Turntable speed accuracy

You're right of course Decibell.
The 'correction' to any stylus drag speed reduction is so instantaneous...that we cannot see it on the Timeline.
What I really meant to say was........once a speed shift has occurred....without any instaneous correction.....no turntable motor will 'speed up' to 'remove' that abberation over the course of a few revolutions and thus restore the Timeline laser to its mark on the wall?
Yet with a strobe.......all will seem to be runnIng perfectly immediately after a speed shift (or even during if you blink).

Halcro,
I think you're on the wrong track ...
Simple physics dictates that speed must "swing" above and below 33 1/3 rpm in order to average out at 33 1/3. A speed change to below 33 1/3 HAS to occur first, before it can be detected and then corrected by applying more torque. If a drive mechanism does not "make up for lost time", the timeline laser would slowly, but constantly drift. The fact that these speed changes are very very small make it difficult to understand, but they have to be there in order to be corrected. Without any servo circuit measuring and correcting speed changes, the speed-torque curve of the electric motor would have to be a vertical line ... and there simply is no such thing.
You are right, it is very problematic to ceorrect speed in a way that our hearing tolerates it. The very high torque drive system of a Technics SP-10 MK3 or a JVC TT-101 sound much different from a low torque direct drive, but they both are able to maintain correct AVERAGE speed of 33 1/3 and the timeline laser will not show a differnce.

Dear Halcro, 'but the way many are discussing ...strobes (versus) Timeline...symply leaves me open-mouthed.'
You are suggesting the lack of intellect while it is about simple psychology. A phenomenon which can be observed in nearly any thread.

Regards,

Thanks Rugyboogie,
The video was very amateurish but I think....made its point.
Hollywood has not been ringing though which is puzzling?
You are one of the 'brave' ones amongst us....having purchased the Timeline only to find disillusionment with the macro accuracy of most belt-drive turntables.
However I believe the truth can help you.....and you happily have plans to correct the situation with the Verdier.
I certainly wish you luck.

Pryso,
Yes you are misunderstanding the principle of the Timeline as also Lew continues to do despite me trying to explain it on 2 or 3 occasions?
A turntable......any turntable......will not 'make up' for lost speed.
If a turntable did this......it would simply be unlistenable as it would never be revolving at the correct speed. This is a common misconception about servo-controlled DD motors.
A turntable must revolve at a 'constant' speed. If that 'constant speed is not exactly 33.3rpm......it is only a matter of 'pitch'.
When something occurs to 'alter' that speed momentarily.......it will almost always slow it down (stylus drag). When the motor detects that 'slow-down'....it will compensate to regain its 'correct' speed. It will NOT 'correct' that slow speed to another 'incorrect' FAST speed?
Thus the original 'altered' speed (due to stylus drag)....is a historical event that the turntable motor does not 'remember'.
The Timeline however.......will keep the record of that altered speed as long as it keeps revolving and thus the laser line will NEVER 'recover' to once again hit the mark on the wall.
This is the difference between a strobe and the Timeline. With a strobe....any speed change is so quick that a blink of your eye will simply miss it and the strobe has regained its 'correct' speed before you ever see it. With a strobe....there is no 'record' of the speed change.
With the Timeline.......a 'running' record is automatically kept and cannot be erased.
I hope this is somehow clearer........but the way many here are discussing the accuracy of different strobes to the way the Timeline is designed to function......simply leaves me open-mouthed :^O

My mistake, Thuchan. So therefore the allnic and the timekeeper would be about the same. I thought I had read elsewhere that the allnic light needs to be plugged in to AC.

Runout is the measurement of the eccentric motion in a rotating body. What I have been talking about in terms of a record is that the center axis of the record grooves are not matched precisely to the center axis of the platter. (Shaft runout would normally be measured in V-blocks in a lab and would consist of a combination of roundness as well as straightness of the shaft.) Additionally, the platter can have some runout- hopefully that is nearly unmeasurable considering the cost of some of these platters. The best way to measure the runout of a record would be to measure the swinging motion of the tonearm when it is playing a round groove at the inner diameter of the record. It would be difficult to measure while playing in the music groove since the tone arm is continuously moving inward towards the center of the record. The OD of the record is likely not that round and not necessarily tied dimensionally back to the music groove. I would say that if you can discern a swaying motion in the tonearm with your eyes as it is running in the music groove, then the runout is probably high. This was the case with my test record. But even then, I could hear the Wow only when playing pure test tones.

