Actually, the main reason for directionality is pseudo-shielding. Anyone familiar with balanced, shielded cables and how they work understands why you can't truly shield a cable that only has electricity running in one direction. Well, what some cable manufacturers do is pseudo-balance it, and that requires tying the shield to the negative side on one end, and having it hang loose at the other.
directional cable?
Recently, a hi-fi store loaned me a certain speaker cable and indicated that the cable should be installed in one direction only. When I mentioned this instruction to a friend of mine who is an electronics engineer he laughed for an uncharacteristically long time and then wondered aloud why someone would apply directional bias to a signal that should move equally in either direction. If that were not the case he said you would have some form of diode. Reversing the cable made no audible difference but I have no idea what sonic traits I should listen for. Can anyone shine some light on this?