I honestly have one of the worst acoustic environments you could have in my room...10 guitars hanging on a single wall. There's a futon, curtains and such, but nothing that really reduces flutter and echo. Terribly for trying to record trumpet, loud guitar, really, anything. Anyways, so I've got an empty closet in here. I've been contemplating a design based on the room within a room concept, on a small scale. VERY small scale lol. My final planned dimensions for the exterior (LxWxH) are 52"x53"x80". The walls will be 4 inchs thick, 1 inch MDF-2 inchs of board fiberglass insulation, and another 1 inch of MDF. I've been planning on putting in a window, but who knows. The door will be attached to only one of the sides, interior v. exterior. I don't know how feasible this is, but I think it's an interesting plan, no? I can't think of any other way to decouple on the cheap, other than this. I hope that the compression of the insulation will be enough to make it seems stable inside. Any thoughts? I'm not an acoustic engineer or anything, far from it really. Just tired of recording under a blanket. Cheers!