Dave,
I have the same thing with my Velodyne sub. It's the servo that's making the humming noise. I called Velodyne when I first got mine, and they assured me that all servo-controlled subs make this noise. Mine is not as you describe "real loud", but if there's no audio being played, I can also hear mine from the listening position. It's too low to interfere with normal listening though.
Ken
I have the same thing with my Velodyne sub. It's the servo that's making the humming noise. I called Velodyne when I first got mine, and they assured me that all servo-controlled subs make this noise. Mine is not as you describe "real loud", but if there's no audio being played, I can also hear mine from the listening position. It's too low to interfere with normal listening though.
Ken