Well I think centurygold was quite right. I have this system for about 6 months and indeed the subwoofer hums. there is nothing to do ... I hasten to sell it and find something better now for what will be not difficult.
Beware before you buy, ask to listen well to avoid unpleasant surprises. € 600 for putting in an audio system that works poorly ... is to throw money out the windows

I note one as indeed in the words so sellers is "design"