# ? about constructing acoustic treatments



## tenzip (May 4, 2007)

Hello, I bought 10 4'x2'x2" Knauf 3lb/ft^3 panels today, and I have some questions about construction/covering. I intend to use these as they are to cover 1st reflection points, and also build some corner bass traps by chopping them up in triangular pieces.


What effect, if any, would having the fiberglass panels or traps wrapped in polyester batting before wrapping with fabric? The thought here is just to keep fibers from escaping.
What effect would gluing the triangular pieces together in a stack have? Using something like liquid nails or similar.
Is there much (or any) advantage to hanging the wall panels out from the wall an inch or two?
What kinds of fabric are suitable for wrapping the treatments with besides burlap? I seem to remember reading somewhere that a poly or cotton knit would work just as well as burlap.
Is there any acoustic reason the 2'x4' panels can't be cut diagonally, (to form two skinny right triangles) and then mounted an inch or two apart?

The last is purely for aesthetic reasons. They would still form a rectangle on the wall, but would have a bit more flair, I think, by having a diagonal line in the middle, and they could also be different colors. It also seems to me that this would actually expose more surface area, so would it potentially be better?

At this point, I have not done any measurement to determine what all I need, or to have a baseline for comparison purposes, but I have some trouble understanding dialogue from time to time, and simply turning up the volume is not always an option. I will be doing some in-room measurements in the future, and plan on making all treatments easily movable/removable, so I can still get a baseline.

TIA for your help.


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## bpape (Sep 14, 2006)

1. It'll have basically no effect.
2. If anything, it would be negative. No need to glue.
3. Sure. Building a frame so that you can leave a gap in the back will extend the low frequency efficacy of the panels. Don't go more than the thickness of the absorption though.
4. Try Muslin
5. Should be just fine. 

Don't count on corners to deal with 100% of the bass issues. They'll be effective in decay time for sure - however - not all frequency related bass aberrations will be addressed with corner treatment. Take some measurements, smooth the best you can via placement of seating, sub, and speakers - then look and see what you still have left to address from a FR standpoint. That'll point you in the right direction.

Bryan


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## tenzip (May 4, 2007)

Bryan,

Thanks for the quick reply. The room is not in it's final configuration yet, so this is basically just throwing something at it to try to increase the intelligibility of the dialogue. Measurements and more considered placement will come later.

Your response brings up another question. Is there any harm in having the corner treatment out from the wall an inch or thereabouts? Or are they more efficient if placed tight into the corner?

And something that occurred to me early this morning: Will a very light coat from a spray can have any or much effect on reflection/absorbtion? I'd like to tame the "whiteness" of the polyester batting before wrapping with fabric.


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## bpape (Sep 14, 2006)

You can certainly have them out an inch or so - you're still getting the bulk of the effect.

I'd strongly resist doing any kind of paint or coating - unless you want to minimize the amount of high frequency absorbtion. If you want it to still be absorbant, I'd use some black muslin under whatever final material you're going to use. 

Bryan


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## tenzip (May 4, 2007)

Again, thank you for the quick reply. I guess having a 2 layers of fabric was just too easy.


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