Besides 6" Panels for side walls, back wall and ceiling, I'm also building Soffit Bass Traps for the 4 Corners (Floor to Ceiling) as well as Front/Rear and Side Wall/Ceiling Corners for my Home Studio.
The 4 Main Corners are good (17" x 17" x 48")
My challenges are with the Side Wall Ceiling Corners.
On 1 side I have a window and the other side an in-built closet, Both with a frame approx. 1/2" thick and 13 1/2" from the Ceiling.
My questions are:
1) Do I make 17" x 17" Soffits and leave a gap to clear the frames or do I make
them 13 1/2" x 17" and have them against the wall?
2) In general, what are the Pros/Cons for leaving small gaps behind any of these
Bass Traps (ie; Absorption effectiveness as well as Air circulation and any
other possible concerns)?
P.s. Traps are not been built as permanent into walls. Will probably use Angle Brackets to Install.
Thank you to all in advance for your advice and Input,
Hey, mrfye; welcome. So, I don't have soffits but I do have rigid panels and 31x47x24" fluffy 'super chunks'. They seem to behave the same way when gapped in that you get extended effectiveness to a lower frequency but it comes at a cost. Gapping, in my experience, creates a sort of imbalance in how the absorber works. Some will tell you that there's a slight dip in absorption in the low mids. In practice, you'll start getting weird SPL and decay responses. While the best thing you can do is to experiment with gap distances then measure and compare your results, the rule-of-thumb I'll share is that you want to be somewhere between flush-mounted and a 2x gap. Your room may differ, and I do have many of my rigid panels fluctuating around this threshold via angling, but trying to 4x gap an absorber is just doing it wrong unless you have a specific frequency range you want to effect and for some reason you don't have the appropriate thickness of absorber.
I'll chime in regarding the gap. The reason to use a gap AT ALL is to increase the LF performance of the absorber. In theory, if you have a 6" panel flush with the wall, it will perform at 100% at about 500Hz (and a lesser % as the Freq goes lower). If you double the thickness to 12", your panel will do 100% at about 250Hz and so on as you go thicker. The idea with using a gap is that you can effectively double thickness of a panel by simply spacing any distance off the wall. If you take a 6" panel and space it 6" away from the wall, it will perform almost as good as a 12" thick panel. (BTW, you can use any panel thickness, just use the proportion of the space relative the given panel).
Now, you can take this idea to extremes and it WILL WORK for the lowest frequency: Say you spaced a 6" panel 18" off the wall. OK, that's an effective panel 24" thick, cool. So now you'll be at almost 100% at 125Hz. The thing is that some of the freqs between 500 (the 6" panel alone)and the 24" thick "virtual panel" may not be absorbed as much as if there were a real 24" thick panel.
BTW, I pulled the freqs in the above example form a chart of 1/4 wavelength so they are just approximations and not from measurements or real world examples. There are other factors in play but I this is the general idea
If I may, I think what Hexspa is saying is, keep the gap the less than 2 times the thickness of the panel thickness. But if that's the case, even that might be taking it a little to far. I think a gap equal to the panel thickness will insure you don't end up with less absorption "holes".
Now in the case of corner traps, the space behind the panel varies from 0 at the edges to 12" in the middle. Even though this leaves "holes" in the absorption freqs, they seem to average out to yield a pretty good bass trap. Filling the space completely IS better (the SUPER CHUNK) but when you consider the cost of materials, the "panel across the corner" is a competitive alternate.