When I said power I meant line in this case. The sub is connected to the subwoofer line output of the receiver. Actually I tried using also the high input of the sub (I don;t wanted to do that having a line output for sub) and the results were the same. As long as you keep the volume low the sound it's fine, but when the sub starts to show some cone movement (and not really too much, and not violent at all) the distortion starts to appear.