High mass vs Low Mass Turntables - Sound difference?

I have had modest benefits using various sorbothane footers with turntables. I suspect they are more effective at blocking transmission of sound from whatever the turntable is sitting on than in reducing mechanical vibrations in the turntable, from the motor or platter. However I have found far better results applying small ( no dimension in excess of 1 inch) pieces of sorbothane to the body of the turntable. These need to be glued using the 3M self-stick which some sheets come with. I use a Lord industrial adhesive when I cannot get self-stick. This is however expensive and hard to find. I recommend thicker sorb, 1/4 to 1/2 inch and denser 70 duro.  Sorb's claim to fame is converting mechanical energy to heat, so it really seems to be getting rid of it. 

I would correct geoffkait on his claim that sorbothane needs to be constrained to work.  I have been using it unconstrained for years with  good results, on speakers, headphones cd players etc. However constraining, i.e. covering the surface which is not in contact with the equipment,  improves its use a lot. You do not need aluminum sheets.  I have worked with various clamping devices and found that very little force on the sorb worked best. In fact I simply use 4 layers of electrical tape and get great results and have ditched the metal clamps.