Corner bass traps made out of linacoustic? - AVS Forum
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post #1 of 14 Old 03-28-2012, 04:52 PM - Thread Starter
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I finally getting ready for wall treatments for small 12'x18'x7.5" theater. I planning on 1" linacoustic for the entire front wall, and at ear height and below on the side and back walls. The upper back and side walls will get 1" worth of poly-batting to fill it out and all will be covered with some dazian epxo cloth fabric.

Whit this small theater I'll have some left over linacoustic from my 100" roll. Assuming I have enough, would this be a good material to use to make 17"x17"x24" super chunk bass traps in the front corners? I read most people are using OC 703 which I think has very similar acoustic properites as the linacoustic. It sounds like the 703 might be more rigid than the linacoustic though. I couldn't find a local dealer for the OC703 so I was hoping the linacoustic would be an acceptable substiute for the 703 for a corner trap.

Another option with the extra linacoustic could be to use 2" instead of 1" on the front wall? I think the bass traps would be more desirable though in the small room.

Thanks
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post #2 of 14 Old 03-29-2012, 12:47 AM
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For the superchunk bass traps, you are going to get recommendations to use R13/R19 pink fluffy insulation instead of linacoustic or 703. In lamens terms, it's because in the corners of your room, there is less velocity so less dense insulation works better. Others can chime in with more details.

As for the front wall, the thicker the better so 2 inch would be a worthwhile use for the rest of your line acoustic. Something else to consider for the front wall is to use a membrane (thin saran wrap type plastic, the stuff construction workers use to lay over carpet while working) in between the layers of your linacoustic. This will help with the lower frequencies a bit more than two layers alone. Again, more detailed info can be had from others, hopefully they will chime in


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post #3 of 14 Old 03-29-2012, 03:55 AM
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5000rays/m flow-resistivity (pink fluffy) becomes a good choice at 34" faced chunks and thicker. for 24" faced i would use a material with higher GFR,
regardless, for porous-only (velocity-based) LF absorbers, they need to be sufficiently thick (spaced away from rigid boundary such that the insulation is placed into relative areas of high particle velocity for a given wavelength) to be effective - and the thicker the trap, the lower the GFR of the material you will want to utilize.
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post #4 of 14 Old 03-29-2012, 05:19 AM
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Quote:
Originally Posted by Digital_Chris View Post

In lamens terms, it's because in the corners of your room, there is less velocity so less dense insulation works better. Others can chime in with more details.

there isn't a correlation between "less velocity" and "less dense insulation", as you imply.

...although speed of sound does change in the porous absorber
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post #5 of 14 Old 03-29-2012, 08:07 AM - Thread Starter
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So i'd be better off making the screen wall 2" (id have enought to do even 3") and then use the fluffy pink chunks for corner bass traps?

A 100' roll of linacoustic is a little pricey so I'd like to be able the use the leftovers (approx 40' x 4') if at all possible. But at the same time I don't want to use the leftovers if it would produce a negative effect.
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post #6 of 14 Old 03-29-2012, 10:03 AM
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docquest, have you read this thread?
Early reflection panel thickness...

Mike R,P.E. clickable DIY hot links:

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post #7 of 14 Old 03-29-2012, 10:43 AM
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Quote:
Originally Posted by localhost127 View Post

the lower the GFR of the material you will want to utilize.

I've Googled and looked at other threads can't find a definition of GFR


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post #8 of 14 Old 03-29-2012, 11:49 AM
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gas flow resistivity.
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post #9 of 14 Old 03-29-2012, 12:12 PM
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Quote:
Originally Posted by localhost127 View Post

there isn't a correlation between "less velocity" and "less dense insulation", as you imply.

...although speed of sound does change in the porous absorber

Oops, I messed that up. I guess I got my words jumbled because of all the bass trap talk... velocity-based traps, pressure-based traps (i.e. non velocity-based traps), etc. I guess velocity isn't the issue in corner traps, not as much as pressure anyway? Although, if the velocity never really changes, why is a higher "GFR" absorber not recommended? Is it because with the higher pressure in the corners, a lower GFR absorber is the key because it's easier to turn pressure into heat? Therefor, velocity is the lesser of the concern?

Honest question


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post #10 of 14 Old 03-30-2012, 11:16 AM - Thread Starter
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Quote:
Originally Posted by mtbdudex View Post

docquest, have you read this thread?
Early reflection panel thickness...

Thanks for the heads up on that link. That was a great thread (at least the parts I could understand). Since its taken me so long to get to this point already I think I'll try a some experimenting with amount and location of the linacoustic.

The room is currently drywalled and the kids and I have been watching stuff ocassionally down there the last few months. Even in its current unfinished state we all think its sounds pretty good. Thats part of the reason its been taking so long to get the room done, I never should have installed the projector.
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post #11 of 14 Old 03-30-2012, 11:29 AM
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Quote:
Originally Posted by Digital_Chris View Post

Although, if the velocity never really changes, why is a higher "GFR" absorber not recommended?

Honest question

dont confuse particle velocity (velocity and pressure are inversely proportional) with the speed of which sound propagates.
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post #12 of 14 Old 03-31-2012, 12:35 PM
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Quote:
Originally Posted by localhost127 View Post


dont confuse particle velocity (velocity and pressure are inversely proportional) with the speed of which sound propagates.

Still a bit confused, but that's ok, I'll understand someday, as soon as you start replying in lamens term for peeps like me :-P


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post #13 of 14 Old 03-31-2012, 04:02 PM
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Quote:
Originally Posted by Digital_Chris View Post

Still a bit confused, but that's ok, I'll understand someday, as soon as you start replying in lamens term for peeps like me :-P

ok me too.
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post #14 of 14 Old 04-01-2012, 10:44 AM
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Sorry, Layman's Terms, understand now? Forget it man..


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