Rugyboogie, I meant with one belt drive TT, sorry!

best @ fun only

Dear Lewm,
the Allnic SpeedNic is battery powered and not so bad as you think...
also it allows adjusting during play.
I am not selling this product :-)

Rugyboogie,
you are in very comfortable situation with one running turntable ;-)

best @ fun only

Tonywinsc, you have used the term "runout" several times. I believe this is intended to relate to the accurate centering of the record. But in all my years in this hobby I've only heard the term runout applied to the area at the end of the recorded material where the stylus rides a continuous circle. Am I the only one not understanding this term?

Now back to the basic subject of this post. It seems to me the motor/bearing/platter have four tasks:
- providing a stable platform for the record,
- not introducing any noise which may be picked up by the stylus,
- rotating the record accurately at the desired speed (this might be considered the overall average speed), and
- maintaining that speed through the mili-seconds when interference might occur from imperfect motor rotation, power line fluctuation, stylus drag, etc.

If I am correct, it is the last of these tasks which may be the most difficult to achieve. I've never seen a Timeline, only a demo video. But I have two comments. First I agree with Lew that the distance to the sensor mark would be important. But secondly if the mili-second interference does not occur at the point when the sensor mark is reached the error may not be noticed. In other words the speed might have recovered by the time the sensor hits the mark. Does this make sense or am I misunderstanding something basic here?

Accuracy or sensitivity of speed monitor device should be proportional to (1) distance of sensor from center of rotate (longer radius is better) and (2) stability of the strobe at 60 hz per second. Ergo in theory the kab strobe (battery powered and not subject to AC line frequency variations) should be superior to timeline (batt power but v short radius) and to allnic (worst, with AC line power AND short radius). Admittedly, the kab is least convenient.

Purchased a Timeline last year after my Clearaudio strobe stopped working. The cost to replace the Clearaudio strobe was close to the price of a new Timeline.
Having used the CA since I bought my Verdier back in 2006, I found it easy to use and was able to set and forget about the speed. Enjoyed the music immensely on my table.
Since using the Timeline my perspective has changed.
At first I could not believe that the speed of my table was not accurate or stable at 33 1/3 rpm and the fact that it drifted all on it's own.
Then play some music and watch the Verdier slow down as the Timeline easily demonstrates. I use green painters tape, two pieces against the wall about 6 inches apart.
Quite frustrating. Did I worry about such a thing when I had the CA, clearly not. But now that I know that the speed is off, am always conscious of it. Obsessive no, but aware of it all the time. Do I enjoy music less on the Verdier, of course not but.
Have taken on the task to make a battery powered unit with a charging system like the "Callas unit" and will rewire the motor for the Verdier instead of using AC.
Hope that this will solve my speed issue on the Verdier.
My direct drive tables do not have this speed drift issue at all. Great video Halcro.
I think that Halcro nailed it in his post above.

"If you want to be happy.....use a strobe.
If you want the truth.....use the Timeline :^)"

My two cents, take care.

Dear Thuchan,
I don't use the Timeline as a record weight as I find it too light.
Therefore I use it from one turntable to the other only if I want reassurance? :^)
Cheers
Henry

Dear Halcro, you´re right the Timeline is perfect. The Allinic provides the advantage you may use it as a fixed installation and you do not need to hit the mark at the wall which is a bit of trial and error moving the Timeline forth and back - but of course after a while it works brilliantly.

You have two turntables and only one strobe - this looks like an imbalance :-)

best @ fun only

I filed the hole in my stereo test record. I improved the runout a bit. According to the iPhone app, I now have the raw Wow down to +/-0.16%. The filtered didn't change, -0.01%/+0.02%. The total spread within the published specs for my tt. With a little more filing of the center hole and more work/patient effort to center the record on the platter, I could improve the raw values even more. I have a feeling that I will be bringing a dial indicator home from the machine shop at work to measure record runout with extreme precision. I will likely be filing the holes on my records now to perfectly center them. My neurosis is ratcheting up a level, I think.
Anyway, this app is nice, you can play the test records 3150Hz track at 45rpm and this app will detect the higher frequency and tracks the speed at 45rpm automatically. I must agree having seen it live with this app. Having the motor via a belt separate from the floating chassis/platter is a deficit. The slightest vibration/movement of the floating chassis causes a speed error. It is a small error, but still there.

