3 and 4 -leaf question

I'm building up my 15'X25'X9' studio....actually have the walls framed now. However I have a question about 3 leaf construction. Most of the walls in my studio are double walls framed on seperate 2X4 base plates and will have double drywall on the outsides and rockwool insulation in between. However, my studio room is adjacent to a set of stairs, and I intend on having an amp closet in the area underneath the stairs. Please see the attached sketch...I can provide photos too. The problem that I'm facing is that in order to have some isolation of my amp closet from the rest of the house (it doesn't have to be high STC or TL here as the closet will not often be used) is that I need to put two layers of drywall underneath the stairs, and I intend on stuffing the cavity with insulation. The problem is that the area surrounding the door will also have drywall on both sides, and if you consider the transmission path from the main room up the stair through the closet area it's either a 3 leaf problem or a 4 leaf problem depending on which wethe the sound gets into the closet via the door (3 leaf) or side wall (4 leaf). My question though is this....is this really a 3 or 4 leaf issue, or is it more like an airlock, given that there is several feet (3 or 4 anyways) seperating the leaves? Cheers, Kris

drfrankencopter wrote:

is this really a 3 or 4 leaf issue, or is it more like an airlock, given that there is several feet (3 or 4 anyways) seperating the leaves?

Perhaps this thread -- specifically, Rod's response at the end -- will answer your question. :) Or confuse you further. ;)

Nahh, not confused.....it's not a 3/ or 4 leaf system because there is sufficient air between the leaves. Similar to the hallway issue Rod mentioned. Phew! K

Man that's a great 3D shot. I would actually paypal someone some $$ to quickly do one of those for me from my plans if I actually had some that were not all in my head!! JG

Guys, before you get TOO ecstatic about 3-4 feet making things NOT multi-leaf, I was told some time ago by Eric Desart that to completely eliminate the multi-leaf effect it would take quite a bit of distance - more like a wavelength or more (which is about 32 feet at a 5-string bass' low B) - about that same time, I posed a question (with pix) to Eric, Rod, John and Wes Lachot, and got basically the same answers from each which I sum up in this post (sorta) However, in the case of air locks everyone agrees that the closer problem should get the priority; IOW, with airlocks if anyone will be playing or recording when the air lock door is opened, then EACH wall of the airlock needs to be double leaf; this automagically makes the total airlock a quad leaf situation when all doors are closed, but it can't be helped so we beef up things by adding more mass and live with it. For an amp closet, you should figure out ALL sound paths and decide which is the most important one to isolate the most, and go from there... Steve