I have already tried a Mirage FRX80 8 inch front firing sub with a Velodyne CT80 8 inch front firing sub. I am splitting the mono signal coming out of my receiver and sending one line to each. I have also put y rca's to the single inputs to get a Right ad Left input on each sub in the hopes that it will improve the signal. I have them placed on the inside of the two front Boston VR950 mains.