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

Only if someone else holds them up.

I can't believe the ghost of Enid Lumley is still with us.  That woman has done more to advance the snake oil industry than anyone else.  I remember her going on about the audio qualities of different kinds of shellac on floors.  I still have many of the Absolute Sound issues where she writes in.

I tried this years ago when I first bought expensive cables at the advice of the salesman. I never noticed a difference then, tried it a couple of times since still never heard a difference. This always seemed  to me as one of the more questionable notions in the tweak universe. 

I hate to be the one to bring this up but there appears to be an awful lot outliers here. That’s a shame! Keep on trucking, mama, truck those blues away! 🚶🏻‍♂️