Halcro put it in the most precisely manner. The Timeline may be frustrating in it's accuracy, but then it is not the Timeline's fault. Very interesting too, to watch the laser beam over the whole record side ( record it with a camera - it is too boring looking there all the time).
On many turntables one may notice shifting back and forth and correction with controlled motors during heavily modulated passages.
A nice lesson in stylus drag and it's not linear nature.

My KAB strobe works pretty well also.
With it....the Raven keeps perfect speed.
If you want to be happy.....use a strobe.
If you want the truth.....use the Timeline :^)

The Allnic SpeedNic works pretty well. I have put two images on my page (last two images when scrolling down)

best @ fun only

Dover, good suggestion. I have a small, round bastard that should do the trick. I might give that a try.

Tonywinsc,

For records with holes out of centre my engineer mate simply uses a thread file ( very small round file ) to open the hole up only in the direction you need to move the record to centre it. Then puts a marker on the label to indicate which side of the elongated hole butts up to the spindle. This seems to work reasonably well.

Very interesting thread!

Obviously the question how important speed accuracy actually is and how to achieve best results challenges TT designers and puzzles music lovers like us for … as long as vinyl records exist!

Maintaining constant AVERAGE speed of 33.1/3 or 45 rpm has been accomplished, but I don’t think that AVERAGE speed accuracy is extremely critical. The real engineering challenge is to maintain constant speed at any given time in any infinitesimal small time interval. Not everyone might agree, but I don’t think this engineering challenge has yet been accomplished. Maintaining absolute constant speed against an ever changing load is … probably impossible!?

To illustrate my thoughts I would like to use an analogy.
Imagine a car rolling on uneven beams of a railroad track being pulled by an engine which in turn rides on the smooth train tracks. The car in pull is our platter, the bumpy beams represent the ever changing load caused by stylus friction, and the pulling engine is our electric TT motor. Our goal is to keep the car in pull at absolute constant speed (measured in the horizontal plane). Forces caused by the tires hitting a beam instantly try to slow down the car in pull and the pulling engine tries to work against this load change to maintain desired speed.

It seems obvious, that a strong engine is beneficial to minimize speed changes caused by load changes. It also seems obvious, that using a flexible rubber band to connect the pulling engine and the car in pull will make it even more difficult to maintain constant speed of the car in pull. No matter how strong the engine, the flexibility of the rubber band will allow the car in pull to vary the distance between itself and the pulling engine caused by ever changing forces from climbing up each wooden beam.

In this analogy the rubber band represents BD designs, while a stiff beam connecting the car in pull with the engine would represent idler drive designs. A DD turntable places the engine into the car in pull itself.

Quartz controlled speed regulation of any TT drive system requires a speed change to actually happen first, before it can be detected and in return corrected.

In contrast, unregulated A/C motors (Garrard, Lenco etc.) actually don’t try to maintain constant speed. If we ignore that our rotating system has a mass, the resulting platter speed of an unregulated A/C motor drive system becomes a direct function of the applied friction. The absolute speed change resulting from a load change depends on the steepness of the torque-speed curve of the electric motor in the area of operation.

The link below shows several characteristic torque-speed curves of induction A/C motors (Figure 9).

http://inductionmotor.co.in/shaded-pole-ac-induction-motor.html

The famous vintage idler drives (Garrard 301/401 and Lencos L75/78 for example) use shaded-pole induction A/C motors (curve on bottom).

I did some measurements on my own Garrard 301. When working against friction caused by the platter bearing as well as needle drag, the motor operates at about 99.6 % of no-load speed (very close to the right end of the torque-speed curve on the chart). Only the steepness of the curve in this area determines the resulting speed change from a certain load change (increased bearing friction from additional weight on platter for example).

Accepting the fact, that achieving constant speed is literarily impossible, the real question to me becomes, which design approach results in sonically more acceptable speed changes caused by the constantly fluctuating load from needle drag.

The regulated drive system requires a speed change to occur first to detect and correct the speed by applying more torque. In an unregulated A/C system speed changes also occur, but no mechanism tries to correct the speed back to the desired nominal speed. Both systems accept small speed changes as a result of load fluctuations.

