Direct Drive turntables

Pryso, It depends on what you are trying to accomplish. If you want to get an accurate understanding of the sonic affect of a particular component then you want everything else to remain constant. In this case it's about gaining understanding and not necessarily optimizing for the best sound. With understanding of the contribution of various components in isolation then you are in a much better position to then optimize.

It is certainly possible to make meaningful judgments without everything else being equal but it is much more difficult and more error prone.

There is usually some synergy between components, but I believe that as the level of quality goes up this becomes less important. I think that a motor implementation that requires a particular tonearm or cartridge to sound optimal should be considered to be flawed. A quality, neutral implementation of any component should work very well with any other quality component. Of course in the real world this all too often is not the case. But it should be a goal of good design.

Changing drive alone would be a purely academic exercise, except for perhaps for those that might be willing to custom build their own table.

Practically, it is the overall design and integration (table, arm, cart, phono pre-amp) that matters for most. Any type of drive mechanism, if done well, will work just fine.

The experiment has been done by anyone who converted his Teres or VPI turntable from belt- to rim-drive using the motors now available from the respective manufacturers. In these instances, all other factors are held constant; only the drive system is changed. As far as I know, almost all end-users have preferred rim drive vs belt drive. One could be skeptical of those claims, because there is a lot of subconscious bias in favor of hearing an improvement, in my opinion, when one spends money for such "upgrades". (The very use of that term suggests a bias.) But I am inclined to believe that the benefits are real, based on my own completely uncontrolled experiments comparing a "good" belt drive table to various idler-and direct-drive ones. (I am a scientist by profession, so this stuff bothers me.)

I don't understand the aversion to measurements. If you don't like measurements, you don't have to do them or pay attention to them.

If measurements don't correlate with perceived improvements in sonics, then the measuring tool needs improvement. The poor correlation of THD and perceived sonics is a good example.

Audiophiles have differing tastes. The assumption that measurements cannot accomodate differing tastes is probably untrue. In fact, if an audiophile was able to correlate measurements with his or her sonic preferences, it would likely improve the his or her ability to predict whether a particular purchase will be satisfying. Just a hypothesis.

Regarding belt drive slippage. Let's assume for the moment that a) the stylus places meaningful drag on the platter, and b) such drag varies in intensity with the shape of the grooves of a record, and c) the variation in intensity affects rotational speed to a degree that it creates an objectional variation in pitch. It would seem, to me, that compensating for the problem by "belt slippage" is akin to a servo motor that always reacts after the fact. So, to compensate for the inaccuracy of the servo motor (belt slippage) you use a very heavy platter so that the affect of the stylus drag upon the rotational speed of the platter drops below an objectionable degree of variation in pitch. I understand the hypothesis that the mass of the platter minimizes pitch variation.

I don't understand the hypothesis that belt slippage does something to minimize pitch variation. a) Why? b) How would you control belt slippage so that it acts predictably and with repeatable results?

In regards to testing drive systems, here are a couple of ideas. Test 1. Place very tiny hash marks next to a groove of a record. Play it and film it with a high speed camera or strobe (using a macro lense or microscope). Measure the speed of the stylus against the hash marks. Switch turntables and repeat. Compare the speed of the stylus over the same section of grooves. Test 2. Take a teres turntable. Play a short, dynamic, section of a record. Record the output from the loudspeakers using a microphone and input it into a computer. Do it for the belt drive version and the rim drive and use the same record grooves for each. Load the sampling into a computer software program that charts frequency and transients over time. Compare the durations and frequencies of the samplings by graphing one sample over the other where the x axis is time and the y axis is frequency.

Jeff

Lew, you offer a great example of comparison and I should have remembered it. A friend of mine owned a VPI Scout and became curious about the current rim drives. Although it cost about the same as his table and arm, he ordered the VERUS rim drive/controller system. There has been full agreement by everyone who has heard it that this rim drive plays more realistic and satisfying music. Interestingly he took this system to his VPI dealer where they compared the original belt drive to the VPI rim drive to the VERUS. Each of the three produced a different sound.

So I guess there are limited opportunities to compare different drive systems. But I still feel in most cases one could not make a fair comparison as to which system is "best" or "most musically satisfying" when the set up for each system is not optimized for the best results with each individual drive system.