I received a Sony SA-WM500 powered subwoofer second hand. I was planning to use it for audio production purposes, short term before i flip it. I plugged my phone into it to test it with multiple different RCA to 3.5mm cords (i have no idea how powered subs work and if you'd be able to play from a phone in the first place). It was making no bass whatsoever. I plugged a speaker into it and it made the typical unamplified sound you'd expect from an unamped speaker.
Then, I plugged it into the non-powered subwoofer output of a 1994 Aiwa cx-n4000u amplifier. Suddenly i had great sub bass, along with the sound from multiple speakers already connected to the system.
The next time i tried playing something on it, it made no sound at all. Then the next, it took a long while to start but then suddenly started playing bass in the middle of the sound i was listening to. The next 2 times it did the same thing. Now days later it's not playing anything at all, even though it still has a power light the entire time. Every time that i fiddled with it for hours before, it eventually started working again. It was always something else that makes it work. Sometimes messing with volumes on both the amp and the sub (but never the same volumes work), sometimes replugging the RCA cable countless times, sometimes turning on and off the sub countless times, sometimes unplugging and replugging the power countless times, i still have no idea what's causing it to not work well. The auto power save feature switch doesn't seem to change much. No matter if it's on or off it always still auto power saves after a while it seems.
If i must, I can take the back plate off and check things back there. But, I was hoping not to as it's got probably 20 or more screws...