pigmode: the back wall is the one with the bay window. i know this is backwards to the recommended way. since the sond waves are directed together by the slanting walls. but if i put my stereo equipment there, i wouldn't be able to see out. using the tube traps is very fun, since one can change the sound so much. it seems that any movement makes a difference in the sound. most of the traps are made with fiberglass tubes made to insulate pipes. they range from 16 inches to eight inches, i think.