Acoustical Treatments Master Thread - Page 347 - AVS Forum
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post #10381 of 10384 Old 07-11-2014, 09:22 PM
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Originally Posted by badger985 View Post
I was looking to make corner bass traps, and was going to buy Owens Corning 703 and cut them into the correct dimensions, however when doing research I found the following

Owens Corning "Select Sound" Black Acoustical Board 2" inch thick has an NRC of 1.00 the same as 703, but it also states that this reduces sound reverb, which 703 does not. Would this be a better product to create Bass Traps out of?

To answer your last question first "Would this be a better product to create Bass Traps out of?"
No.
Please see: http://www.bobgolds.com/AbsorptionCoefficients.htm
look for 703, and compare it against Black Acoustic Board at {125hz, 250hz, 500hz, 1000hz, 2000hz, 4000hz}
There are lots of things very similar to 703, and anything that's similar is just fine.


The 'reverb' comment just seems odd to me. Either used correctly should take care of reverb. Either used insufficiently will not take care of reverb. A myriad of other things can be used to take care of reverb.

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post #10382 of 10384 Old 07-11-2014, 09:32 PM
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Originally Posted by coolgeek View Post
I am looking to build a gentle diffusion.. and was thinking of using those 'vinyl tiles' that people use for flooring would work?

Do the vinyl absorb the sound or reflects them? If they absorb, then it won't work.

I was thinking of getting those and then bend them to semi-round... it's easy to build.. just put a bunch of them in right angles, bent into half round shapes...

Basically something like below (contour type diffusers) but built out of vinyl floor tiles rather than wood:



Vinyl will reflect some frequencies (higher f), and transmit (through it) other frequencies (lower f).
Generally speaking, anything more solid than 1/8" Masonite is ok as a diffuser.


The frequencies it has a hope of diffusing are proportional to the size of each.
The rule of thumb is:
- at wavelengths significantly smaller than the object, get defused as light bouncing off a curved mirror.
- wavelengths significantly larger than the object, ignore the object
- wavelengths the same size as the object, reflect randomly.


With all of these being identical, spaced identically, you might get lobbing effects. Random sizes with random placement, give better diffusion.

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post #10383 of 10384 Old 07-12-2014, 09:30 AM
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Originally Posted by BasementBob View Post
To answer your last question first "Would this be a better product to create Bass Traps out of?"
No.
Please see: http://www.bobgolds.com/AbsorptionCoefficients.htm
look for 703, and compare it against Black Acoustic Board at {125hz, 250hz, 500hz, 1000hz, 2000hz, 4000hz}
There are lots of things very similar to 703, and anything that's similar is just fine.


The 'reverb' comment just seems odd to me. Either used correctly should take care of reverb. Either used insufficiently will not take care of reverb. A myriad of other things can be used to take care of reverb.
Great Thanks.

Just to clarify the 703 FRK only has the foil reinforced on one side, thus if I slap that together with a regular piece of 703 2" to create a 4" trap, I will still get the benefit of the Foil Craft, and the enhanced Sound absorption at 125hz?

Thanks again.
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post #10384 of 10384 Old 07-12-2014, 12:37 PM
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Just to clarify the 703 FRK only has the foil reinforced on one side, thus if I slap that together with a regular piece of 703 2" to create a 4" trap, I will still get the benefit of the Foil Craft, and the enhanced Sound absorption at 125hz?

Skip the FRK/foil. Membrane absorbers require an expert. If you understand how to make a membrane absorber, and how to measure/calculate the effects of existing wall resonance on the membrane, you're better than me. If you measure and discover you need a tuned membrane absorber to deal with a pesky room mode, look at a professional one like RPG Modex.


Mineral wool (including fiberglass), and corner traps, of just mineral wool and acoustically transparent cover fabric, are idiot proof.


1) soundproofing is good
2) knock first reflections down by at 20dB
3) deal with room modes. Minimalist techniques include tri-corner traps and subwoofer placement.
4) no chairs higher than your shoulders
5) wide frequency absorption, not high frequency absorbers

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Last edited by BasementBob; 07-12-2014 at 12:46 PM.
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