Even if we were able to precisely measure these extremely small effects, IMHO only our ears can judge which type and characteristic of speed change is more acceptable to our hearing. The mix of compromises that each design comes with and the effect of all of these compromises to our hearing determines what type of drive system is able to produce most pleasing results.

I went thru my own little try and error TT experience and am by far no expert on TT designs. What I do know though is (even though IMHO none of the existing designs achieves it) that absolute speed accuracy is of utmost importance to the musical presentation. The sonic difference between low and high torque drives needs to be experienced to understand the impact to the musical presentation.

I’m currently using a Garrard 301 with Loricraft’s large PSU providing 220 Volt and 50 Hz to the Garrard, which – compared to driving the Garrard with 110 Volt at 60 Hz, using a smaller pulley – “steepens” the motor’s speed-torque curve in the critical area close to no-load speed.

No matter what drive system is used, I’m convinced that a high effective torque drive is a must, and that any flexible element able to store energy between motor and platter will work against the goal to minimize speed changes from load fluctuation.

I found TT information on Arthur Salvatore’s webpage very interesting - especially his idler drive section.

http://www.high-endaudio.com/RC-Tables.html

when it comes to bearings/ motors and platters I see a difference between the vintage designs and most of the modern turnables. The  service principles say I need to lubricate the EMT' s bearing every year, oiling the motor once in years. Introduced in 1951, the EMT 927 is a massive turntable with an aluminum chassis,  meassuring  6 7. 5 x 52 x 21 .5 cm with a weight of 80 pounds. The platter has a diameter of 44 cm and sits in an amazing precision ball bearing. The bearing shaft is 16.6 cm long and has a diameter of 2 cm! The motor itself is massive. It looks like an industrial motor, 13.5 cm in diameter and 20 cm long! It is a 3 phase synchronous type with phase shifter.

The big MS designs have an oiled, capsuled bearing which should keep a man's life. The massive platters have a weight of 40 to 50 pounds, the full table up to 170 pounds. The Micro Seiki motors are very precise (with a competent controller) as the Continuums motor is as well, a linear 3 phase AC-24V DC Brushless design with integral optical decoder. You need looking at these parts to get an understanding why the usual small motors used for todays TTs are a joke! The Continuums platter has a weight of 60 pounds. I have put an image of the self lubricating bearing on my page to show the difference.

I do understand when Dertonearm questions the quality of new developments against the Micro Seiki, EMT or Continuum standards. In all the mentioned designs the mass does its job with inertia and resonance control. All that makes for a very good turntable in my opinion. And in all designs precision is of importance. 

best @ fun only

Bearing lube for dd turntables is yet another controversial subject. Fortunately, the rotation is so slow and relatively low stress that almost anything will do to prevent bearing damage. One guy who restored my L07D insists on only a certain weight of a certain racing motor oil. I am sure it is overkill.

I found the owners manual online for Adjust+ and some reviews. As I surmised the low pass filter is set for 0.56Hz to eliminate record runout. I was considering drilling the center hole out a few tenths of a millimeter on my test record, but I began imagining what a catastrophe that would be me loose with a hand drill with one of my precious records. Fortunately this iPhone app cancels out the record runout for you. Pretty cool app.
Regarding the tt bearing: I do my own maintenance on my tt. Periodically I breakdown the tt and clean the main bearing. I re-lubed last time with a synthetic grease. I think it made the tt sound better. Anyone else had that experience? I have never touched the motor.

Dear Lewm, disagree. I think they read the posts but they understand it in a different way as you, me or others do.
This is not because they not only have a more sensitive scope but maybe they have a more sensitive feeling too when reading each other`s post.

Nevertheless I do think in this topic we are all not far away from each other. We all agree that accurate speed is an important condition or precondition for enabeling a good sound quality.

Of course there are other factors having also an impact on good sound quality, the bearings quality (e.g. air based or other quality attributes), the motor´s quality (maybe also fly wheel or more motors), the platter`s quality (material, weight, air lips) the belt, thread or idler wheel`s quality, and last not least the interference and the implementation of all these turntable parts. Enough stuff for some more threads...

best @ fun only

It seems like none of us read each other's posts, except Raul and DT, so that they can reach immediate disagreement. A century ago an American writer named Ambrose Bierce defined "conversation" as a social interaction wherein I wait for you to finish talking so I can say what I want to say. In any case re turntables, DT is right. The first job of a tt is to get speed right. Raul used to argue that a phono stage that does not do riaa within 0.1 db is fatally flawed. You can't have it both ways, Raul.

