[Zeke]

If the return air is in the hall, how does the air from the home theater exit? I see a lot of homes where the door to a room is too low to the floor to allow air to move under. That's usually the only path back to the return register. Door open, no problem, but if the door remains closed most of the time, no circulation.

If noise or privacy are concerns for any given room and the door is cut to just skim the carpet, you must install a transfer duct or through wall pair of registers to allow free circulation. I can't tell you how many doors I have cut to allow an inch above the carpet or hard flooring.

Look at it this way, if the register is a 6 x 12 on a 6" duct. that's nearly 30 sq in for the duct and 72 for the register. A 30" door with a one inch gap at the bottom ='s 30 sq in.

If it's an 8" duct (not likely unless it's a large room), that's 50 sq in trying to leave under a 30 sq in the under-door condition. Won't flow correctly w/o an additional return area.

I can say in general that all doors in a home need to have about an inch of clearance. First thing I look at when folks complain of temperature imbalance.