local lumber supply has it and only $35 per sheetI like the 3 layers of baffle for the front, i did that myself....but realistically you are over building this...2 layers everywhere else plus all that bracing? I think you could get by fine without doubling the other walls.
where are you finding 1" baltic birch in 4x8 sheets? I have only found it in 3/4" 5'x5' sheets.
Probably overbuilt, but why worry? I'm not sure I've seen anyone take a cabinet to that extreme, so you can be the pioneer. There's no down side to an inert cabinet (other then the weight), and you can pretty much guarantee that one will be inert. How many watts are you going to through at it? What size is your room?its all 1" birch and im overbuilding this?
If there are no physical boundaries between your living room and the other rooms then the sub will "see" them all and try to pressurize the entire space. Depending upon where you're seated, relative to the subwoofer, you may find a single 15" acoustic suspension design won't be sufficient.Well my living room is open to my dining room ans kitchen but my actual living room is around 16 x 13 and it will have 1000w going to it