# some questions on bass traps



## ToBeFrank (Feb 27, 2010)

I've started the process of adding treatments to my living room to improve the acoustics for HT. I'm starting with the 2 back corners in my room. I only have 2 corners because what would be one of the front corners is an angled wall with a fireplace and what would be the other front corner is a 100 sq ft opening.

I picked up some 2" thick 2'x4' 8 pcf mineral wool board. I've read that less dense than that is better for the bass traps, but this is what I can get locally that doesn't cost an arm and a leg. Since this material is almost 3x denser than 703, I'm wondering if I should do super chunks or just panels in the corners? I don't know if I will be wasting material by doing super chunks.

I did some testing by temporarily setting the panels in the corners. I first did 2 panels (4" depth), then 3 panels (6" depth). The difference in the waterfall graphs and RT60 time between untreated and 4" is significant above 60Hz. The difference between 4" and 6" is slight (if at all). I don't see much difference with either below 60Hz. Will doing superchunks versus the panels make some improvement below 60Hz? Also, how important is it to get the traps all the way to the ceiling? I only bought 4 bundles so far and my ceiling is 10ft so I have a 2 foot space at the top of both corners right now.

EDIT: I'm using a Radio Shack analog SPL meter.

Below are the REW graphs:

Before:









4":









6":









RT60 (red=before, blue=4", green=6"):


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## bpape (Sep 14, 2006)

You're getting there with the 6". Chunks are the same amount of material as 6" straddling and will work as well or better and take up less space. Just understand that not all problems are corner related in terms of frequency response.

Bryan


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## ToBeFrank (Feb 27, 2010)

bpape said:


> You're getting there with the 6". Chunks are the same amount of material as 6" straddling and will work as well or better and take up less space. Just understand that not all problems are corner related in terms of frequency response.


Thanks Bryan. Will 24" hypotenuse super chunks be sufficient for the low frequencies? I was under the impression I'd have to do 34" hypotenuse to get them. The reason I was thinking about panels is 34" super chunks for 2 corners and a 10' ceiling takes 30 sheets. With the 4 bundles I have now I currently don't have enough.

I understand that not just the corners need treatment. If I can do 24" super chunks it will take 15 sheets to cover the 2 corners. That still leaves me 9 sheets to make panels for my walls.


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## bpape (Sep 14, 2006)

The 34" will reach deeper certainly. From a decay perspective, you're already pretty decent down into the 30's. You're down about 55db or so after 400ms. 

Bryan


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