Direct drive vs belt vs rim vs idler arm

Gentlepeople
The problem with posts like this, where a difference in opinion is being aired, is that there is a tendnacy for us to talk past eachother and place significance on things that are written outside of what the author meant. This is perfectly natural.
That said I will try to clarify what I meant with my six points.
1) and 2) The Final has higher intrinsic resistance to stylus drag due to its platter which has a higher moment of inertia than the other two TTs, ONLY if you turn off their servos.
With the servo in play The SP10MK3 will show NO measurable speed change with retardation torque levels up to 10KG/cm. In their literature they use the analogy of 1000 cartridges tracking simultaenously. So we can infer from this that 1001 cartridges tracking will cause a speed change. I note that the Final slows down with 1 cartridge tracking. Lets make this clear, speed change due to stylus drag on the SP10MK3, even with 1000 cartridges in play, is so small that it is undetectable. You can take it then that I did do not acknowledge that the initial drop of in speed would be higher with the DDs. While a speed change must be there, with the SP10, it is not measurable. This is where correct matching of motor torque capability, servo characteristics and platter moment of inertia are critical.
I do not have data on the LO7D, but I expect that it would also perform well on this front.
For me the problem with speed changes due to stylus drag is that they are a function of the music being played, unlike wow and flutter which are independant of the music. Much like tape hiss, we can listen past w&f to engage with the music. This is not possible with stylus drag speed problems, as it is inside the music itself. That said it is obvious that lower w&f would be better.
Record concentricity problems are a pain especialy when one has just put down good money for a new record. But this is not a platter speed accuracy issue, so in that sense it is spurious to any discussion on absolute platter speed accuracy, even if its effect dwarfs any platter speed errors.
3)Cogging. I don't want to put words in your mouth, but I don't think that what you are hearing is actually motor cogging as in the physical effect of the motors construction. The very low frequency at which actual cogging occurs is, I suspect, not what bothers you. I do agree that there is a problem with many DD's, but it is not physical motor cogging and it can be fixed. (Maybe the Goldmund should be outside this comment.)
4) 5) Stasis torque levels. The platter will speed up if the torque output from the motor exceeds that requied to overcome bearing friction, stylus drag and windage. Not enough torque and the platter will slow down. Drive systems revert to stasis (low maintenance ) torque levels once design speed is reached. This is taught in engineering classes. Putting this another way. Motor torque output is a function of the load.
6) You are totally correct when stating that the DDs need a lot of work to bring them up to their potetnial. This, however, does not detract from the fundamental performance of the drive method.
Lewm said "If you prefer your thread drive to any and all direct-drives you have ever heard, that is all well and good. I am sure it is superb. But I don't think you can prove from first principles that it is inherently superior to all direct drive."
Totally correct. The opposite is also true, so let's call it a day and both enjoy this thrilling hobby of ours.

Dear Dover, I have no issue with anything you say, where it's a matter of opinion. And I believe you are totally honest when you relate to us that there is something about the "sound" of the direct-drive turntables with which you are familiar that you don't like, or you don't like as much as you like your Final. Quite apart from what Richard says, my problem with your statements is that you are relating whatever it is you don't like about DD to a known issue with all motors (cogging) or to servo effect. As audiophiles we all have the tendency to impute cause-effect relationships like this, when in fact few of us ever do the necessary experiments to prove the relationship. You may dislike DD; that's fine. But you don't know that what you don't like is directly related to cogging or servo. (In fact, which is it, cogging or servo action? You change the tune on that with regularity.)

In my system, I have a highly tweaked Lenco, a Technics SP10 Mk3, and an L07D, all set up side by side by side. They are each very different from one another in the method by which speed is "controlled". (As I have mentioned previously, the only meaningful attack on cogging is the coreless motor; L07D has that feature. But the Mk3 is just as good if not a touch superior to the L07D, with its monster "cogging" motor.) They are all superb turntables; they are more remarkable for their similarity in "sound" than they are for their differences in sound.

I hope that the DD turntables upon which you have made your judgement were properly serviced and adjusted. Leaky capacitors and the consequences of same (blown solid state devices in the speed control electronics) can take a toll on the performance of DD turntables that is not readily apparent, i.e., the table may still "work" but may not be working to its max.

