows on you as a satisfying completeness that is sorely missed if removed. This is useful in mixing recordings but I believe even more so in reproducing live music in the 21st Century. Post by: Michael_Elliston¶ on May 25, 2005, 07:01:36 PM
No doubt It would be a good product,but wouldnt contain any patented fun goodies
Post by: Timmahh on May 25, 2005, 07:31:19 PM more later. Post by: fernand on May 26, 2005, 07:05:14 AM
Interesting, could you tell us from your experience what sorts of energy you are seeing in the low spectrum ? Post by: John Chiara on May 26, 2005, 11:18:23 PM I totally agree..and I believe this is what is usually missing from live sound reinforcement and what the future holds if enough of us can have our say. The lacking lower octave+ in most systems is what ..IMO...keeps the music from achieving the intimacy it could..if those lows are reproduced. I mix in the studio for my day job..with a sub flat below 20HZ..and far from being a "special effect" situation...it grows on you as a satisfying completeness that is sorely missed if removed. This is useful in mixing recordings but I believe even more so in reproducing live music in the 21st Century. [/quote] Interesting, could you tell us from your experience what sorts of energy you are seeing in the low spectrum ?[/quote] First thing you find is all kinds of junk!!! It is..IMO.. necessary to run aux fed subs if at all possible....although with a real low frequency reproduction the overall sound is better than with a system with a big hump at 50-80hz. The main thing is that you get to hear the actual sound of many instruments that put out stuff in the 20-40hz area. In my experience having that extra octave makes it easier to balance kick and bass...frequency wise anyway..and even dynamically, having sufficient oomph down thaere feels very different from the boomy, muddy live venue sound we normally hear. The whole impression of "fidelity" changes..things sound cleaner, more open, more detailed..I think one reason is the extra low extension lets the fundamentals of lower instruments actually exist without being "cramped" by a restricted response. Synths tracks that actually sound full range are a different beast than what we are used to. I could go on subjectively but objectively I beleive that in practice "linear transfer"..meaning 'what goes in is what what comes out'..is at least approachable on the low freqency end...and I have not often..or ever..actually heard that in a live situation..but I do hear a whole bunch of other "crap" that seems to pass for low end..totally unnecesary with Labs, BassMaxx, BDeaps and Tom Danley's new sub models around. What needs to happen first is the pursuit of this as an ideal and then the tide can change. I am on board. Short term demos can help but I find a little "break in " time is often needed for the new response to become familiar enough to the conditioned brains of listeners to catagorize the resulting physical sensations as pleasant..but once it settles in there is no going back...PLUS one positive side effect is that listeners become comfortable with lower playback levels..a good thing for everyone..especially those of us working day after day at FOH. Post by: fernand on May 27, 2005, 01:28:01 AM could you tell us from your mixing experiences at what level the 20, 40, 60 , ... Hz signals are sitting in respect with the average signals ? Post by: Alan Searchwell on May 27, 2005, 06:09:39 AM Please consider your audience when you say things like: [quote title=BHFProfessional wrote on Sun, 22 May 2005 14:57] And I didn't have to blow up an expensive driver to learn that information (though I extend my condolences to anyone who did, as there are better and less costly ways of learning that info.) There are people on this board who have large multiples of the $135 cost of an Eminence HL-10 invested in their systems. For example $400+ would be considered a good deal on the Seismic 8196, Aura 1808 or McCauley 6174 that are used to load Bassmaxx cabinets (I think the list price is about twice that). Another example is the EAW SB1000 available at Music Center for $2,240. Not including labour, my prototype LAB cost me about $1000 complete with Rhino lining, 5 inch wheels and perforated metal grille but there are people who have had material cost them as little as $700. There are people on this board who have more than 8 LABs, heck I remember a guy in New Zealand saying he's planning to build 50! I plan to build four more and here in Jamaica that does not even qualify for entry into the real live sound market where I have seen 16+ SB1000 being used per side. Just think of how you must sound to some of these guys when you call a $135 speaker expensive! [quote title=BHFProfessional wrote on Tue, 24 May 2005 09:12] I also wanted to bring those concerns to your attention, after which I promptly had four or five people's feet broken off in my behind. Perhaps I wrote too authoritatively when I should have been phrasing more of the stuff as a question. Yes, perhaps you did and perhaps you "wrote too authoritatively" some time back when as I remember you saying that "person A" should do this and that and so forth to his design to achieve what you think will be better results meanwhile the "Crusher" remains on the drawing board. "Youth-full Exuberance" is the term that comes to mind. Tom Danley signs his posts "Tom Danley", Mark Seaton signs "Mark Seaton, Seaton Sound, Inc., Danley Sound Labs". In the case of Mark, both companies exist and and have some credibility. You on the other hand cite two imaginary "commercial ventures" which you proudly attach to your signature and then wonder why people stomp on you. Hmmm, are you trying to equate yourself to these gentlemen. It'll take quite a few years and some SOLID ACHIEVEMENTS to earn that kind of respect. The remarkable thing about the LAB Sub is that the lead designer is somebody with considerable experience who, has made and is likely to continue to make, a good living designing speakers. He has led the design of a product that approaches the performance of his own proprietary design (BT7) and made it available under a licence that protects him from commercial exploitation while allowing DIYers AROUND THE WORLD considerable leeway. Through this project DIYers have a subwoofer that can hold keep up with and even outperform commercially available touring class products that cost more than twice as much. Bill's designs, though quite remarkable in their own right cannot match all these criteria. There are people reading who have been lurking since the LAB Sub project was originally proposed back on "ye old Live Audio Board" who have only posted a fraction of the amount of times the exuberant Mr. Buszka has. Nonetheless it has been quite interesting although sometimes a tad irritating to read his posts. I suppose most of us have learned something. Carry on. Oh, and thanks again Tom! Post by: Michael_Elliston¶ on May 28, 2005, 11:19:21 PM I really dont see a problem with pursuing the bottom octave,or the top octave(that alot of HF horns miss)-but again it comes down to size,cost,transportation costs. Bottom octave!! http://www.speakerplans.com/forum/forum_posts.asp?TID=1525&a mp;PN=1 http://roborg.freefronthost.com/infra-horn.htm 
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