Ha! Grumpy, you beat me to it as I had the same thought. What else could it be, since it is an AC signal?

There is much mystery surrounding interconnects and speaker cables, and it is not all caused by hind-end audio marketing foolishness. After all these years I really don't know why my field coil compression driver horn systems sound much better wired with simple 26 gauge copper magnet wire than with most any heavier/more complex geometry audio salon speaker cable, but they do. Lucky for me, my favorite cable costs about 50 cents per mile!