It's commonly known that to get smooth mid-bass and reduce boundary effects speakers should not be placed at equal distances from the front and sidewalls. But there is a formula that I just tried, developed by Roy Allison, that has greatly improved a dip I was getting at 150Hz. The formula is that the largest boundary distance (distance from the mid-woofer in the case of the X series), times the shortest distance should equal the middle distance squared. In my case, using X5's, the longest distance of 48" (the distance from the front wall) times the shortest distance of 27" (height of mid-woofer from floor) should equal the middle distance of 36" squared (distance to side wall). 48 x 27 = 1296. 36 X 36 = 1296. It's worth a try if you can manage it.
