A listening room big enough for my pair of Magneplanar Tympani T-IVa loudspeakers. At a little over 4' wide apiece, and with 8' between them and at least 2' between each and their sidewalls, that's a room width of no less than 20'. For depth it's at least 5' from the panels to the front wall, 8' from the panels to the listening position, and at least 5' from that position and the rear wall, for a minimum depth of 18'.