Flat ceilings vs. Shed shaped -Acoustics Forum-Acoustic Fields Forum

I have seen at the end of a few of the Acoustic Fields videos that in the background image it shows a room with a three surface shed shape ceiling. Is that something that is okay for a dedicated A/V room. I am designing a new house with a dedicated room. 13 ft. high x 21 ft. wide x 33 ft, 9 in. This is as big as I can go in the house plan. The only thing is the one story house has an outer wall height of 10 feet and vaulted ceilings with a 12 – 4 pitch. This means I can have a A/V room with a three surface shed shape or flat if I sink the floor and have steps going down in the room. Which is best or can the rooms be treated to perform the same way without a significant difference in cost?