I've been reading threads about 'hum' today and getting more and more discouraged. My Klipsch KTSW powered subwoofer was part of a THX 5.1 system that I put together 20 years ago. Frankly I haven't used it as much as I intended when I put the system together, and I've never cranked the volume very high. I have a mcintosh c39 preamp and mcintosh power amp (forgetting the model number, but those amps never clip signals, so I'm pretty confident I didn't destroy the speaker myself).
The subwoofer hums loud enough to be useless. It 'works' otherwise. Indicator light is green; hum present even when speaker cables disconnected, as soon as power turned on. Volume control and frequency switch have NO impact on volume of humming noise.
Any thoughts with this recognizably-limited information? This thing is so heavy I'm not sure how I'll get it to my car, let alone find someone in small-town Wisconsin to try to fix it...