If you have a home depot around When you get ready to insulate the walls and ceilings, they carry cellulose blowing material. I use that in our business here for superior sound control. It is far better than fiberglass due to the shear density of the material.

When you purchase the bags you can rent the blower for around $30 a day. just go ahead and drywall but leave a 2 inch strip off around the walls and stick the hose down in there, and fill it till it is packed pretty good. Then on the top, place the pressure blocks right down the middle and leave a 1 foot strip of the plywood decking off down the center, and blow both directions until it is filled and screw the center strip on and you got a very well insulated box. You can also buy a special drywall called quiet rock, that deadens sound transfer through it.

buy some simple semi rigid fiberglass panels from a good building supply and cover then with fabric, and attach them to the walls like decoration panels , and that makes a great home made bass trap.

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