Is Direct Drive Really Better?

Specs...It is obvious that the sonic character of a loudspeaker cannot be defined by specs, although some things like frequency response can be usefully measured. However performance requirements of a TT (not the arm/cartridge) are so simple that I think that specs can tell the whole story.

1..A TT must rotate the LP at exactly correct speed, and without speed variation for reasonable stylus drag force variation.
2..A TT must not generate a magnetic field at the cartridge.
3..A TT must not generate vibration, for example rumble.
4..A TT must attenuate vibration of the base it is mounted on.

All these can be accurately measured. The only issue is to determine what acceptable values might be.

And remember that the real reason for specs is for the manufacturer to verify that each unit he builds has been properly manufactured and assembled so that it performs as well as the design permits. Use of specs to assess the quality of the design is something extra that people do with specs. It is more valid for TT than for most other audio equipment.

As a proponent of the "niche market" rim drive group, I would suggest that Eldartford omits probably the most important character of the TT-resonance frequencies. I grant that he does mention vibrations. My real question, as always, is how do specs. capture this. Again as always, all I want is to hear the TT. I did hear the Shindo/Garrard 301, and I bought it.

I should say that regardless of how good it sounded, putting it on the Halcyonic base greatly improved it. Again resonances. Would it not be great to have freedom from resonances.

Dear friends: There is other point that " speaks " in favor of the DD system:

from what I know the cutting lathe machines ( that " make " the LP ), like Neumann, Fairchild, Scully, etc, etc, has DD design not BD/IW. Wonder why?, yes you have the answer.

Regards and enjoy the music.
Raul.

Thanks Teres for elaborating. Guess it's a good thing you feel your product development results have affirmed the theoretical reasoning which preceded them :-)

On somewhat of a sidetrack note, let me toss out a bit of theoretical reasoning of my own. I think almost everbody in the business could have it backwards in placing substantial platter mass out near the rim. I know why it's done, but suspect that in a different sense it might be a disease worse than the cure. IMO it could be much better from a resonance standpoint to concentrate whatever mass is required for inertial effect as close to the bearing axis as possible and make the outer regions as light as practical. I understand this would entail use of greater mass overall if one wanted to achieve an equivalent inertial effect. But locating mass very far away from its point of mechanical constraint (the main bearing) is inviting trouble in my estimation. Given that a platter must have a flat top, I think maybe a parabolically-curved underside, yielding a constantly varying thickness, might work well...something like this half-profile:
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(Sorry, the system doesn't permit the full illustration without justifying it, so imagine it mirrored with the bearing axis at the left margin.) Of course the bearing-point itself would be up inside the shape, slightly above its center of mass. Looking at this, I wonder if possibly the York TT that Fremer has sometimes pictured in his column might not have a similar platter profile, but I don't really know and can't think another myself. But if it does, that makes more sense to me than the common approaches. End of off-topic musings...

Hi Raul, from a quick Google: "scully lathes where made by larry scully. most of them where made in the 40ies and there are still lot of them working. nicely made. optical much more exciting than a neumann the quality was never comparable. althought most of todays "audiophile" records where cut on these lathes.
nice feature of the 1940ies scullys is the inside out leadscrew. you have 2 leadscews. one for cut normal and one for inside out cuts...
the first lathes where all fixed pitch with a gear box. lather models ha a very complicated "vary-groove" mechanism where tube electronics controlled a strange mechanism to varie the pitch.
the biggest disadvantage on scully lathes was the belt driven turntable. with a asynchrounous motor, 2 belts and a heavy clutch the turntable was never that strong and stable.."

Emphasis on "although most of todays "audiophile" records were cut on these lathes." Evidently the cutting lathe technology is no way to tell which is the superior system.

Direct drive is a recent development, early cutting lathes (used to produce records we still listen to and value) used motor-driven gears as well, and its use today in making master discs does not enlighten as to which is the superior system overall, given the presence of assumptions, and the need for the ability to minutely variate the speed of the cutting motor/platter: "Between 1953 and 1955, Neumann developed a method of varying the groove pitch depending on the recorded amplitude. To this end, an additional playback head was mounted on the tape deck. This additional playback head determined the groove amplitude to be recorded approximately one half-rotation of the turntable in advance and fed this value to the cutting lathe as a control signal via a corresponding drive amplifier. Of course, this also required a separately variable pitch drive. For the first time, this made it possible to extend the playing time of an LP phonograph record to approx. thirty minutes."

In playback speed stability in practice, not the ability to vary the speed to accomodate the creation of groove modulations in cutting grooves, is the key. The problem of distortion-inducing vibration/noise is a given and it is the responsibility of the purchaser to correctly set-up any turntable, belt-drive, DD or Idler, suspended or unsuspended, there is no magic bullet. Apparently Van den Hul has his turntable set-up on a concrete pillar sunk deep into the ground! The best way to determine speed stability given the problem of which measurements are meaningful, is the human ear. Back to comparisons in front of witnesses, i.e. demonstrations! Theories must be tested to be verified - or discarded - and the human ear is the final arbiter.

Once again for the Gipper!:
"If it measures good and sounds bad, it is bad;
if it measures bad and sounds good, you have measured the wrong thing."

- Daniel R. von Recklinghausen,
former Chief Research Engineer, H.H. Scott