I'm planning to soundproof my theater (room within a room).How do I mount a projector on the ceiling, sturdily, without compromising the soundproofing?

Maybe I'm totally off the mark here but I think you would have to try pretty hard to install a projector in such a way that compromises any treatments you've done to the room. Isn't it just a matter of drilling a few holes?

yea, I think your biggest worry would be mechanically compromising the setup with a misplaced screw. I wouldn't sweat it. How big of a PJ are you using? If you aren't using a 70 pounder, you have lots of options. I'm sure it's been covered in one of the PJ forums.

If you're building a true room in a room, you'll have your own ceiling joists separate from the ones on the floor above. Just triple up the center one to support the extra weight and give yourself a nice place to mount it without tying it to the outer structure.

When you bolt it up, pre-drill the holes, fill with caulk, and tighten the screws.

Bryan

How many layers of drywall/board are you using and what centres are you mounting your joists on. I did the joists at 12" ctc, with 2 layers of 5/8" drywall with a layer of 3/4" solid MDF sandwiched in the middle. I did this on all the walls and ceilings and besides the isolation benefits I can mount anything anywhere, anytime. The strength comes with size of your joists (2" x 12") and the span they run. Pre-drilling holes is key with MDF.
Don't forget to pre-install empty conduit tubing (ceiling, walls, floors) to get wiring from the back/front/sides of your room, to/from projector, speakers etc.

Thanks for the responses. I think the two layers of sheetrock with the MDF will be more than adequate.