Oh, it's probably not a good guess. I found the review I was thinking of, and it wasn't really humming or buzzing, but something much more severe.
http://www.6moons.com/audioreviews/axiom/axiom_2.html"Making a long story short, I came to realize -- and had it verified by Axiom -- that if the subwoofer is placed too close to the speakers without a signal running through the system, the speakers and the subwoofer become... um, bored. They start talking to each other. I'm not sure who starts the conversation but the speaker talks to the sub, which responds in kind. As with any feedback loop, voices raise and eventually, it becomes an extremely loud conversation at an extremely low frequency. This electronic feedback conversation was notable in that it occurred at so low a frequency as to be inaudible. But it was reproduced with enough raw power to rattle the hell out of my room. It was at this point that I knew this thing was going to be fun! But I was going to have to send the speakers and sub to neutral corners."
Still, maybe it could have something to do with it?
