I called Nad; I was told that in Stereo Mode the T163 Preamp would not have a crossover function. I would be the same as having the speakers set to large. As test did show, both speakers were playing full range. I later found that I could set the HSU Subwoofer to the IN position and the sub would not play after the crossover. Dr. Hsu recommended a high pass filter for the mains.