I downloaded the iPhone app and did some testing. The same test record that I used before also has a track with 3150Hz. As I mentioned before, I measured considerable runout in my test record which by itself causes some audible Wow when playing constant frequency test tones. The center hole of this test record has a slight amount of play on my tt spindle. After much patient work to minimize the record runout I got the following measurements: Mean Freq: 3151.3, Raw Frequency: -0.22%/+0.24% relative, -7.0Hz/+7.4Hz absolute. Lowpass Filtered Frequency: -0.02%/+0.01% relative, -0.5Hz/+0.5Hz absolute. I'm guessing that the filtered values subtract out the record runout. The reason I conclude that is as I meticulously adjusted the record on the platter to minimize runout, I had raw numbers as high as -9.8/+10.7Hz while the filtered values never exceeded 0.03%.
Another observation: The original Mean Freq was 3155.6Hz based on my setting using the strobe disc. I adjusted speed down and can certainly work some more to dial it in at precisely 3150Hz. The other observation is that holding the iPhone while taking the measurement adds more error. It is sensitive enough to pick up hand movements. I set the phone on a table about 1 meter away from the front of one speaker.
So how does my humble BD table compare to some others?
btw- I have a record clamp. So I adjusted the record relative to the spindle and then clamped the record down.

From what I can see and read about the Speednic......it seems no different to a Kab strobe?
Can anyone explain to me how the Speednic competes in any way with the Timeline?

Dear Thuchan, the Speednic by Allnic looks neat. Especially as it allows adjustment during play and thus taking into consideration stylus drag.
Thank you for the hint.
Cheers,
D.

Speed accuracy has inspired two more companies bringing out devices for checking. Allnic with the SpeedNic turntable speed checker and Dr. Feickert's free Platter Speed speed check software (for i Phone or Android) - learning from MF...

best @ fun only

I am not assuming that the main requests are all there, - in fact I see that in many cases this is just not the case.
The request itself is nevertheless a conditio sine qua non in the context of the technical blue book of ANY turntable.
That reality in many instance doesn't follow the request doesn't mean the request is wrong.
Mediocrity may be the name of the game with few exceptions.
It never was for me.
To me it is always and only about best possible results - not was a majority may have problems in nor whether a majority of components may have problems with.
IMHO speed accuracy is so basic a request by nature for a turntable that it is not worth discussing at all.

Dear Dertonarm/Syntax: +++++ " However IMHO speed accuracy is a basic - if not THE basic - request to ANY turntable.
As said before - this is a conditio sine qua non for any turntable.
As this is a basic feature, it is not contributing to the sound quality.... " +++++

IMHO that statement is plain wrong: it is as to say that a phono stage " basic request " is no RIAA deviation/gain with no noise or in an amplifier 0.01 ohms output impedance or in a cartridge flat ( cero deviation ) frequency response or whatever with any kind of audio items.

The premise that those are " basic request " audio device in the designs does not means the audio product already achieved only because are " main request ".
In our imperfect audio world there are almost none of that " main requests " in any design that fulfil those main requests.

So to assume that main requests are all there is IMHO a wrong assumption.

TT's is only an example both of you can take any audio item and you will and know that the " majority " does not fulfil even those main requests. Mediocrity is the name of the game with a few exceptions.

Now, speed is only one factor in the whole TT design and in the final quality level performance.

We will see how good the " main request " on a TT: neutral/accurate can be match by all those new designs including yours.

Regards and enjoy the music,
R.

Funny thing that as soon as a NEW component - which none here has heard nor seen in real life so far - isn't praised ahead it is "diminished".
It is not.
It is just not praised ahead and there is nothing new displayed.
Simple.
Some will buy it - some won't.
It will eventually earn some laurels and I will most likely be one of the first in the western hemisphere seeing and listen to it.
Turntable designer disclaimer ...;-) .....

Dear Raul: If one has built a turntable than which none greater can be conceived, then there's no need to listen to others, except as a form of idle amusement.

