The living rooms (my main listening rooms) in both my previous house and my current house have very high ceilings - 16 feet. I did not have a ceiling echo in either room. The current room is 24 x 14 with speakers on the long wall. All hard surfaces with parallel walls, ceilings, and floors and no treatments - not even an area rug. If I were you, I would speak to a couple of manufacturers such as Sean from Zu and Duke from Audiokinesis.
