building angled walls

gravikords Hey now! Great site! I've been reading many of the posts for a couple of months now, ever since I've deceided to build a studio and I think I'm getting the basic idea. (that may be my first mistake)... anyways there is one burning question that may be very well obvious but I still can't figure it out! ....if I'm building two seperate walls, then creating a wall that is at angle, ei. 15 degrees (acting as a third wall??) what then is that angled wall covered with?? The reason I ask this is because I believe that I read here that you wouldn't want three walls covered with drywall. Now is this wall covered w/ rigid foam/ slat resonator/ traps ect and NO wallboard ?? Forgive my confusion, just need to know before I start. Thanks ever-so-much.[outzone recording][/list]

Greetings and welcome! The third, interior wall would pretty much be a false wall. The "3-leaf" wall system you're trying to avoid would only happen if you covered that interior wall with drywall and sealed it tightly. When we build false walls, they're usually just rigid fiberglass insulation with fabric covering, and perhaps wood slats as you mentioned. You could build slat resonators into the walls like this if you wanted, but even just having an angled wall with fiberglass blanket insulation in it would do a lot to soak up low frequency sound- the false wall would space the insulation away from the hard drywall wall on the other side. And if there's enough space behind the false wall, you could install hangers to absorb even more low freqs. There's lots you could do with those walls- just don't seal 'em. Your hunch was correct.

Thanks! What a wonderful source of information and inspiration that all of you good people provide at this site! Perhaps it's partly because I live in a cave, but to me it's something to behold! :D

Anybody have a good source for (reasonably priced) acoustic caulk??

I started out buying the expensive caulk - the $10 a tube stuff. Then eventually after some investigation realized the expensive stuff is all smoke and mirrors. HD / Lowes have some cheap stuff that is thick - $1.50 a tube - it works fine - remains flexible and doesn't crack. Believe me you will use a lot of this stuff. I'm guessing I have spent well over $500 on caulk. If you opt for the expensive stuff you will pay a lot more for no benefit.

I don't know where you're located, but I've been buying it here in Nashville for $3.25 a tube if I buy it by the case (12 - 29 oz tubes). There are different MFG's. Boss, Grabber, Titebond, etc., etc... They usually refer to it as "Acoustical Sealant". And Andrew's right, you'll use a bunch of it. I'm on my 3rd case now. Aaron

Thanks guys, I almost ordered 20 tube for 150.00$ last night, glad I asked! :D

When we build false walls, they're usually just rigid fiberglass insulation with fabric covering, and perhaps wood slats as you mentioned.

Hello Kase, can you explain what the purpose of the slats would be, if you can't seal the backside of the "false wall", since slat absorbers, from my understanding, are hemholz resonators, and must be sealed to work, no? And one more thing, couldn't you sheetrock the backside of this wall, and seal it as one leaf of a 2 leaf 2 wall system? Wouldn't this simply be a "inside out" one leaf wall? fitZ

Rick, you could of course do it that way - but there are a few reasons NOT to, if you can afford the room and extra materials - first, any trapping/absorption that's done as part of a wall tends to weaken the isolation of the wall at the trapped frequencies - (it's gotta go somewhere) and designing a wall is basically the same as designing a bass trap - it's all about mass-air-mass resonance. For best isolation, you want a m-a-m resonance that's at least an octave lower than the lowest note you want to stop - this takes quite a bit of mass to accomplish. If the inner leaf of your isolation system is also trying to be a bass trap, it (by definition) has to let some bass through (counter-productive to good isolation) - So, generally if you can it's best to over-build your isolation system (mass-air-mass barrier) for better isolation than you think you'll need, then do your acoustic treatment as a third (non-hermetic) inner shell. This can make the room into an RFZ by using splayed sections, it can hide bass hangers, parts of it can be made into slat resonators, diffusors, etc, depending on placement and size of the room - and, by over-building the isolation part (the two outer leaves) you compensate for the losses in isolation that traps create. And yes, Helmholtz traps need to be sealed - but that seal can be the inner leaf of the isolation shell, and the air gap can be variable - the general concensus is that a splayed slat resonator without individual septums between slots would tend to average out according to the median depth, with possibly some broadening of the response peak caused by the varying depth. Personally, I think I'd put separators in about every 4 or 5 slats if the air cavity was tapered - that way, I'd get more than one "average depth" and a wider band trap effect. There's a discussion on the acoustics forum about this part, it's pretty old - don't remember the title, though, I'm lucky to remember my name at this point in time (12 12-hour night shifts in a row, finally escaped the zoo for a few days, yuchh) Speaking of Slat resonators, I've been working on a new upgrade for the SAE slat calculator - this one's in inches, and also calculates the actual Sabins of absorption to expect at resonance, based on overall size of the trap and the slat/slot ratio - should have it posted for download in a day or two. Hope that answered things, already forgot the freakin' question (where's that damned "wet cat drug through a knot-hole backward" emoticon when ya really need it??!?) Later... Steve

where's that damned "wet cat drug through a knot-hole backward" emoticon when ya really need it??!?) Later... Steve

Hello ya over worked ole fart :) When are you going to take some hard earned time off? I know what your thinkin though..., "what the heck is time off,:shock:?".... right? You deserve a month off Steve! 12 continuous days of 12 hour Night shifts is CRIMINAL I tell ya.....although I bet some new fangled toys are part of the reward huh?. Just don't work yourself to death before you get to use them.....I mean you got RESPONSIBILITY HERE SON!! What would we do......I mean WE NEED YA BUDDY!!:D Well, ok Steve, now I get it. I was under the impression this "false wall", IF SEALED, would be become a third leaf. But, I guess you build it so sound can flank AROUND it, whereby the airgap between the back of the false wall and the inner leaf of the M-A-M assembly, is NOT sealed, is that correct? IF it is, then NOW I GET IT. Hmmmm....NO WONDER.....it's just a bass trap fastened to the floor and ceiling with an airgap behind it, and not sealed on the ends, or one end, or leaks at top and bottom or... ..ok...ok nevermind, then..back to the drawing board :lol: Hey....now that I think about it........WHY does it even have to have an airgap behind it? Ethans don't. Now I AM confused.......again, oh nevermind. I think my wife is right. I'm just a hardheaded old fart. Thanks a mill Steve. fitZ:P