Well, upon urging from some on this thread, I just lifted my speaker cables off the floor (tile and carpet) using wooden blocks about an inch across and two inches high, four blocks per side.
I listened, put the blocks under the cables, listened again, took the blocks out, and listened again. I did not hear any difference.
I listened, put the blocks under the cables, listened again, took the blocks out, and listened again. I did not hear any difference.