# DIY Corner bass trap density question



## guild (Mar 21, 2013)

Hi, I've got back to doing some more treatment to my listening room and am trialling some DIY corner bass traps.

The dimensions are 300cm x 300cm x 415cm and 1000cm high giving them a volume of 0.045 cubic meters
or imperial
1ft x 1ft x 1.5ft approx. and 3ft high with a volume of 1.5 cubic feet

I'm using Earthwool E4332 R2.5 90mm Acoustic Batts cut into 300 x 300 x 415 slabs and stacking them on top of each other. 

I'm wondering how compressed I should make the 'stack'? 

In another thread where the OP was using the white fluffy stuff, the suggested maximum density was 3 pounds per cubic foot but his boxes were much bigger at 10 cubic feet and obviously I'm using different material for the packing.

Any advice will greatly appreciated.
Cheers,
Mick


----------



## bpape (Sep 14, 2006)

At those dimensions, I would definitely compress them some. If my math is correct, compressing to 3lb/cu ft would be about 5x or 5000mm to make a 1000mm trap. 3lb would be about right.

Bryan


----------



## guild (Mar 21, 2013)

Thanks Bryan, I'll finish getting them together and in place and post up some before and after measurements.
Cheers,
Mick


----------



## guild (Mar 21, 2013)

Here is the measurement and waterfall charts post the corner trap installations. How does it look?

















I haven't been able to find the before measurements for comparison... not sure what's happened but I'll post them as soon as I sort them.
Cheers,
Mick


----------



## bpape (Sep 14, 2006)

Scroll up the waterfall so the left scale is showing the last number at the bottom at 35 please.


----------



## guild (Mar 21, 2013)

Here you go...


----------



## bpape (Sep 14, 2006)

Got a few small tails up in the 70-100Hz range which are probably something in the room resonating as opposed to the room itself. Pretty far down in level though. More intense tails lower down, looking at the slopes again likely more of the same thing but more noticeable. Probably worth walking around with those frequencies playing to try to identify them. Can be things like lighting fixtures, glass, etc.

Down at 30 looks like more of a traveling wave but it's so low in frequency it will be really hard to deal with.

I would be looking to identify what the cause of the sharp 100Hz dip is. Where is the xover point to your sub? If at or around 100, try reversing the phase on the sub.


----------



## guild (Mar 21, 2013)

Thanks for your info Bryan. The room is my listening/control room so no sub, just a pair of Alesis Monitor One MkII's. I spent some time removing my acoustic guitars (the source of some of the resonance) and playing with my speaker positions, forward and back and up and down. Found a position forward of and lower than my original with a 1m equilateral triangle formed between the speakers and the listening position/measurement mic.

Here is what I got:









and the waterfall:









I think the measurement curve is better but I'm not sure the waterfall is improved.
Any thoughts?

Cheers,
Mick


----------



## bpape (Sep 14, 2006)

Lower is smoother but still generally down from mids and highs. The time scale on the left is different than your first plot but still showing tails from 100 down that should be addressed.


----------

