Old thread but -- elevating my cables off the ground with pillows dramatically reduces induced RFI (local radio station) that I can otherwise hear through the speakers at a close listening distance. Elevate them, and I need to hold my ear up to the panel to hear a (now very faint) radio station. So there are electrical differences that affect cables when they lie on the ground, at least for some systems. In my case, the "floor" is concrete. I imagine the boundary may have a positive effect on the EM field that expands around the cable as well.
