A Few Turntable Measurements using the RPM Android App

What Lew said. Low torque motors transmit minimal vibration and noise to the platter (and all parts of the table) Some belt drives use tooth floss for example to further reduce transmission of motor artifacts while relying on inertial mass to keep the platter spinning accurately. 

I cannot think of a reason why AS decided to do this. I can’t see an engineering reason.

This is one of the eternal arguments among vinylphiles. In belt drive world, we have the light platter/high torque motor crowd vs the heavy platter/low torque motor acolytes. Then we have the idler/DD aficionados who jeer (privately) at both. Modern methods of speed control have leveled the playing field somewhat. My dirty little secret is that I finally couldn’t stand the ritual of having to push start my otherwise perfectly good Nottingham TT and so was driven to experiment with idler and direct drive. (On one occasion I nearly knocked the Nottingham off its wall shelf with my overzealous push start.)

@lewm I have not been able to find specs on the Nottingham or the Walker tables. It is quite difficult to make comparisons on table performance without basic speed and vibration specs. I will never buy a table again without seeing these specs.

One's ears are far less sensitive than the equipment used to measure table speed and vibration performance.

As is often the case, measurement is the issue. RPM is a continuous quantity only in the abstract. In all practical applications, it is an average. Maybe over a fraction of a millisecond, but that still is a far cry from continuous.

So the major issue, variations on the 10 - 20 KHz level, may be averaged out and not be addressed at all. Unless the specs indicate the time span over which the average is taken, the results don't mean much. As one of the greats from the glory days of audio once told me, "The best audio analyzer available is hardwired to your brain." (Jonas Miller)

I like the Nottingham sound too, which is why I built my air bearing with a 45Kg platter and a 1.8 watt motor.

@terry9 Like with many quantities, the speed aspects of turntable rpm can be described as a mean surrounded by skirts on either side. I say this with trepidation, because the turntable noise is not a stochastic (random) phenomenon. It can have resonances, for example. However, narrowing the width of the frequency spread and diminishing the signal from resonant sources is a worthy goal.

Some say that a turntable that has poor rpm control cannot bring out all the nuance that a high end cartridge can pick up from an LP. This reason alone is why some people are interested in the stability of the RPM. The human ear is not a good instrument to evaluate rpm. One may prefer one or an other method of rpm control because the sound of one is more pleasing than the other. Comparisons based solely on listening is obviously important. This type of comparison is not quantifiable by nature. Specs are there to provide a guide to potential users.

Engineers develop a product based on numerical specifications that the company's sales and marketing generates. Engineers use test instrumentation to measure and compare design approaches. Without a formal methodology and explicit specifications, engineers do not know what nor how to build a product. And importantly, when to stop engineering and consider the problem solved.

Measuring performance parameters of instruments is crucial to product development.

Any company that does not report these values via a spec sheet is denying the customer one way to evaluate and compare different instruments. Some customers need to see these specs because they provide a baseline for the performance of the instrument.

Not publishing a spec prevents that from happening. Often known code words or phrases are used to appeal to the emotions of particular enthusiasts. These are not specs. Perhaps some don't care. I do.