Dear friends: Do you think here could exist speed accuracy?

https://picasaweb.google.com/hfeiner/TWOTURNTABLES?authkey=Gv1sRgCOy02-j1puykKA#5678170499062229282

that's is a JC/TH/H contribution.

Regards and enjoy the music,
R.

Dear Dertonarm: Like with the Wave Kinetics and Onedof new TT designs now you follow dimish every new TT design like this one Air Force One.

Why in one way or the other do you want to dimish the other designers efforts even when you never heard those new designs?
I can't see any other TT designer that already dimished your coming TT?

We customers need alternatives and with out real and precise foundation why comment/dimish/attack a new TT design what/that you never heard it and never has on hand?

I know that your design is wrong but I don't care about because is your design not mine.

Regards and enjoy the music,
R.

it is very funny, the DD-drive concept divides the users in two seperate fields, lovers and deniers, as sometimes happens with the idler drive as well. From my experience with DD drives I am convinced that a DD motor needs a perfect environment (sorry Halcro). There are excellent examples of "very musical drives", e.g. the Technics MKIII in a fine plinth, the Nakamichi (Micro Seiki motor) or the Brinkmann Oasis.

I found an interesting description at Brinkmann maybe with relevance to the speed/time issue:

The drive mechanism is probably a turntable’s single most important component. This significance results from the fact that music consists of sounds organized in time. A turntable therefore has to play back a record at precisely the same speed at which it was cut, normally 33 1/3 or 45 rpm. Any deviation, no matter how small, from the correct speed will ultimately change pitch and tempo and result in music reproduction that is not true to the recording.

Our hearing is much more sensitive to short term speed variations, as opposed to long term ones. The onomatopoetic term wow & flutter correctly identifies the underlying issues— wow describes continued, longer lasting deviations, caused for example by eccentric records, whilst flutter denotes short-term irregularities best demonstrated by piano tones that fade away with a slightly howling quality.

Let us consider the following example: a 1 kHz tone (1000 cycles per second) is cut into a lacquer at precisely 33 1/3 revolutions per minute. If the pitch is to be accurate, the turntable has to play back this tone at exactly the same 33 1/3 revolutions per minute. A seemingly insignificant variation of 1% would result in a playback speed of either 33 or 33@d revolutions per minute with pitch being off by ±10 cycles. Even people with perfect pitch would have a hard time correctly identifying a 990, 1000 or 1010 Hz tone without a reference— yet even “brass ears” would easily hear the differences in a direct comparison.

Speed precision is perhaps even more important for the music’s tempo. For our perception of music to be real, the tempo—timing and pace—is more crucial than the pitch. This is where the 1% difference would make itself heard far more easily. Considering that a typical record has a playing time of around 20 minutes per side, a ±1% difference would amount to no less than 24 seconds. This seemingly irrelevant deviation would result in either a slightly restrained and darker sound, or a livelier, brighter reproduction of the original event.

In order to meet the claims of High Fidelity—no more, no less than music reproduction true to the original the cutting and playback speed have to be absolutely identical. Due to reasons being outlined in the following pages, this theoretical ideal is practically not feasible—turntables are hence (and in the best case) the closest possible approximation to the theoretical optimum.

Two elements determine the rotational speed of an AC based electric motor: the power line frequency and the number of magnetic poles. The formula used to describe this is as follows: rotational speed = line frequency x 120/number of magnetic poles. In countries with a 60 Hz power grid, a two-pole electric motor therefore runs at 3600 rpm (60 x 120/2 = 3600). Each doubling of magnetic poles cuts the rotational speed in half: 4 poles equal 1800 rpm; 8 equal 900 rpm; 16 equal 450 rpm. Theoretically this could be continued even further, however, practically, there are only so many poles one can fit inside a motor case.

Further, each additional pole also increases the motor’s torque, which in turn increases the cogging effect. DC electric motors don’t fare any better either and most are offered in standard 1500 rpm configurations. This showcases the ensuing problem quite easily: on one hand we have an electric motor spinning at 1500 rpm, on the other we have a platter which has to spin at 33 1/3 rpm. The ratio of motor to platter speed is therefore 45:1. Logic dictates that the drive pulley has to be 45 times smaller than the platter.

