My M22's and HSU STF-2 are powered by a Harmon Kardon 3490 stereo receiver. The HK has two subwoofer outputs, but they run full range (no crossover in the receiver). The sub is connected to one of the HK's subwoofer outputs (low level)and I use the sub's crossover set at 60hz...with the M22's running full range. The sub blends seamlessly with the M22's.