Width of bass trap performance questions

[Wiz_Oz]

I have searched around and couldnt find any answers...


I am wondering if anyone has tested the performance of differing "widths" of insulation functioning across the corners as bass traps.

I have sheets that are 8ft by 4ft of tontine acoustisorb 3. (2" thick)

I am wondering about leaving them 4ft wide and 8ft high and putting two of them together for a total thickness of 4". Framing them and using them across the corners. (i have the room size to do it....3.85m by 7.87m)

as oppsed to the normal 4ft by 2ft traps you see...which I am assuming came to be, mostly because 703 and rockwool are those sizes..

anyone have any info they can point me too?


I also wonder about having one sheet as 8ft by 4ft with the second sheet behind it 8ft by 2ft. any thoughts.

cheers and thanks

Wiz

[spm_gl]

A wider trap over the corner means you can have a greater total depth, so you have a lower absorbtion frequency limit. Additionally, more width means more area means more absorption over all. The 2x4 is simply dictated by the usual material size.

[DanDan]

There is extensive information about SuperChunks at their 'home' studiotips.com. I haven't seen any tests comparing your variation. It would of course work and a wider panel will by definition be farther from the corner and thus operate into a lower frequency area.
There are practical difficulties with such a span, and there are more proven high performers.
Consider the fully filled corners. There are comparative tests that suggest a filled corner blows away a straddle panel. Acoustics Forum • View topic - Corner Absorption Comparision test
Note if you are doing a filled corner, there is an optimum width in terms of a cut pattern, not to waste insulation. 60cm or 32 inches. The cut patterns are on that website also.
DD

[Ethan Winer]

Originally Posted by Wiz_Oz

I am wondering if anyone has tested the performance of differing "widths" of insulation functioning across the corners as bass traps.

The closest data I have is the comparison between 17-inch wide Auralex LENRDs and my company's 24-inch wide traps on our Product Data page. It's not a great comparison because LENRDs are made of foam, but on balance they fill the corner all the way.

Bottom line with all bass trapping is the bigger the better, and the lower in frequency they absorb well to.

--Ethan

[Wiz_Oz]

Thanks everyone for your help and tips.

I spent yesterday building a test unit.....man it took a while....8ft by 4ft seemed like a good idea at the time...8)....It just looks too big!! there are a bunch of issues because of the size...getting the hessian to look good, keeping the large sheet of tontine in place....

Also the change to the room sound, with just that one sheet was really significant ( i dont have measuring REW set up yet, just talking about using my ears) such that, I think I might not need as much treatment as I originally thought...

More testing today, but I think I will head down the path of 4 by 2 feet absorbers for RFZ points, and stack two of them in the corners for bass traps....

again thanks very very much...

cheers

Wiz


PS and a hearty thanks to all the people who have posted free and informative info on the WEB about studio acoustics....its just sensational.

[DanDan]

Glad you tried it. Rather you than me! I would urge you to consider SuperChunks. They take up the same amount of space, but have much more performance.
DD

[Wiz_Oz]

Originally Posted by DanDan

Glad you tried it. Rather you than me! I would urge you to consider SuperChunks. They take up the same amount of space, but have much more performance.
DD

Hey DanDan

I have considered the superchunks....but its a cost/performance benefit question.

with my tontine sheets being 2400 by 1200 and 50 thick...and I would want them to go 2300 up in height....(unless my maths is wrong)...

I would get 16 triangles of 600 width at 50 thick...which means to fill a corner 2300 high would require 46 triangles or nearly 3 sheets. Where as a 2400 by 600 100mm thick bass trap would require only 1 sheet. I have never seen data, showing the difference in performance between those two.


Each sheet of tontine has cost me 50 AUD so the cost is considerably different for each bass trapping corner style (SC $150 vs Panel $50)...and given I have a finite amount of sheets (12) I am looking to use them most effectively.

I cant tell how much bass trapping I need till I start measuring the room and adding traps, and I can always cut a rectangle into triangles, but the reverse would be difficult....8)


Also, I have found plenty of threads, where people say, superchunks are better, and if you have the material go for it...but I have never come across a post, that has given me definative data...on cost/performance...

Eg, superchunks in corners, vs 100mm thick panels, and someone using REW or similar to show the results...

If anyone knows of such a thread I would love to read it....


thanks so much for your interest and help

cheers

Wiz

[Wiz_Oz]

Originally Posted by DanDan

There is extensive information about SuperChunks at their 'home' studiotips.com. I haven't seen any tests comparing your variation. It would of course work and a wider panel will by definition be farther from the corner and thus operate into a lower frequency area.
There are practical difficulties with such a span, and there are more proven high performers.
Consider the fully filled corners. There are comparative tests that suggest a filled corner blows away a straddle panel. Acoustics Forum • View topic - Corner Absorption Comparision test
Note if you are doing a filled corner, there is an optimum width in terms of a cut pattern, not to waste insulation. 60cm or 32 inches. The cut patterns are on that website also.
DD

And If I had read this better, I would have realised you pointed me towards the information I seek.....sorry for missing this and thank you...I am off to read and absorb (pun intended...8)...)

cheers and thanks

Wiz

[Wiz_Oz]

Well well well...

thanks so much for that info DanDan.....I was so wrong with my maths...I would yeild 32 triangles of 50mm per 2400 sheet....mmm..reconsider time..


thanks again

Wiz

[Glenn Kuras]

I would like to point something out that I think is pretty important.

3) This test uses only 8 linear feet of corner for testing and would not be suitable for comparison to tests taken with larger specimens counts as the smaller than typical sample size used in this experiment would tend to exhibit higher absorption numbers than a test with a larger sample size. Nonetheless, these tests are valid comparisons of the included specimens. All of the data sets below were collected in the same configuration for each specimen set, in the same lab, on the same day.