If we take a platter diameter of 30 cm as an example, this would equate to a pulley of only 6.6 mm in diameter. The contact area for a belt is therefore very small, which in turn increases slippage; which in turn influences speed stability negatively. The problem is further exacerbated by the fact that the cogging is transformed into a frequency range in which human hearing is very sensitive…
The power line frequency (and thus the motor’s rotational speed) can be reduced with frequency converters; however, the cogging problem still persists.

The platter of a turntable can either be driven directly or indirectly. In case of an indirect drive mechanism, platter and motor are two separate components whereby the power from the motor is transferred to the platter through intermediary means. In case of a direct drive turntable, platter and motor are assembled into one and the same unit.

Motor and platter are two separate entities; some sort of medium is necessary to couple the motor to the platter. Typical applications include the following:

> Belt (round or flat; geared or v-belt type; various threads made of synthetic or natural fibers)
> Idler wheel
> Gear wheel drive

The choice of transfer medium is critical since it not only transmits the motor’s torque to the platter but also all motor-based interferences, among them the motor’s cogging, which compromises speed stability since the platter is not driven continuously but somewhat jerkily instead. The more direct the connection between platter and drive, the more directly these interferences will be transferred. An idler wheel for example couples the motor very directly to the platter. As a result, the cogging effects are more pronounced; in the best case they manifest themselves as a slight flurryness of the sound; in the worst case through clearly audible distortions.

Because of the reasons stated above, most turntable designers therefore prefer a softer coupling between the diameters of the motor pulley and the platter. Even tiny discrepancies in the belt’s uniformity will have a serious impact on the platter’s speed stability. Consider the following example: say a DC motor running at 1500 rpm drives a 20 cm sub-platter via a 1 mm thick flat belt. A discrepancy in tolerance of only 1/100 mm will have a net effect of 0.9% wow & flutter on the platter!
Countering these effects demands substantial efforts in the design of a belt driven turntable. Heavy platters (12 kg or more) and low rpm motors tend to mitigate these side effects to the point of not being significantly audible.

Studios (radio stations in particular) demand quick start-up times – turntables typically have to reach their correct speed within half a revolution. For LPs this means 0-33 1/3 rpm within 0.9 seconds. Such acceleration figures can only be achieved through use of high-torque motors and correspondingly tight coupling between the drive and platter. It isn’t a surprise then that for decades idler wheel drive designs were the de facto standard in studio applications.
But idler wheel turntables also had seriously high maintenance costs in order to be up and running 24/7 and to avoid rumble and other sound degrading issues caused by worn out idler wheels to affect the sound negatively.

Thus out of necessity, in the late 1960s manufacturers of studio turntables began to look for
low(er) cost maintenance alternatives. They came up with direct drive, whereby the platter was placed directly on the motor’s shaft, ie the stator was mounted around the bushing and the shaft was used as the rotor and voila, the goal was achieved; at least in theory.

But start-up times of less than 1 second necessitated high torque motors, which designers achieved byusing motors with 32 and more poles. The penalty they paid were heavy cogging effects accompanied by high wow & flutter numbers. The cure was found in quartz locked motors and phase locked regulators; which corrected for any deviations from their preset with an iron fist.
On paper at least, these “corrected” direct drive turntables boasted hitherto unimaginable low wow & flutter numbers down to 0,001%. But the rigorous iron fist regulation prevented the platter from spinning smoothly; instead, the regulation caused the platter to oscillate continuously between speeding up and slowing down.

These start/stop motions translated into an unpleasantly rough and hard sound; odd as wow & flutter numbers in the 0,001% range are deemed inaudible. Once the direct drive technology had gained a foothold in pro audio applications, the benefits of mass production (ie. trickle down effect) made sure that very soon even $100 turntables were equipped with direct drive and advertised as having less than 0.01% wow & flutter. This is precisely where direct drive got its bad rap sheet.

Under closer scrutiny however, this assumption were based on some misunderstandings. For one, in home audio application use, turntables are not really required to reach 33 1/3 rpm in less than a second, thus 32 pole motors and phase locked regulators are not really necessary either.

Finally, one more relatively unknown factoid: while it is common knowledge that direct drive turntables became popular in the late 1960’s, their actual invention dates back to a small Swiss manufacturer in 1929. The name? Thorens, who enjoyed and even today is looked upon with great respect for their idler wheel and belt driven classics.

