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Author Topic: LabSub vs. Tuba36/Tuba36Slim  (Read 17406 times)

Michael_Elliston¶

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'Michigan subwoofer shootout'
« Reply #10 on: May 17, 2005, 04:29:18 pm »

If the Tuba is 5cubic ft smaller,something has to give according to hoffmans iron law.

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
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bgavin (Bruce Gavin)

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Re: LabSub vs. Tuba36/Tuba36Slim
« Reply #11 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.
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Sam Jayaraj

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Re: LabSub vs. Tuba36/Tuba36Slim
« Reply #12 on: May 18, 2005, 03:05:32 am »

Hai Tom,

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?
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Sam

cmqt9

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Re: LabSub vs. Tuba36/Tuba36Slim
« Reply #13 on: May 18, 2005, 07:07:39 am »

Bruce, have you seen this?

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.
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bgavin (Bruce Gavin)

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Re: LabSub vs. Tuba36/Tuba36Slim
« Reply #14 on: May 18, 2005, 09:18:11 am »

Yes, I saw that.

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.
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fernand

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Re: LabSub vs. Tuba36/Tuba36Slim
« Reply #15 on: May 18, 2005, 11:06:33 am »

Bruce,

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).
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jeffhtg (Jeff Kenney)

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Re: LabSub vs. Tuba36/Tuba36Slim
« Reply #16 on: May 18, 2005, 03:03:51 pm »

what power levels have you suggested tom?? i must have missed that one Smile

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bgavin (Bruce Gavin)

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Re: LabSub vs. Tuba36/Tuba36Slim
« Reply #17 on: May 18, 2005, 05:21:32 pm »

Fernand,

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.
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Elliot Thompson

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Re: LabSub vs. Tuba36/Tuba36Slim
« Reply #18 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,
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Elliot

fernand

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Re: LabSub vs. Tuba36/Tuba36Slim
« Reply #19 on: May 19, 2005, 01:15:09 am »

Bruce,

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.
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