Is Direct Drive Really Better?

4yanx,
Your observations registered on this end as both wonderfully incisive and appropriately cynical.
I think that the Chinese idler wheel turntable might appear if Schifter or Nudell or someone of that ilk finds the demographics are there to support such an endeavor. Perhaps we'll be seeing the Johnnantais Signature Model with the new Lega arm.

"I would surmise that the boulder would be slowed somewhat by your body since it was coasting whereas the car which is actively powered could be completely unaffected by your presence in its path."

I think you'll find both are slowed. Cars are slowed by headwinds, even though they are powered. A car is slowed when it hits a tree, even when it's powered. A large rock rolling down a hill can smash to splinters a tree that would stop a car dead in its tracks. Even if the incline is very slight, such that the gravitational force acting to roll the rock is very small the rock carries a lot of energy in its inertia.

All I'm saying is that I cannot see any way in which high torque/low inertia is inherently superior to high inertia/low torque, for purposes of speed stsbility.

Sean, you forget that the high inertia set-up, as you put it, also has high torque. Torque being force X distance from center, the torque being exerted at the distance where the stylus is from the center. Having inerta as an added 'store' of force, is a good thing. The fact that the motor is low torque is irrelevant since the torque is multiplied by the 'pulley' ratios.
Put another way, depending on the polar moment of inertia of either system, the one with the largest moment of inertia will be less disturbed by quick changes of drag. The 'high torque' direct motor only delivers the amount of torque necessary to turn the platter at the constant speed under X drag conditions. Unless it can react immediately to the sudden increase in drag, it will be disturbed in speed. The high inertia platter however has torque stored, so-to-speak, as inertia and therefore is less affected by the sudden increase in drag.
I guess that that is your arguement?

Bob P.

Can't speak for Sean, but it seems to me that is the argument. For example, the Nottingham has such a low torque motor (but high inertia platter) that you have to give it push to get the platter going. That's by design.

Bob ... actually you and I are in agreement. The torque is either in the high mass platter, or in the motor, or it is in both. Where it is doesn't matter, what matters is that there is plenty of it.

I'd even go further and say that, I would expect the theory to favor a belt driven table of very high mass, and with a very low torque motor, since a revolving high mass not only has plenty of torque, but because of the low torque motor it should also have a very high degree of speed stability, and noise rejection. The difficulty in the high torque motor approach is guaranteeing that the high torque motor is low noise, and has an extremely stable rotational speed.

But I'd still like to hear a Lenco, Garrard and SP10, and I'd be happy to buy whatever sounded best to me, regardless of my theoretical preconceptions.

My experience has been that solo piano is the torture test for turntable speed stability, so a dose of Beethoven piano sonatas should be all that's required to find the best turntable.