Why do turntables sound different?

@inna 

When I refer to 'mass of the platter', I am referring to suspended mass. That is, loosely speaking, the mass supported by the thrust bearing, including spindle and mat (usually negligible). 

A physicist would normally speak of the moment of inertia, which is the physical analogue of mass in a rotating system, and which is most relevant to rotational stability. Moment of inertia is maximized when all the mass is on the outer ring, which is why some TT have mass distributed on the periphery.

But mass is easier to understand, and is highly correlated with moment of inertia in a solid object. Also, mass determines the weight which must be supported by the thrust bearing. The remaining forces acting on the spindle are radial, arising from asymmetrical rotation and belt tension, and are sometimes dealt with more casually.

@lewm 

"Which is why it would be most surprising of all if all turntables with pretensions to excellence were to sound the same. Which is why I cannot get my arms around this topic."

Most succinctly stated, Lew. Nevertheless, I think that the question has spawned some interesting discussion.

@has2be 

"I would suggest that quiet bearings would HAVE to be low in friction, period. The greater the friction the higher the noise."

Don't agree. I think that most would agree that the greater the friction the higher the energy to be dissipated. Energy can be dissipated by heat (microscopic motion) as well as by sound (macroscopic motion).

Just borrow the new Continuum Obsidian, you know, the one with the mag lev platter suspension, or Walker turntable, COPY it the best you can and don't worry about it. 

@terry9

I couldn’t disagree more. Your advocating in a turntable of all things that a higher level of friction in its bearing will not create more noise and vibration and the two are not related ? Sorry that’s ridiculous in my view. The whole idea of a bearing is to reduce friction between two surfaces. The better the bearing, the lower the friction and the quieter it spins, period. The best bearings for turntables have tighter tolerances in shaft and ball thus reduced friction AND quieter operation . Friction, that leads to vibration and noise and wear no matter how its dissipated between heat (leads to loss of lubrication , wear and premature failure),... and dissipated as sound, really, below a vibrating stylus that gets amplified about 800 times. Quiet and lower friction in this application go hand in hand. Do you actually suggest that higher friction in a turntable bearing won’t create and amplify vibrations, which is odd since reducing those energies from even being seems to be more a desire than fixing or ignoring its correlation. Most of the best turntables have bearings that certainly are both ruthlessly quiet AND as frictionless as possible. Slightest push and they spin effortlessly for far longer and with less need for the motor, also reducing noise. They reduce it at source , thus the platter and its design is even more effective.