Why three motors?



Can someone enlighten me on the wisdom of having a three motor turntable like the TW Acustic with only ONE side of the belt touching the platter?

Here is an example.

I just don't get it...
hiho
Whatever variations, irregularities, etc. in one motor are averaged or even canceled out by the other motors. It should lead to better speed stability, both long and short term.

Sorry, I should have asked the question differently. With three motors, why have ONE side of the belt touching the platter? It's the belt arrangement that I question. What is the point of that? With two motors, side torque is eliminated or equalized so the platter bearing is not pressured towards one side. In the TW Acustic, it appears at least to me, the whole thing is an afterthought on cashing in on selling more motors and the original plinth design was not intended to have three motors to arrange the belt in an equilateral triangle so all three sides of the belt can touch the platter. Instead, the arrangement end up having only one side touching the belt. Wouldn't two motors be better in this case? What I see in the picture is bewildering to me. Am I missing something here? Please illuminate me.

The latest Raven turntable abandoned such scheme and opted for three motors in a single housing, which is also questionable in itself.
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the two arms is probably to be able to do a reverb if you manage to drop them slightly simultaneously having a 4ch phonostage... just kiddin'-)
The way it is arranged in the photo does look a little odd. Any idea what the tonearm with the wooden armpipe is?
This is typical german engineering. If one motor fails you still have instant replacement on hand.....
Please illuminate me

Simple answer: That's Higher End

*Sad* Personally I feel discriminated with a 1 motor Design.
This is typical german engineering. If one motor fails you still have instant replacement on hand.....
06-07-10: Dertonarm

Dertonarm,
Drag of the dead motor would have to be made up by the other two motors.

Hiho,

Did you find any manufacture literature on the TT?

With three motors, why have ONE side of the belt touching the platter?
06-06-10: Hiho

Agree.... All that motor HP available and so little belt to platter contact.
Hello Jea48, these motors in the TW Raven are so good, that they won't have any problem with one dead fellow (which in turn would have no friction if he should ever fail - which I can't believe would happen anyway). If one dies indeed, I am sure that this would literally went unnoticed.
It is typical german (over)-engineering.
That strange arrangement with the one side belt in tangent contact only must have a sonic benefit.
I am sure and confident, that this is a feature of the original design.
Ok, my understanding in layman term, the belt will somehow suck the life out of the music. So the least the contact of the belt with the platter, the better. I owned Raven AC with one motor and in the process of ordering the 2nd motor.I also believed the two motor setup is more balance.

Regarding the Black Knight, the position of the motors have better grip with the belt. Who knows, Mr Thomas might come up with another set of motors on the other side of the plint in the future.
I have a Transrotor Apollon with three motors but the arrangement is different. The belts actually fit on a grooved slot on each motor that corresponds with a grooved slot on the magnetic bearing assembly on the bottom of the platter. My platter is really heavy, 80mm thick polished aluminum and three motors helps in regards to maintaining speed accuracy, timing and just the sheer grunt to move such a heavy platter.

Onhwy61 said it best: "Whatever variations, irregularities, etc. in one motor are averaged or even canceled out by the other motors."

It should lead to better speed stability, both long and short term. Never had any noise or vibration issues from the three motors. All I know is that with one belt, the platter spins up to speed a little longer with a nudge, but with all three belts, the platter is under absolute control of the belt grips and they belts take control and you KNOW there is more torque grabbing the platter.

I think it would be the difference between a kid spinning a "merry go round" versus Hulk Hogan, Mr. T and The Hulk, yeah that is it.

Anyway, voiding any disparaging comments from the technical aspects concerning pros and cons of having three motors; the three motors I have work great for me and the sound is incredible.

Thats my story and I am sticking to it.
Ciao,
Audioquest4life
T_bone: "Any idea what the tonearm with the wooden armpipe is?"

It's a German tonearm made of ebony.
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One of the explanations about the belt arrangement I read is that it simulates an idler wheel with low contact area. If that's the design intention I found that unconvincing. The three motor set up with such belt arrangement has been discontinued by the manufacturer so I have to assume the designer no longer endorse such approach.

Here's a lively discussion about the design.

Again, I found the belt arrangement to be half-baked until someone can explain it to me otherwise.

