Why does my subwoofer only connect to two tower speakers?

I take it that this is just a set of speakers and you have a receiver that you are trying to hook them up to. The simple answer is just hook the speakers that you can't get to work directly to the receiver and bypass the interface on the subwoofer. It's unlikely that that interface does anything anyway. However, given the quality of these speakers I would be very hesitant to hook them up to anything except a test amplifier with ample protection circuitry. These are one of the notorious "White Van" brands of speakers. a href="http://en.wikipedia.org/wiki/White_van_speaker_scam" rel="nofollow"http://en.wikipedia.org/wiki/White_van_s…/a Quality was not one of the factors that went into their design and they may well have impedance properties that could damage a receiver. I don't know what to tell you to do with them. If they were mine I'd either "vivisect" them being careful to recycle the parts properly or put them in the fire pit in my back yard where I burn yard waste. I'd be afraid to simply throw them out for fear that some innocent person would pick them up, try to use them and damage a perfectly good amplifier.