The SubXo uses a highly regarded for it's sonics, quad Burr-Brown FET cascode chip to perform the 4 filter functions needed for a competent active crossover for subwoofer use. The left and right signals from the preamp are filtered below (std) 150Hz at 12dB /octave (L-W std) and go to the main outputs at low impedance. The input signal is seperately summed and filtered aat 12dB/octave below 20Hz (Butterworth std) and above 150Hz (L-W std), to a low impedance buffered output. The unit includes it's own discrete 80dB regs and power supply requiring only a 12Vac or +/-18V DC supply. The unit has the facility to build in a bass eq function similar to the BassEx and independant gain setting of the sub out channel for level matching.