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Various three motor turntables in different belt arrangement, either single belt or triple belts and all of them have the platter touching THREE sides of the belts.

Audionote

Transrotor

Clearaudio

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Hi Hiho, well - thanks for posting those three 3-motor-drive contenders. They all share the very same set-up - as far as geometry goes. All using a 3-side-symmetrical approach. Somehow logic and going along with the common sense of mechanics in providing a force-vector free bearing in the horizontal plane. I guess we still haven't found the true idea behind the Raven's 3-motor-drive.
I have read a thread in the past Clearaudio with 3 motors sounded best with only 1 belt. this guy has experimented with all possible configuration and found the sound to improve significantly with only 1 belt. his hypothesis was 3 motors + 3 belts variation is higher than 3 motors + 1 belt variation, therefore using 1 belt vs. 3 reduces the overall variation produced by the drivetrain. YMMV.
I really should have changed the titled question from "Why three motors?" to "Why such belt arrangement?"

I am less interested in why using three motors but in why they arrange the belt in a 3-motor design that only one side of the belt is touching the platter.

If they use four motors, the belt would not touch the platter at all! Perhaps that's the best sound in having the blackest background.

Syntax: "Simple answer: That's Higher End"

So far that's the best answer.

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When I first saw such a turntable, the arrangement of the belt struck me first, and I admit not particularly considering the motors. Now that the question has been properly framed, I don't really understand the principle of three motors, but I do get the belt arrangement. It does have something in common with an idler in that it mandates a smaller contact area with the platter, or footprint. This may in turn alleviate belt creep to some degree, and I have come to believe that belt creep affects micro dynamics by smearing the music at a subtle level. It is one workaround, but other belt drive makers have other ways of accomplishing the task.

A notable example is the Artemis Labs turntable that Frank Schroeder designed. It uses a spring loaded pulley to help control belt creep, and at the same time it serves as a noise canceling device of sorts. A less sophisticated solution was found on the 1962 Rek-O-Kut Rondine 2. Yet another solution can be found in the Spiral Groove turntable. Its drive is configured in an optimal way that helps isolate noise and reduces the effect of creep by various positioning maneuvers.

It has occurred to me that a single motor with two equidistant pulleys might be an improvement over traditional schemes, but I build idler turntables, so I'm not a candidate to try the idea. However, a lot of you have belt drives, and are handy enough to make the modification. If one of you actually does, it may be something interesting to others.

Thanks for your idea about the belt arrangement. But I seriously doubt the designer intended that way and if he did, that's a rather belabored effort to achieve small contact area by using THREE motors and not to mention belt slip. Oy! Why not just use an idler wheel? The manufacturer no longer has that model so I have to assume they have changed course.

There are formal reviews of the turntable and yet not one reviewer questioned the wisdom of the belt arrangement; they are the usual couple paragraphs describing the mechanics and they go straight to the epic flowery prose about the soundstage blah blah blah.

Your examples of combating belt creep is very interesting though. Thanks.

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Well, thank you. I do build idlers because of some predisposition that I have. Bear in mind that ours is a hobby of flavors, though. Still, I am intrigued by different approaches, whether they be three motor belt drives or massive string drives. After all, there is more than one way to skin a cat.

Win
Saskia Turntables
Gents, let me explain,this is a very compex response so read carefully.

Thomas did something that was amazing. He listened to one motor, two motors, 3 motors, multiple belts and came up to the conclusion that 3 motors with one belt sounded better. Thomas quoted.

" The three motors give you a more relaxed sound. All instruments and vocals are better imaged. They just take you one little step closer to live music."

BTW, I have no idea why 3 motors sound better.

