Rob,
> The bottom is one big open room (with iso closet) 26' x 19' x 9' <
Nice size.
> I am building a room within a room and angling walls. <
Do you really need to do that for isolation?
> I want to have a mason build a 1/2 or 3/4 height stone wall wrapping around one of the corners as an ambience area. Will this work or is my room just to small? <
That sounds like a great idea.
> I plan on using minitraps but am wondering about diffusers. Floor will be hardwood. Please advise. <
Diffusion is useful in a large room like yours. But good diffusors are not cheap.
--Ethan