Dear Thuchan, if you are referring to the TechDas as "Micro Seiki back", I wouldn't go that far.
IMHO that design does not resemble Micro Seiki engineering.
We will see what is actually delivered, but what is apparent in the pictures and short descriptions so far doesn't break any new grounds.

Dear Nandric,

it is an ongoing quest. I am happy that some new designs appear on the horizon and that Micro Seiki seems to be back.
Maybe we will not see only clouds in the future...

Best @ fun only

Dertonarm, Thank you.

In_shore, sure - speed accuracy does heavily influence sound quality.
However IMHO speed accuracy is a basic - if not THE basic - request to ANY turntable.
As said before - this is a conditio sine qua non for any turntable.
As this is a basic feature, it is not contributing to the sound quality, but only in negative sense - i.e. if not accurate speed.
So - here it starts, it is not a goal but the mere basic request which has to be meet by nature anyway.
I as a designer simply make sure this demand is meet to the utmost possible as the very first step.
And I for one think this is easy given today's technical tools and options.
Accurate speed can be obtained with idler wheel, direct drive or thread drive.
It can be achieved with belt drive too, but only with much more effort in control.

Dertonearm
If speed accuracy has nothing to do with sound performance but is a seriuos basic request with a design then where would you as a designer place it in order of importance if all else is managed in a design of a turntable?

In other words if the motor/s, speed controller, belt/s are not up to the job holding the speed when a record is being played would this not drastically effect what you hear?

I am listening (... reading ...), Halcro ...;-) ...
Just back from California and Texas and haunted by 9 hours jet-lag.
Will get the "secret rope" off to you on friday.
Sometimes less is more.....

I discovered that removing one of the three motors of the Raven AC-3 (aka Raven AC-2)......the turntable was able to maintain far more accurate speed control than with the three motors.
Perhaps the belt stretch or slippage is increased with the three motors?......or the greater contact of the belt on the platter with two motors is the reason?
I can't wait to try a Bavarian thread in place of the rubber belt?
Are you listening D? :^)

Dear Thuchan, Our German friends are obviously searching for the new or added preconditions which are yet not known.
If they were known and technicaly solvable then probable
there would be no or less problems with those damn TT's.

Regards,

Deartoenarm,
agree with your preconditions being set. Unfortunately the reality regarding some running tables looks sometimes different due to weak motors, belts changing the consistency, no built in or used precison control instruments etc. The new TechDas AirForce seems to offer some nice features. On the other hand I would have wished a two sided belt driven system.

best @ fun only

Dear Thuchan, Syntax' comment on "sound quality not related to speed accuracy" points to the fact that the sound quality per se is not in the speed accuracy.
Speed accuracy in a turntable is an undisputed conditio sine qua non.
If a turntable isn't able to hold the 33 1/3 (and the other speeds required..) it isn't worth discussing about sound quality at all.
In the first shoot out in San Antonio between a serious DD and a serious thread drive turntable, we all 3 - Unoear, Syntax and me - heard that there are sonic qualities which go way beyond speed accuracy-related phenomenons.
Speed accuracy is a basic request for any serious turntable.
Here it starts off - it certainly doesn't end here, it is rather the beginning.

Sometimes threads do accidentally get 'wiped' by an administrator.
It's happened to me twice and when I contacted A'Gon ........they retrieved them.
Have you tried that?

Thuchan,
I don't know what happened to the Wave Kinetics NVS thread. I enjoyed that thread because with such a new design, there is very little information in the popular press, so forums like these can be very helpful.

I started this thread because that NVS thread was going off topic and becoming a discussion about speed stability and different drive types. I wanted it to go back to its original focus. And yes, this thread is wonderful and I've learned a lot about the topic of speed, how to maintain it and how it effects the sound.

Threads have a way of disappearing and it is not always by accident. I have no information. Perhaps Jtinn knows something.

Peterayer,
I could not find the Wave Kinetics thread anymore too? Sometimes it happens that a thread disappears by accident. Do you have some information? You suggested this new wonderful thread.

best @ fun only

Dear Syntax,

you are saying speed stability has nothing to do with sound quality. How do you mean this? If the speed is varying enormously during the playback process it leads not only to deviations in wow & flutter but you can also hear an impact on the sound, I mean I can hear it. And I believe you do too !?

best @ fun only