Need help troubleshooting audio system

Hi, I have a strange sound coming out of the woofers of one of my speakers. It sounds a little bit like a computer loading, a low frequency hum that can be heard from 10 feet away from the speakers when music isn't playing, and it seems to come and go at random.

My sound system is a little complicated and my technical knowledge is limited so I was hoping I could get suggestions on what to check first so I can minimize the chance of messing anything up. My equipments consists of the following: Squeezebox Duet, Bel Canto DAC3, a pair of active crossovers associated with my speakers and subs, 2 Wyred 4 sound 5 channel amplifiers (one for each speaker and subwoofer), and Linkwitz Orion+ speakers and Thor subwoofers.

The noise occurs even when my DAC and Squeezebox are off so I at least know it's further downstream than that, but the problem can still be in the crossovers, the amplifier channel corresponding to that particular woofer, RCA cables connecting crossover to amp, speaker cables connecting amp to woofer, or a problem with the woofer itself.

Anyone have any idea what might be causing the problem before I mess with everything so I can minimize the potential for damaging my equipment?
There is not easy way to locate the problem you are having.
I would disconnect one item at a time and reconnect till you find what is causing the problem. You also might want to try moving some of your wires around, you could be having an issue with EMF. Try to make sure than your power cords cross your interconnects at 90 degrees or are apart by 6" or more. I myself run my power cables down one side and the interconnects down the other side of my rack if possible. I also like my speaker wires flat with no coils.