# No impact from these Bass Traps - why?



## drwho099 (Oct 8, 2014)

I’m looking for advice regarding my bass traps. Recently I upgraded to dual subs (15” PSA S1500’s, placed near mid-side walls), and decided to finally tackle the room treatments to reduce bass boominess. Room is a dedicated sealed theater room with dimensions 22Lx15.5Wx10H, and was only lightly treated before with only side-panel first reflection absorbers. Pictures of the front and rear of the room are attached at the end of the post. Walls are drywall and floor is carpeted. 

Anyway, I created/installed DIY superchunk bass-traps in each of the front corners, the traps being 15x15x22 made from Roxul SNS, spanning almost but not quite floor to ceiling. Prior to installing the traps, I measured levels in the front corners using my portable analog soundmeter, and found those corners to be 2-3dB hotter than other parts of the room. Treating the rear area is more problematic due to bookshelves, and those areas did not measure as hot anyway. 

I did not expect a lot from the traps given their relatively small size, but expected something in the way of reduced decay time. But I see (measure) basically zero benefit from the traps. Before and after measurements are below (REW w/UMIK1 calibrated mic, unsmoothed). 

Any suggestions as to why I saw no benefit, and whether there’s some additional tweaks to the DIY traps that would improve the performance?

AFTER MEASUREMENT (labels on graphs are swapped).








BEFORE MEASUREMENT (labels on graphs are swapped).








I was thinking of adding a 1” panel of denser material (OC703?) in front of the existing chunks, but am not convinced that would have much impact. For grins, I placed a bat of an unused SNS roll on one side and measured – again with no change (admittedly, that only covered ¼ of the trap’s area (picture below) – but was an easy test to do).

Room shots:
















Quick test with additional SNS up front as shown (no measured change):








Thanks,
George


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## bpape (Sep 14, 2006)

Getting below 50hz is going to take a lot more thickness. Our Soffit Trap which is 17x17 square will get down into the mid 30's.


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## drwho099 (Oct 8, 2014)

Yeah - understand that, but what I could not quite understand is why there was no impact from the traps even above 50hz.


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## NBPk402 (Feb 21, 2012)

drwho099 said:


> Yeah - understand that, but what I could not quite understand is why there was no impact from the traps even above 50hz.


Maybe you don't have enough of them?


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## bpape (Sep 14, 2006)

you sure you don't have those pics labeled wrong? Looks like the pre has shorter tails below 100 than the post


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## drwho099 (Oct 8, 2014)

Shoot - I rechecked the original mdat file and its timestamps, and you're right - they are labeled incorrectly (swapped pre for post actuals). 
In my defense the difference still seems quite small. (I'll edit the posting shortly to correct.)


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## bpape (Sep 14, 2006)

Well, it did shorten the decay from 50-100 Hz which is about what I would expect but not lower.


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