This is pretty important and can throw testing off pretty bad. Not that the test is not useless but not sure I would use it as any kind of reliable data.
If you want to see how well filling the corner works our Tri Trap would be pretty darn close. You can see the numbers here.
GIK Acoustics: GIK Tri-Trap

[DanDan]

Hi Glenn, interesting quote. Who said that? It seems to be saying that a relatively small sample may show higher absorption than a proper large sample. I am having a bit of trouble with that one. Why or how? I would have presumed the opposite. Large samples are used so that they are significant in the large rooms used for testing. Testing rooms have to be large in order to achieve a diffuse field at low frequencies. A small sample in such a large space would clearly have a 'signal to noise' issue. i.e. Would change the RT very little and thus be hard to deduce it's absorption.
But that's just an interesting aside. If we ignore the actual Sabine figures, using the studiotips test for comparison only, it is clear that filled corners are quite superior to straddled. Intuition and your own TriTraps tests confirm.
DD

[Ethan Winer]

Originally Posted by DanDan

Large samples are used so that they are significant in the large rooms used for testing. Testing rooms have to be large in order to achieve a diffuse field at low frequencies. A small sample in such a large space would clearly have a 'signal to noise' issue. i.e. Would change the RT very little and thus be hard to deduce it's absorption.

Exactly. This is why ASTM demands at least 60 square feet of surface. And that's at 100 Hz and above. Down around 50 and 63 Hz I'd think you need at least four times that to get reliable data. Even just for comparison.

My partner Doug and I came very close to testing many different sizes and shapes a few months ago. I want very badly to do this test for "public knowledge." But it would have cost us nearly $1,000 just for material that we'd have to cut up and be unable to reuse, plus at least 20 man-hours of our time. So we decided not to do it. But I will some day. I promise.

I have some other related testing in the works, and I'll share the results soon.

--Ethan

[Wiz_Oz]

Originally Posted by Glenn Kuras

I would like to point something out that I think is pretty important.



This is pretty important and can throw testing off pretty bad. Not that the test is not useless but not sure I would use it as any kind of reliable data.
If you want to see how well filling the corner works our Tri Trap would be pretty darn close. You can see the numbers here.
GIK Acoustics: GIK Tri-Trap

thanks so much for taking the time and effort to reply Glen....

Unless I misinterpret the data sheets (and there is every chance of that I might add.........

It seems that the TRI TRAP and the 244 are very similar(with the 244 being corner mounted)....is that what you are alluding too?


Maybe, I should ask a more direct question...thumbsup...of both you and Ethan.

If you were me, apart from cursing the gods for your unfortunate luck, would you either

A) build superchunks 8ft high

B) 4" panels and straddle the corners two panels stacked on each other to same height ...8ft.


I am having real trouble sifting through the information, and the incredible amount of opinion on this subject.

If either your product, or Ethans were available in Australia, at a price that didnt mean I would have to sell of one of my kidneys....I would purchase either or....(and its not you guys fault, its mine for living so far away....)

But alas, I have to DIY.

I really really dont want to cut this stuff up into triangles, if I dont have to....if the improvement is minor, of superchunking over straddling, then straddle it is...


appreciate your input...

cheers

Wiz

[Wiz_Oz]

Originally Posted by Ethan Winer

Exactly. This is why ASTM demands at least 60 square feet of surface. And that's at 100 Hz and above. Down around 50 and 63 Hz I'd think you need at least four times that to get reliable data. Even just for comparison.

My partner Doug and I came very close to testing many different sizes and shapes a few months ago. I want very badly to do this test for "public knowledge." But it would have cost us nearly $1,000 just for material that we'd have to cut up and be unable to reuse, plus at least 20 man-hours of our time. So we decided not to do it. But I will some day. I promise.

I have some other related testing in the works, and I'll share the results soon.

--Ethan

Do the test before I spin up the angle grinder and I will kick in 50 bucks....8)


cheers

Wiz

[Glenn Kuras]

It seems that the TRI TRAP and the 244 are very similar(with the 244 being corner mounted)....is that what you are alluding too?

Sure but the 244 is much more effective then a normal 4" standard 703 in the corner.

A) build superchunks 8ft high

B) 4" panels and straddle the corners two panels stacked on each other to same height ...8ft.

A for sure as it absorbs much more below 60 hz, but there is NOTHING wrong with "B" as it would use less material. It really comes down to your budget.

If either your product, or Ethans were available in Australia, at a price that didnt mean I would have to sell of one of my kidneys....I would purchase either or....(and its not you guys fault, its mine for living so far away....)

mmmmmmm your kidneys aren't worth very much.

I really really dont want to cut this stuff up into triangles, if I dont have to....if the improvement is minor, of superchunking over straddling, then straddle it is...

Understood so go with the 4". If you can swing the funds go with them 6". . In fact if nothing else build a few 6" ones for the back wall..

[Wiz_Oz]

Originally Posted by Glenn Kuras

Sure but the 244 is much more effective then a normal 4" standard 703 in the corner.



A for sure as it absorbs much more below 60 hz, but there is NOTHING wrong with "B" as it would use less material. It really comes down to your budget.



mmmmmmm your kidneys aren't worth very much.



Understood so go with the 4". If you can swing the funds go with them 6". . In fact if nothing else build a few 6" ones for the back wall..

Done and dusted....


Thanks so much for your help and advice....greatly appreciated...


cheers

Wiz

[Glenn Kuras]

Originally Posted by Wiz_Oz

Done and dusted....


Thanks so much for your help and advice....greatly appreciated...


cheers

Wiz

Pictures??

[Wiz_Oz]

QUOTE=Glenn Kuras;4581344]Pictures??[/QUOTE]



Sure, i will post photos up when i finish em....


thanks again

Wiz