In-wall speakers and room-in-room constructions

Once again, sorry for straying into the studio domain, but somehow it seems that the sound insulation expertise is hanging here... I'm building a home theater in my basement and try as good as I can to make it well sound insulated. This means room-in-room, gypsum+ GG + gypsum + GG + gypsum on ceiling/walls, double sound insulated doors etc. etc. Now, I'm considering in-wall surround speakers and what I'm trying to figure out is how bad this is for the sound insulation, punching through the walls like this. Before yelling, please look at the sketch below (seen from above). My plan is to add the same amount of layers behind/between the studs as the rest of the wall. The surround speakers, as you may know, will be high passed at more or less 80Hz. So the worst bass (problematic frequencies sound insulation wise) will come from other speakers. I don't expect anyone to actually have tested this, but theoretically - how bad is this solution? :oops:

i think it looks ok you still have your 2 leafs. but dont hold me to it. joey

Theoretically it looks quite good. If I was in the same situation as you are, I would do the same thing. Andre

in your image, we're looking from above at a speaker enclosure. In the back of the enclosure you have layers of wall board. On the sides of the enclosure, the drawing just shows framing - as if we're looking at the header of your framework around the enclosure. Wouldn't the same layers of wall board have to be on all 5 sides of the box? Also think about what you're going to do with placing the speaker within this hole - are you going to try to buffer the contact with the speaker and the speaker enclosure? Some people have gone as far as making an enclosure that goes all the way from the speaker location to the floor. They basically have tubes of cement (mass) sitting on pucks/pads that the speakers would rest upon. Then creating a false or true front to house the concrete tube. good luck. those are a couple things I noticed while poking around this site for the last year.

Cram wrote:

in your image, we're looking from above at a speaker enclosure. In the back of the enclosure you have layers of wall board. On the sides of the enclosure, the drawing just shows framing - as if we're looking at the header of your framework around the enclosure. Wouldn't the same layers of wall board have to be on all 5 sides of the box?

I don't know. Maybe? What effect would these layers on the sides (in addition to the studs) have? Adding weight? If that's the goal I'd rather haven them on the outside, because the speaker enclosure volume is limited as it is.

Cram wrote:

Also think about what you're going to do with placing the speaker within this hole - are you going to try to buffer the contact with the speaker and the speaker enclosure?

I'm not entirely sure what you mean by "buffer" in this context. Do you mean some kind of mechanical insulation, some kind of soft gasket?

Cram wrote:

Some people have gone as far as making an enclosure that goes all the way from the speaker location to the floor. They basically have tubes of cement (mass) sitting on pucks/pads that the speakers would rest upon. Then creating a false or true front to house the concrete tube. good luck. those are a couple things I noticed while poking around this site for the last year.

Thanks a lot for the info, Cram! And thanks to you two other guys as well! (I've added a little to the sketch, just to clarify...)

RuneW wrote:

I don't know. Maybe? What effect would these layers on the sides (in addition to the studs) have? Adding weight? If that's the goal I'd rather haven them on the outside, because the speaker enclosure volume is limited as it is.

I'm pretty sure that would be a hole in your first leaf/mass of the Mass Air Mass design. essentially, the two layers sitting behind the speaker are there for reflective purposes. There is no mass on the sides to make it a true enclosure and layer of mass. I may be mis interpreting what you are designing, but I think that's a hole in the design.

RuneW wrote:

I'm not entirely sure what you mean by "buffer" in this context. Do you mean some kind of mechanical insulation, some kind of soft gasket?

I assumed without you drawing the speaker that a speaker BOX would be sitting within that enclosure. I think from your replied drawing that you're planning on having it sitting on the wall. What I mean by a buffer is that the vibrations are buffered from the speaker to the wall/leaf.

Cram wrote:

RuneW wrote:

I don't know. Maybe? What effect would these layers on the sides (in addition to the studs) have? Adding weight? If that's the goal I'd rather haven them on the outside, because the speaker enclosure volume is limited as it is.

I'm pretty sure that would be a hole in your first leaf/mass of the Mass Air Mass design. essentially, the two layers sitting behind the speaker are there for reflective purposes. There is no mass on the sides to make it a true enclosure and layer of mass. I may be mis interpreting what you are designing, but I think that's a hole in the design.

Or I may not know what I'm doing at all... So what you're saying is that you wouldn't consider the stud as a leaf? Maybe it isn't. I'm not in any way a "leaf expert", so please bear with me, but why wouldn't you consider this a leaf?

Cram wrote:

I assumed without you drawing the speaker that a speaker BOX would be sitting within that enclosure. I think from your replied drawing that you're planning on having it sitting on the wall. What I mean by a buffer is that the vibrations are buffered from the speaker to the wall/leaf.

It's not yet decided whether I'm going for a speaker with it's own enclosure or one without (or indeed if I'm going in-wall at all). Of course, going for one without will necessarily be the worst solution, and would generate it's own vibrations on the wall, no matter what you do. My hope was that, since they're high-passed, that the most troublesome frequencies (lower bass) was not made by these speakers at all.

I wouldn't do it. I would not retro fit speakers into this thing. What if your placement is off? What if you buy bigger better speakers next year? You have gone a long way to ensure isolation and the surest way to compromise that is to cut into it. I'd look into Crams idea first. But it is your wall.

HAH! Found an example of what I mentioned - http://www.johnlsayers.com/phpBB2/viewt ... &start=120 Find len's post near the bottom on the speaker stand he makes. You'll see that it's within the wall and he's got a concrete (cinder filled with concrete) pillar. This one isn't decoupled from the floor, but it's the same idea. That peice is in the wall. I'd also consider what xSpace said with regard to the Perminent nature of a speaker housing. Your question about the studs not being mass - Only wall board or something as dense as wallboard (mdf, concrete) is going to qualify as MASS. The framing of a structure is resonant or more resonant. Hell wood's born to vibrate. IF you were going to go the route of your drawing starts with, I'd have the entire inner housing fitted with one or more layers of wallboard and the wire would have to be caulked in nice and snug to stop any air gaps. I hope all this is a help to you. There's another fine example of one of those platforms, but it's on an older build thread and I cannot find it just yet.

Heres a Sketchup that Glenn (gullfo) did for a block de coupled monitor stand: http://www.johnlsayers.com/phpBB2/viewtopic.php?t=10021

Thanks guys! You have convinced me not to go the in-wall route at all. Risc of reduced sound insulation and limited upgrade options are two very good reasons to drop this idea!