Hey Dertonarm
I almost fell off my chair. 3 posts about TW and not one negative jibe. You must be in therapy or something :-)
Hey Downunder, it is very simple: I have finally realized how great all TW-products (past, present and future) are.
Given the fact (which many fellow A'goners here discovered before...) that I am slow and rather simple-minded, that came somewhat late to me. But now I am convinced. The 3-motor-drive/one-side-belt-touch-only was the very last drop I needed. When I realized the striking idea and empirical research behind it, I was stunned in awe.
That's what I tried to express in the past posts in this thread.
Syntax too is already desperately looking for 2 more Micro Seiki RY5500 motor drives to finally enter Nirvana. Problem is, those motors are too large to fit in the spaces between his armbases and the rack is too small too.
Anyway - neither him nor me will turn on our front-end again before adding more motors to the set-up. I will check back with my Lancia whether I can't add 1 or 2 more motors to make the drive more relaxed and to add further presence to the drive experience.
This is audio, and not everything can be measure. Before the TW I owned the one with ceramic magnetic bearing. And my perception was TW could never beat it in this aspect.A no contact floating spindle. I bought TW because it's massive, beautiful, black...And what, TW sound way, way better,and I'm using the same tonearm, cart...Btw I never heard of Caliburn, Walker and Transrotor.
Gents, let me explain,this is a very compex response so read carefully.

Dear Downunder, thank you very much for your insight and warning. It is indeed VERY complex, I read it carefully AND very s-l-o-w-l-y.

Probably that Pic from the Raven is an old one, guess Raven Mk 33.3, you see it, that the belt is stretched. The later generation has one with higher specs (but I am not sure). But it saves the owner some money, he pulls away the motors and can use it some more time. Great. This German knows what the Audiophile needs.

When I realized the striking idea and empirical research behind it, I was stunned in awe...

Yes, never too old to learn from a real Master.
Some time ago I made comparisons with Belts, I got some very interesting results, but when I see this fascinating solution, I think, I missed the target by a mile.

Belt Comparison

... is already desperately looking for 2 more Micro Seiki RY5500 motor drives to finally enter Nirvana. Problem is, those motors are too large to fit in the spaces between his armbases and the rack is too small too.

Well, well, here you see my experiment for the

sonical Nirwana.

"Thomas did something that was amazing. He listened to one motor, two motors, 3 motors, multiple belts and came up to the conclusion that 3 motors with one belt sounded better."

You skipped the process of him listening to THREE side of the belt touching the platter, and then TWO sides, and the finally ONE side to reach nirvana.

I have nothing against TW, it could be a different brand and all I saw was a turntable with a rather curious belt arrangement that I never saw before so I asked a simple question. Why? So far no convincing answer. Even more curious, is that the manufacturer no longer have such configuration. And I have to ask why again. Was it a flop and had to change course again? Are those 3-motor turntable owners still sticking to that belt arrangement? If change, what do you do with the extra motors?

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@T_bone

That is a Shroeder tonearm
Which Shroeder would that be?

Hey Dan,

There were two links posted by Hiho showing a wooden arm. In the second one (3rd post) the link "Titled TW Acoustic" links to a picture of the table with a DPS on it. The original post has a link to a different picture with an wooden arm on it that was later identified by Hiho.

dave

FYI, I posted two images of the Raven turntable, each with two different tonearms.

1st image with Analog-Tools 12" tonearm and Audiocraft AC-4000 12" tonearm

2nd image with Schroeder DSP 9" tonearm and Dynavector DV-507 9" tonearm

Both turntables have three motors with only one side of the belt touching the platter.

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As a recent convert/owner of an AC1 I too am mighty curious and sceptical. There are some A'goners who have traversed the 3 motor route. Would be interesting to hear from them.
Loved the wooden armboard in one of the pics. Can it be ordered?
Cheers
Hiho said - "Even more curious, is that the manufacturer no longer have such configuration. And I have to ask why again. Was it a flop and had to change course again? Are those 3-motor turntable owners still sticking to that belt arrangement? If change, what do you do with the extra motors? "

Where did you get that information from??. The AC is available as a AC-1, AC-2 AC-3 (1,2 or 3 motors) and with the Black Knight motor.
He also orders the battery power supply from the black knight on the AC if you want it. I preferred the standard motor.

Exactly where has TW changed course??
Thanks Dave and Hiho. I was indeed looking at the first picture.
Hello Sunnyboy, seen your setup. Why not use the short belt?
Yeah, Hiho did alarmed me. For a while, I thought my 3 months TW Raven is obsolete.
I have never listened to any of these 3-motor tables, but the configuration shown, where the belt contacts the platter on only one side of the "triangle" would seem to be a worst-case set-up for "belt creep", as first described (to me) by Mark Kelly on Vinyl Asylum. In fact, to minimize belt creep, the belt should contact the platter over as much of its circumference as possible, e.g., the pulley of a single motor should be snug up as close as possible to the edge of the platter. Or you can use a capstan-like extra pulley to keep the belt in contact with the platter a la the Artemis turntable. (I think that's the one with the capstan. Could be wrong.) Other solutions or ways to at least ameliorate belt creep have been proposed but are not commercially available. But 3 motors makes no sense to me.
Donwunder: "Where did you get that information from?? Exactly where has TW changed course??"

