It seems only yesterday, but it's been 10 years since I began using the original Paradigm Reference Servo-15
subwoofer in my system. It was good then, and it still is, although a lot around it has changed. At first, I hooked it up via Paradigm's X-35 crossover, then via a Technics SH-AC500D surround processor, and finally to the subwoofer/LFE outputs of the various preamplifier-processors and A/V receivers I've used. Y'see, the Servo-15 is just a powered sub. It has an amp and a level control, but no crossover, no channel mixing, and no phase control. Just plug in the signal and it plays it. Along came in-room response correction from Audyssey, Anthem, Velodyne, etc., and the Servo-15 became an even better sub. For music, it entirely satisfies my needs.