I'm working on a complete treatment of my 20' by 14' by 9' listening room. What I'm considering is using realtraps or similar mounted directly to the ceiling all the way around the perimeter of the ceiling as a kind of soffit. Yes, I know, it's much better to space them but I have tall, narrow windows whose moldings come close to the ceiling, making it aesthetically problematic to angle them across the ceiling/wall junction.
The center area of the ceiling would be treated with RPG HemiFussors. Mondo traps or similar would straddle the vertical corners. RPG BAD diffusion panels and more realtraps would be used to treat first reflections and flutter echoes. There are 9 windows around the room, about 22" by 6' tall, which will be treated with Hunter-Douglas honeycomb shades. Floor is carpeted.
My primary worry with this plan is that I will have too much HF absorption, making the room too dead. Does anyone have experience with over-trapping a room, and how much of the surface area has to be trapped before you get there?