Any Opinions On This Wall Detail

Hi Everyone: I am looking to build a rehearsal room/Recording Studio in my Garage (very much like the one studio_drums has built). I have a kids bedroom above and neighbours with different musical tastes to say the least. The size and other details are very similar as well. viewtopic.php?f=2&t=9166 The difference that I have is that the house inside wall is finished and I can't change that, the garage side wall has Roxul insulation in the stud cavities and I haven't yet drywalled it. I'm wondering if I am better to go with the mass/air/mass configuration that is in my first sketch by adding 3 layers of board to the garage wall and then 3 layers to the studio wall or to leave the garage wall insulation exposed and add 6 layers to the inside studio walls. (Note: that I received a stack of unused drywall from a completed jobsite that didn't want it any more so I have about 6 layers worth total for mass). Also is it worthwhile in your opinion to add a 90 lb. layer or roofing membrane (rubberized type approx 3/16" thick) between the two layers of drywall. Thanks in advance. I am waiting for the highly recommended Home Recording Studio: Build It like the Pros book that I ordered this morning but I don't know if the second configuration would be discussed in it...or am I just :horse:[

the second pic is best. m-a-m. (wow, that was short... yeah, sorry)

I agree with Ro. But.... The way you are setting up your mass is going to leave you open to sound because the exterior or neighbor side is pretty thin. How easy would it be, for you, to cut pieces of drywall to fit in between the studs on that wall? You would be able to mass up the exterior side to the same amount as the interior(studio) side plus distribute the load. Just something to look into.

Great Idea. It would be so easy its almost ridiculous. The side against the interior of the house has Roxul between the studs and and the outside has nothing (Shiplap and Hardie plank with an empty stud cavity). I've got my material and the build starts tomorrow! Your idea will be incorporated into the room. I am going to glue 2 layers to the house side c/w acoustic caulking the joint between the stud and each layer of infill drywall then replace the Roxul. Same but using screws to the outside part :yahoo: Any ideas for holding the roxul in place as there will be no board at the "air" side between the walls . I was thinking of trying to find some of that plastic woven banding that they bundle pallets together with and stapling it to the studs. The concern is actually with the roxul exposed in the garage ceiling because my son's room is above and I'm worried that his jumping around will eventually loosen the insulation which is friction fit between the joists. Thanks