Does raising speaker cables off the floor really make a big difference?

Love to see a blind test of this.

It doesn't make a big difference in my system, but it does make a small positive difference, and besides that, you protect your expensive cables from dust bunnies.

Can't hear it.

Theoretically there should be a difference due to transmission line affect with the floor acting as a dielectric, and if the cables lie on the ground, there is a asymmetric affect - the ground act as a dielectric on the bottom half of the cable, but the top half of the cable only has the air as the dielectric.  By lifting the cable up, things are more symmetric as the cable will "see" the bottom and top the same.  But of course as with anything that has to do with audiophiles, your ears make the final judgement, theories not withstanding. 

Does raising speaker cables off the floor really make a big difference?

Not a whit, in my experience.  More illusory audio magic for highly suggestible audiophiles.