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Corner square bass traps versus full wall bass trap, and air gap versus no gap (front and back walls). Help confirm my decision.

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After reading other posts, room mode simulations here, and flow resistivity estimate here, my assumptions are as follows .

1. Corner bass traps and the idea that "bass builds in the corners" isn't all that accurate. Maybe it's 2 walls next to eachother so one square bass trap partially covers 2 walls at one time. But it isn't better than a full wall "bass trap."

2. Thicker insulation with less density is best for bass trapping. Therefore pink fluffy insulation is better for thicker traps compared to mineral wool.

3. For my space I can utilize 8"-16" on front wall and same on the back wall. I calculate that 8" of insulation with an 8" air gap does similar bass attenuation compared to 16" of insulation (OC pink fluffy insulation with flow resistivity of around 6k-8k).


Therefore, my conclusion is building width/height walls out of insulation for the purpose of bass attenuation is best and I'm better off using OC pink fluffy with an air gap to be most cost effective and best performance within my allowed space. Of course, measure results and make adjustments for my space after measuring.

Am I on the right track?


(Possible follow up question. Would it be better to have both front and back wall 16" bass trapping, or only one wall 32" bass trapping?)
 
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Have you looked into VPR traps? They are pressure as opposed to velocity traps and don't rely on airflow. From what I have seen they can be a very good option, especially for the bottom octaves. DIY is possible at cost comparable to insulation-based treatments.

My understanding is to make one of these, you glue a large sheet of thin steel to a piece of foam, basically. The steel sheet has enough resonant modes, low enough, that it absorbs bass from the air and dissipates it in the foam.

Steel sheets of considerable size aren't that expensive, and then you can use an old mattress topper or something for the foam.

Something I want to try, but haven't got around to yet. There are some threads on gearspace about DIY builds if you want to look into it further.

I don't think you're on the wrong track as far as velocity traps go, but I also think velocity traps are a bit of a dead end for low bass.

You might also want to look into binary amplitude diffusers, which (for reasons I don't fully understand) also seem to improve absorption with thinner panels in the <120hz range. These are also possible to DIY if you have access to a laser cutter, 3d printer, or just have a lot of patience and a drill, to make the facing sheet.
 
Have you looked into VPR traps? They are pressure as opposed to velocity traps and don't rely on airflow. From what I have seen they can be a very good option, especially for the bottom octaves. DIY is possible at cost comparable to insulation-based treatments.

My understanding is to make one of these, you glue a large sheet of thin steel to a piece of foam, basically. The steel sheet has enough resonant modes, low enough, that it absorbs bass from the air and dissipates it in the foam.

Steel sheets of considerable size aren't that expensive, and then you can use an old mattress topper or something for the foam.

Something I want to try, but haven't got around to yet. There are some threads on gearspace about DIY builds if you want to look into it further.

I don't think you're on the wrong track as far as velocity traps go, but I also think velocity traps are a bit of a dead end for low bass.

You might also want to look into binary amplitude diffusers, which (for reasons I don't fully understand) also seem to improve absorption with thinner panels in the <120hz range. These are also possible to DIY if you have access to a laser cutter, 3d printer, or just have a lot of patience and a drill, to make the facing sheet.
Thanks. I've looked into various Helmholtz and other pressure traps. It seems out of my knowledge scope. I may try them in the future depending on budget. For now my goal is to get up and running within the next few weeks with "good enough" sound Using velocity/friction type attenuation.
 
The reality is if the room is smallish and you don’t have like… feet of space for the bass trapping to occupy you won’t do much in the sub 200hz area where the real problems are for most rooms, just do what makes the most sense in the space you have and it’ll be a big improvement over nothing.
 
Thanks. I've looked into various Helmholtz and other pressure traps. It seems out of my knowledge scope. I may try them in the future depending on budget. For now my goal is to get up and running within the next few weeks with "good enough" sound Using velocity/friction type attenuation.
Helmholtz is pretty hard to wrangle in most rooms I think.

VPR is interesting to me because it's literally just a thin steel sheet glued to a piece of foam, which I am sure I could build myself. And, they don't need to be very thick, just cover a larger area. An 8' x 4' steel sheet should not cost you more than the equivalent area of good quality insulation. I think I priced out an 8 x 4 VPR at $150, if I used secondhand bedding for the foam... :D

In some of the gearspace forum threads they show several dB of improvement below 50hz... this is not something I've seen happen with plain old fiberglass. Just saying.
 
Helmholtz is pretty hard to wrangle in most rooms I think.
After seeing https://homeaudio.jimdofree.com/ I'm changing my mind on this somewhat; it's more work to build than a mere plate (would love to see measurements on VPR though, is that available somewhere?), but unless a room is truly tiny, to me it looks like adding resonators to tackle the 2 main room modes doesn't take that much space and would work very well (as in pretty much completely eliminating the room mode). Aesthetically also is ok-ish since it's just a coloured box.
 
After seeing https://homeaudio.jimdofree.com/ I'm changing my mind on this somewhat; it's more work to build than a mere plate (would love to see measurements on VPR though, is that available somewhere?), but unless a room is truly tiny, to me it looks like adding resonators to tackle the 2 main room modes doesn't take that much space and would work very well (as in pretty much completely eliminating the room mode). Aesthetically also is ok-ish since it's just a coloured box.
This thread has some measurements of DIY VPRs... (Sorry, it was stereonet not gear space) It's what got me excited about the category. You can see clear changes even as low as 40hz, which most bass traps struggle with at best. I think they're also fairly easy to build.

https://www.stereonet.com/forums/topic/255894-experience-with-diy-vpr-anyone/page/4/
 
This thread has some measurements of DIY VPRs...
That's pretty impressive. They're not exactly small though. On the other hand they're not very thick so can likely be hidden behind a closet; assuming they still work there.
 
I made a bunch of gigantic bass traps for my room about 10 years ago and honestly they did very little to improve the sound. Buying a second sub and applying proper EQ was much more effective.
 
That's pretty impressive. They're not exactly small though. On the other hand they're not very thick so can likely be hidden behind a closet; assuming they still work there.
Yeah, they need to cover a large area like most treatments, but you can get away with a few inches of depth instead of like, 12-24" to start thinking about slightly affecting those frequency ranges.

I think anywhere you put them that directly communicates with the volume of air in the room should work. So not inside a closed closet, but on the back wall of the closet (if it is open to the room) should work the same as anywhere?
I made a bunch of gigantic bass traps for my room about 10 years ago and honestly they did very little to improve the sound. Buying a second sub and applying proper EQ was much more effective.
+1 for 2 subs and EQ being a good solution. I do this myself in my office. However, they do almost nothing for decay times, which you generally want to shorten to get a bit more clarity.
 
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