hi, my room was very boomy and had standing wave problems. i put michael greene room tune pillows in the 4 upper corners and 4 24x 24 inch cathedral panels[absorption] on the rear wall. problem solved for my room. due to having magnepans i put diffusion on the wall behind the speakers. with conventional cabinet speakers i put absortion behind the speakers. there are lots of sites for information. aurelex has one as do many others. you could also build some. good luck. my room is 14 x 22 feet