I have seen the 3-motors version on their website before and now it's NOT listed on their website - http://www.tw-acustic.de/engl/turntables - so I made an assumption that they are not offering that anymore. I apologize for not making that clear earlier. But why is that option not on the website anymore, just curious? Let's say they didn't change course, the question remains what is the engineering reason behind such unconventional approach. Any suggestions for the discussion?

Speaking of 3 motors, their flagship Raven Black Night uses 3 motors in a single housing with THREE pulleys, which in itself a curious design. Is it to increase triple the torque and/or to combat belt slip or belt creep, etc?

Lewm: "the configuration shown, where the belt contacts the platter on only one side of the "triangle" would seem to be a worst-case set-up for "belt creep"...... 3 motors makes no sense to me."

Lewm, perhaps you can get some hint from their writing about the Black Night, if not the AC3:

"Thanks to the three-motor drive and the battery power supply, the Raven Black Night does its job with poise, serenity and composure, yet just like the other TW-Acustic turntables, it is highly dynamic, involving and rich in timbre. The Raven Black Night is incredibly musical, its spatial presentation is so three-dimensional and tangible that the music is always reproduced with the utmost authenticity."

You see, it just does its job.

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I am completely ignorant of the engineering principles that govern "poise, serenity, and composure". In particular, I am weak on the subject of serenity.

Seriously, the tables in question are probably superb sounding. I mean to cast no aspersions. Here we are talking about the why of it.

About the TW website, what I meant is that I didn't see the listing or any prompt button for the AC3. As seen in the picture, obviously they still offer the three motor option. Once again, I apologize for the confusion and my carelessness. Yes, TW STILL makes a 3-motor turntable with only one side of the belt touching the platter. Below is description of the system:
Three-motor drive for Raven and Raven AC turntables / Technical details:

Our three motors run absolutely syncronous thanks to a sophisticated motor control
The diameters of the drive pulleys are accurate to within half a hundredth of a millimetre
The drive belt thickness is ground to a tolerance of one hundredth of a millimetre

We have taken the advantages of our unique drive system to the limit and have developed a three-motor drive for the Raven One and Raven AC. We have achieved perfect syncronicity between all three motors with our new, highly developed motor control system.

The extremely precisely machined drive belt, coupled with finely toleranced and matched pulleys give the concept the optimal basis for the precision we demand. If you were of the opinion that the Raven's drive system was unique, then of course you were right! But the new three-motor drive picks up where our unique single motor drive leaves off. The Raven or Raven AC is now available as a three-motor version. Of course, any existing Raven One or Raven AC can also be upgraded.
There's no mention of the belt configuration. Can we get back to the why now? Anyone?

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Mesael
Am curious about the short belt. I thought the manual says a min/max of 310mm to 320mm distance between the spindle centre and the centre of the motor housing. Is the short belt available from TW or elsewhere ? Are there any sonic benefits? Would love to use a shorter belt as my AC1 barely fits on my HRS S1 platform. That explains the diagonal fit of the AC1 if you view my system.
Sunnyboy, TW has short belt for AC1. When used, the motor is just 4mm from the plint. With it, you can position your TW squarely on the HRS platform. But the long belt would have larger contact area with the pulley.
As I understand it, you are better off with the motor pulley as close as possible to the platter, so the belt contacts as much as possible of the circumference of the platter, to minimize the phenomenon of "belt creep". I don't know why these and many other very expensive high end turntables place the motor at such a great distance from the platter, unless it is to minimize the transmission of motor vibration to the platter via the belt. It's yet another Catch-22.
With a rubberized O-Ring you could have more of an issue with motor vibration (and belt "boinging") being transmitted to he platter. This becomes minimized significantly whn you use a silk string, or tape to drive the platter. There is a noticeable improvement in PRAT and a much clearer sound over rubber.
Sorry - hit send too soon.

