Why do turntables sound different?

I venture to suggest that quiet bearings are more important than low friction bearings. The two may not be the same. Although air bearings do seem to be best in both respects.

Also important is the resonance of the platter, especially in designs which do not use air bearings.

Just two of the considerations which affected my DIY.

@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).

@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.

@has2be 

"Do you actually suggest that higher friction in a turntable bearing won’t create and amplify vibrations ..."

Got it in one. Almost. I repeat, "The two may not be the same."  I also repeat, "Energy can be dissipated by heat (microscopic motion) as well as by sound (macroscopic motion)."

You say, "... which is odd since reducing those energies from even being seems to be more a desire than fixing or ignoring its correlation." Do you mean, "it is desirable to prevent those energies from arising, rather than fixing them"? Is that what you were trying to say?

If so, then I agree with that. I use air bearings and mag lev myself. But that is irrelevant to the point of how all bearings must function.

You have made categorical statements about how all bearings work: that macroscopic noise is a monotonic function of friction. I don't think so, and it's going to take more than an a priori argument to convince me - this is a matter of physics, not metaphysics.

Has, I remain wholly unconvinced.