Pure simple test tone 1K pink noise. available from many test cds ect. When properly spaced ect there will be air around and behind the "ball of sound" Be sure to use a movable chair to find the correct lock in point. This will bring imaging up to parr and will do nothing for optimum bass responce so you results will be used as a starting point.
One could use a mirror to find the refelction points on side walls ect to place sound absorbing material at that point to help with reflections.
One could use a mirror to find the refelction points on side walls ect to place sound absorbing material at that point to help with reflections.