The late Pierre Sprey of Mapleshade said it was the poly fibers in most carpet holding a static charge that was the reason to use cable lifters. Thus they needed to be some distance off the floor, I seem to remember 18" as the figure, please don't quote my failing memory. He also maintained the lifts can't be plastic or metal, wood is suitable. I've used cable lifters cause they're cheap and make vacuuming easier, but I've never really heard a repeatable difference. I wonder if going with something over a foot and a half of rise would make a dramatic difference in sound quality.