Lewm - in my posts I have tried to relate what I hear with the design etc. Some folk misread stuff. I am not anti direct drive or any drive. What I have heard in very good systems is that there are very few DD's that dont sound awful, by which I mean grainy, grey, music dissembled, fragmented, a lack of dynamics and transparency. The only ones I've heard that dont sound awful are the SP10mk3 and L07D. The Goldmund I heard had a rebuilt and upgraded power supply, many other upgrades and was in very good state of tune. The standard L07D demolished it - demolished it. Demolished it in terms of speed and timing. The Kenwood sounded more lucid, crisper and cleaner. I use this example to illustrate that in my view if you are running direct drive it needs to be at the level of the SP10mk3/L07D at least or you may be better off with an idler or belt drive. Ironically the Goldmund would probably pass the Timeline test, so the Timeline test is very valuable to give you assurance that the basic speed is accurate and maintained, but then we get into the dirty unknown. What happens in between at the micro level.
I have made a statement supported by physics that the high inertia of the Final will result in deceleration due to stylus lag variation of 1/4 in magnitude of that of the Technics SP10mk3 and Kenwood L07D. Furthermore results that quantified the stylus drag with and without the stylus playing are at a level less than the wow and flutter levels of the Technics SP10mk3 and Kenwood L07D.
A counter argument has been proposed that properly designed servo speed correction is a fundamental requirement for any TT. No numbers or empirical evidence have been put forward.
This is the nub - both the Final and the SP10mk3 are 2 of the best TT's made, they are at or near the top of the tree - so the question is what if you cant afford or obtain the top of the tree? What compromises should you make if you are going to make any ? Most think that what they have is the best. My nature is to try and understand why things sound the way they do. I have been able to improve my system by doing this - understanding what I have, its design construct and selecting products that achieve the goals which for me are important, speed, timing, coherency, harmonic structure. I personally dont have perfect pitch, but I'm extemely sensitive to timing - if the timing is off, I cant stand the music, fall asleep, lose interest.
The posts here that have references to gear I might have heard, hard facts are valuable and enlightening. Recent examples are Halcro's speed testing and Mosins' debate on belt creep which led me to study up previous posts and discussions on vintage idler motors, which was informative. Folk shouldn't get offended by posts - just get pissed off enough to go away and do some research. We all learn from this process.

Richardkrebs :

Let's assume we are tracking at 2.0g.
Now let's break down the stylus drag components into 2 parts - one being stylus drag due to the tracking force ( A ) and the other being the variation in stylus drag due to the variations in the music ( B ).

I measured A, not B.

A - Stylus Drag Due to Tracking Force ( assume constant ).

When you drop the stylus into the groove the high inertia TT drops 0.008%.
( By the way - this was a very conservative estimate to avoid debate, it's actually less )
Now I believe the Technics will drop by 4 times this if the servos are not on due to the lower inertia.
The Technics maintains speed because the servo kicks in.
This is no different to me adjusting the speed via the controller to account for the constant drag...except for the following -
When I bring the speed up to adjust for the 2.0g tracking force I bring it up manually until it the speed is stable.
The Technics servo will react by increasing the speed. The catch here is that the servos only react to errors or changes in load and they dont know the magnitude of whats coming, so they ramp up the response until such time as they detect the speed is too fast - they overshoot. Then they have to correct for the overshoot. This becomes a constant cycle of overshoot and undershoot. You might not be able to measure it, but it is there.

B - Stylus Drag due to Variations in Music

I cannot measure any stylus drag with the high inertia TT. I checked for variations on both inner and outer grooves.
I assume if it exists it is too small to measure.
Same argument exists as in A above, if there is any variation then your DD servo will kick in according to some preprogrammed parameters, and once the servo kicks in, again you end up with micro overshoot and undershoot - too slow, servo, too fast, servo, too slow etc

Now we can argue until the cows come home a to which is better or worse, and which cow comes home first will vary depending on the design and quality of the individual design.

Wow and flutter versus Stylus Drag
I would give equal weight to these. If I am listening to a piano concerto, I want to hear the attack, intensity and decay of each note as well as the ebb and flow of the performance.
I would also suggest that to reproduce the attack, intensity and decay of the note, then the record/platter interface and platter/bearing/plinth design and how it deals with excess energy and maintaing a rigid loop will have a major bearing as well as stylus drag. Certainly the designers of the Final believe there is significantly more energy generated than that required to move the stylus which needs to be dealt with effectively, whilst maintaining a rigid loop between cartridge and record to measure the groove accurately. Removal of this excess energy in my experience is analogous to lowering the noise floor - increased resolution, less smearing of notes.

Re the cogging : I cannot be sure that the instability I heard is cogging. I have described what I heard a the response to Lewm which was posted prior to your last response. It may be the servos, lack of inertia or other issues, but I would add to your comments that cogging can be induced by poor power supply design if the current waveform driving the motor is not maintained accurately as well as the motor itself. I have seen a number of TT's where the power supply regulation is poorly designed and literally turns on and off whilst playing.

Cheers.

Dover I personally would like to know what your main system consists of?

There is a reason for this

Lawrence
Fidelity Forward