My dad was concerned about hanging all the weight from the ceiling, because he's a worrier. He wanted me to go ahead and frame in the soffit, or at least set a ledger board and anchor it carefully to the joists before I get all the drywall in the middle and have trouble finding firm places to screw into. I see his concern, but I didn't let it change my plans. In any case, it got us talking about how big the soffit will need to be. This is where I'd like some feedback.
The purpose of the right side soffit is four-fold. First, it must encase the plumbing as well as possible to stop water draining sounds. Second, it must encase the HVAC duct that will bring cold air to the front right of the theater (a similar duct will also run to the front left). Third, it will provide a raceway for both wiring for the lights (not the lights themselves) and the speakers and other LV signals. Fourth. it will integrate with other design features that have not yet been decided - moldings, speakers, columns, etc. Keeping all those uses in mind, I'd like to make them as small as possible.
The major challenge to the size is clearly the point where the HVAC duct needs to pass this junction in the pipes.
I'm sure it's hard to make out, but the bottom of the lowest drain pipe is about 10" below the ceiling at this point. Of course, that dimension will change by 5/8" when the second layer of drywall goes up. The pipes protrude out into the room about 14 inches, and that dimension will change by 1 1/4". So with an obstruction 9.5" tall and 13" wide, where would you run the duct? The duct is insulated 6" flex, which looks to me to be about 8" OD uncompressed. Keep in mind the overall dimensions of the room - 9 feet high, minus 14 inches for riser, and only 12 feet wide. The soffit will already be 81" (6' 9") above the riser, so I'd prefer not to loose that much height. But with the room only 12' wide, 1.5 feet wide soffits take up 25% of the ceiling.
Maybe I need to draw it up. But I need to float an idea first. 6" flex could be adapted down to a smaller rigid duct for a foot or two as it passes the plumbing, couldn't it? what size would you use - maybe 9x3?, or would you not consider it?