However I'm not certain that you would get adequate "gription" with either silk thread or taps in a 3 motor version. There's just not enough surface area on them for such a small contact area on the platter.
Sunnyboy, the footprint for TW short belt is 530 X 400mm. If from plint cones to motor, 500 X 400. You better double check your HRS first.
Mesael said:

*Before the TW I owned the one with ceramic magnetic bearing..... And what, TW sound way, way better,and I'm using the same tonearm, cart...*

Dear Mesael,

a) Could you clarify which 3 motor Clearaudio TT you have replaced with a TW?
b) Could you also share with us the tonearm and cartridge you have used in both?

Many thanks in advance
Dear Kostas,

What I have is CA Ambient with CMB bearing, and TW AC1, both have only one motor.

I'm using Moerch DP6 with CA Stradivari catridge. The switch of CA 33/45 malfunction, and have to send back to manufacturer. So I got TW, and transfer the tonearm and cart to it.
Measel
Many thanks. If my HRS S1 can accomodate the longer belt, the shorter one, IMHO, should be no problem. Have asked the dealer in Singapore for it. As and when it arrives will make the sonic comparisions in house and post results.
Cheers
Sunnyboy, your welcome. Actually you can try it now even without the belt. Just position the motor about 4mm from the plint, and you'll have the idea if it would fit or not.
I have done the upgrade from Raven AC 1, to Raven 3 to BN. I found the difference between the AC 1 to 3 motors to be very subtle. I found the upgrade to the new motor controller to be much more audible and for the better.

As far as the "science" behind the positioning of the 3 belts and 3 motors - you can follow it as such:

One motor pulls the belt that the other motor pushes. You are eliminating the slack from the belt of a single motor design. Synchronization issues aside this is the same concept used by people using 2 motors or extra pulleys etc.

TW did experiment with different motor positions and the 3 motor setup in the photos is one of many different possibilities. You do get less rolling resistance as such. Imagine the tire of a car being inflated to a higher PSI and you get better mileage. But... you do lose the friction that is needed to start up the platter and do have some slipping in this configuration.

Now on to the BN. The Motor is an improvement. Easy to compare. Just run the belt around one pully vs. all 3. The increase in Torque must account for most of it. But it was easily audible. The improvement / difference between the new battery PS vs the older PS. Very very slight (I had a hard time telling any difference).

But the difference between the BN & Raven AC as a system is significant. I personally like the look of the AC more, but the BN is just a step up. More extended highs, more defined bass without becoming lean. That is the easiest way to describe it. I did keep the same tonearms, cartridges during the change.

But as all things audio..........much of what we find sounds better has little sense at times.

That takes me back to my favorite story of my Material Science professor at Berkeley. His specialty was electrical properties or materials. He was a fairly big guy in his field and often called in to analyze catastrophes due to electrical failures etc.

So.... I go up to him and ask him what he thinks would make a difference between different speaker cables etc. His answer was simple, (in a Southern Drawl) " Ah heck, I don't know. I have those MIT cables and they just sound better."

Thanks Dgad, interesting post. Are the motors with the BN the same as the AC 1/3? I thought from pics they looked shorter/smaller and if so might have less torque. What I am wondering is; if the AC 1 motor is stout enough the addition of more doesn't add much. Where as if the BN may have been designed to use 3 smaller motors and thus the test with one compromises the set up.

I also wonder what parts of the BN give the most improvement over the ACs. Very different materials are used for platter and plinth. I also wonder if a BN platter on an AC would be the value upgrade if it can be done.

Thanks, Terry
Thanks Dgad, interesting post. Are the motors with the BN the same as the AC 1/3? I thought from pics they looked shorter/smaller and if so might have less torque. What I am wondering is; if the AC 1 motor is stout enough the addition of more doesn't add much. Where as if the BN may have been designed to use 3 smaller motors and thus the test with one compromises the set up.

I also wonder what parts of the BN give the most improvement over the ACs. Very different materials are used for platter and plinth. I also wonder if a BN platter on an AC would be the value upgrade if it can be done.

Thanks, Terry
Terry

They are all the same motors just a different external casing. Power supplies are different between the tables.

Paul