Heres a crappy draw-up of the garage to give you an idea of what I have. I put the studio area on there plus I wanted to show you how the rafters run. They are 2x6x13. They sit on top of the concrete block and connect to the roof joists. Do you think these are strong enough to hold the drywall? Maybe I can double them up to get a higher ceiling. Let me know if there is anything you need me to show in this pic. Thanks guys.
i think the existing 2x6 might be on the margin for supporting the new weight. one thought - build the new inner walls about 2" lower than the joists and rest a new set of 2x10 joists in-between them (say 26"oc) on the inner walls, and build your inner ceiling on that.
since its a square room i'd use slat resonators across the corners to break up the angles and do some absorption. i'd make those 8' high, then use the last foot or so to put up some big clouds. for the floor - if you don't float it - i'd polish and stain the concrete, then build a drum riser to get the kit off the floor.