Direct Drive turntables

"Direct drive was a fad."

Ridiculous.

I have one of Oregon's Lencos and it embarrassed my former expensive belt drive table.

It never ceases to amaze me how many audio nuts propound theories without data. And when folks ask for data usually the answer is it's too complex to measure or we measure the wrong thing. Or, it's so obvious that no testing is necessary.

Are you really saying that none of you physics guys can figure a way to measure a) slippage due to stylus drag and its effect on dd versus bd, b) the similar effects of a vacuum and spindle clamp, and c) the constancy and behavior of the hypothesis that belt drive slippage averages a high mass platter even in the instance of variable amounts of stylus drag? Last, nobody has attempted to measure human sensitivity to pitch (speed) variation relative to the duration of measurement? If I were a manufacturer, I could turn a kitchen daisy wheel at exactly 33.3 if you gave me enough time to manipulate it.

FWIW, I vote that agon creates a science first forum where opinions must be backed by data (or references thereto).

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

Teres, thank you for a very articulate explanation.

I agree that our ears and our perception are more important than a number on paper. I do believe that with study, we will learn to improve our correlation between measurements and sonic satisfaction. If a measurement does not correlate with perceived sonic satisfaction, then the measuring system needs improvement and such theory does not bar individualism.

In other words, if a measurement not help then throw it out.

I did not propose that the goal of measurements is accuracy. (Although in the determination of platter stability pertinent to belt drive versus direct drive, accuracy of constant rotational speed probably is the goal). For somebody who likes colorations, measurable inaccuracy may be the goal.

For example, Raul cites an audiophile who likes colorations. Raul appears to dislike artificial colorations. It is not my duty or right to tell somebody what they should like. It is conceivable that measurements, graphs and other repeatable and predictive forms of communication could help each of these two audiophiles get what they want.

So, I believe that if a consumer wants pitch stability that is suitable to his personal demands, reliable measurements that describe the differences between the platter rotation of belt drive versus direct drive would help the consumer (and not help turntable manufacturers who don't want to learn and improve).