Need to fix room decay time of 1500ms - Home Theater Forum and Systems - HomeTheaterShack.com

 
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post #1 of 4 Old 06-21-16, 01:30 PM Thread Starter
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Join Date: Oct 2013
Location: Mostly London
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Need to fix room decay time of 1500ms

Hi everyone. Can I get some help in damping my cinema room? Although there is a 35dB swing around 50 Hz, it is the ringing that is worrying me the most. The room is mostly concrete and rings like a bell. The REW waterfall shows everything below 110Hz taking as long as 1500ms to decay. That's a bad thing I'm guessing this is going to need a lot of bass absorption.

The room is 20' x 15', with 16" soffits on the sides and back walls. I'm thinking of starting with triangular, mineral wool absorbers under the soffits (13" on wall x 16" underside x 20" diagonal), with a run of about 14' on each side. I understand that bass absorption needs lots of depth but I'm thinking that some of the sound travelling along the length axis would see a 14' deep absorber.

My question is whether this is worth the effort and a good place to start? There is a wall behind my AT screen for other bass traps but I thought that doing the soffits first would help me choose later the best type of absorber on the front wall.

Many thanks.
Ion
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post #2 of 4 Old 06-21-16, 03:23 PM
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Quenten
 
Join Date: Jun 2007
Location: Tallahassee, Florida
Posts: 2,454
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Re: Need to fix room decay time of 1500ms

Brian is the master on this subject. I suspect that he will recommend something soon.

I think you could plan on say 2" ridged fiberglass on the front wall with corner bass traps. 4" traps @ the 1st reflection points on the side walls. The back, a combination of diffusion & absorption + corner bass traps. Running corner traps along the top of the side walls will help as well.

We would love to see some pics of your room!
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post #3 of 4 Old 06-22-16, 05:38 AM Thread Starter
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Join Date: Oct 2013
Location: Mostly London
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Re: Need to fix room decay time of 1500ms

Thanks Tonto, I think you're right. There is nearly 16" behind the screen which I can probably use for bass absorption, although not sure if its better to fill with fiberglass or mix/match with membrane panels...

The room is WIP but here are photos with and without the screen. You can see why the undersides of the soffits are an easy place to start adding bass absorbers since they wouldn't take up much room. Question is how to make the best use of them.

Ion
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post #4 of 4 Old 06-25-16, 04:17 PM Thread Starter
Shackster
 
Join Date: Oct 2013
Location: Mostly London
Posts: 6
Re: Need to fix room decay time of 1500ms

Maybe I should ask for advice on a different question: what is the best use I can make of the space underneath my soffits? The room has 14' soffits on each side which are 13" wide (pictured). It seems like a waste of good corners for bass absorption not to put anything there.

Any help would be appreciated.
Ion
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