Tables That Feature Bearing Friction

Dertonarm, I completely agree with you that the job of a turntable motor is only to bring the platter up to speed and then keep it from slowing down. Where I disagree is that platter mass alone is the the cure all for speed stability. A large platter mass does not negate the importance of motor quality or the quality of the drive mechanism.

In this thread there is a lot of discussion about physics. Of course what is happening in a turntable is about physics. But I posit that good turntable design cannot be purely about physics. There are several reasons that this is the case:

1) Nobody fully understands exactly what the physics are. There are a lot of very subtle things going on in a turntable that to date are not fully explained. There are plenty of theories and opinions, but not a lot of facts.

2) Good turntable design is all about producing good sound. Unless the relationship between sound and physics is fully understood then physics alone cannot be an effective method for designing a good sounding turntable. Harmonic distortion in an amplifier is physics. But building an amp with super low distortion often does not produce good sound.

3) Design is also about compromises. There are compromises to control costs that apply to any turntable design commercial or otherwise. A good designer will make the compromises that deliver the best value for the money and effort expended. In addition to cost compromises there are compromises related to balancing of conflicting technical goals. Coupling vs isolation, damping vs rigidity, light vs massive. Focusing on only one objective usually delivers poor results.

4) Like it or not good sound reproduction is a subjective pursuit. There is no such thing as an ultimate sound system nor is there or will there be an ultimate turntable. Everybody has their own set of musical priorities and no design will be a fit for everyone.

Back to platter mass I have done a lot of experimenting with various platters. I find that to my ears heavier platters do sound notably better. I also have found that a heavier platter makes that quality of the motor and drive system less critical. But even with a 70 pound platter subtle changes like belt material and even the motor pulley composition are still easily heard and are musically significant. Less subtle changes like rim or direct drive are even more obvious.

Dear Dertonarm: I agree with you on your TT approach. IMHO this is a " road " to follow but IMHO it is not the " only and best " road. There are other examples speially on DD TT designs and certainly there are other " roads " in the brain of TT designers that they are not try it yet.

I agree too with Teres that physics tell us part of the whole " history " but there are several factors that affect and change what we are hearing it does not matters if the physics is on target, of course that everything the same a TT or any audio item that achieve a scientific approach is a better one and has to perform in better way too.
IMHO I think that are many " things " that till today no one already made a in deep research to find in a scientific way the. why's, where's and how's on each single TT design.
I know this because is something that I'm learning through our self tonearm design, where I'm " discovering " things that I never imagine can/could affect to quality performance.
Well, IMHO that happen too with TT's where scientific rules/law can't give us all the answers ( relationship factors ). Of course that if someone makes the research can/could have scientific answers but maybe to find out all those answers he will need not only know-how but a lot of time,money and common sense.

I like you and almost all people that cares about top quality performane/designs hate compromises/trade-offs but unfortunately these ones exist and the best each one of us can do is try to choose the " best " overall ones: such is life!

Regards and enjoy the music.
Raul.

Yes, aramid fiber: http://scientificsonline.com/product.asp?pn=3034863&bhcd2=1232817787

Raul.

Dear Teres, dear Raul, I guess we all agree in most aspects regarding the main topics / issues of designing a turntable.

I just have a very different threshold for "compromise". However I would like to answer Teres's 4 points first and in order.
I will speak very frankly here, as I just do not want to waste time and words.

1) Well - the physical phenomenons regarding the turntable CAN and ARE fully understood. Unfortunately and apparently not by the majority of turntable designers.
This is NOT all that difficult.
Unfortunately there are a lot of ill-founded theories and nice opinions around - right, but there are also the facts.
It is a fairly simple model consisting of two parts linked in one moving mass.
We have a rotating mass (the platter), that has to been kept on constant speed. The speed vector is provided by an external source (the motor ....whatever motor) the imperfections of that source (vibrations, unconstant speed) shall not be transmitted to the moving mass. This is one part of the whole system.
The second part is the act of extracting the musical information from the record groove. This act is a long line of different (both in amplitude and frequency) mechanical impulses transmitted into the record and into the rotating platter (the moving mass in motion = part one of the whole system). These mechanical impulses (which are a direct by-product of the stylus extracting the information from the modulated groove) depend on the VTF and the compliance of the cantilever (a FR-7 with low compliance and 2.6 gr VTF will transmit much more energy into the vinyl compared to a Shure V15 mk5 or similar (to name two extremes) while running through the groove and de-modulating the engraved information).
However the moving mass - the rotating platter - is therefor "threadened" by mechnaical vibrations from 2 different sources and (maybe - if anything like direct coupled) variation in speed from its external source of speed.
How to solve problem no. 1 (source of speed = motor) was discussed by me the last 2 days and is so far the only suitable solution if you want to use a motor (or multiple which is NOT a good idea...) at all.
One major point needs to be mentioned here which was so far not brought up: - of course the bearing of ANY turntable trying to bring out anything near the best possible must be TOTALLY free of any force in horizontal direction.
In other words - free of any force vector.
In plain words - there MUST be a counterpoint creating the very same force as the belt, thread, string etc. from the exact opposite direction and thus elimination that force to total zero.
Before this is not done, we do not need to talk at all about variations in speed, stylus drag, etc.
A direct drive doesn't have that problem of course.

Due to the fact that the act of playing a record does indeed brings the record into vibrations we need a heavy platter ( thats why heavy platters - if of any quality - ALWAYS do provide more substantial sonic information in both frequency extremes).
This platter must be - seen as a body - as insensible to vibration as possible. Consequently we are leaving the shape of a flat disc and platter and strive (if possible ....) towards a "round" cubus or (theoretical ideal) ball. To further increase the insensibility to vibrations other than shape is creating a compound "platter" made of materials of very different resonance behaviour
These are basic fundamental physics and nothing special.
The higher the rotating mass, less and less energy will be transmitted ino the platter.
If teh record is clamped firmly to the platter we (in an ideal situation...for which we can strive...) see the records mass being part of the platters mass. Thus less and less information will be dulled and smeared by a vibrating record (as Kirkus will agree, this is very similar model to a woofer working in a rather light and resonant wooden cabinet compared to mounting it in a stone wall - we both know that the dynamic, detail and clarity in impulse is dramatically different in these two mountings. It should be clear why.) and the pureness of information is greatly enhenced.

The point of suspension from outside mechanical resonance (building resonance) was discussed earlier and the solution is simple and can be obtained as a lug-and-play solution from suppliers already mentioned.

2) A turntable does not provide good sound.
A turntable has to had no sound at all. As above stated - all sound and music (should...) come from the LP itself. All the turntable can do is not ruin it. A good turntable is a dead turntable (as regarding sensibility to vibration and inner resonance). There is no such thing as a "good sounding turntable" or a turntable with "emotion (aside from its outlooks...)" or with "rythmic drive".
I mean these turntables may sound "good" and give the impressions of the above mentioned sonic features.
But they only allow these positive features to unfold.
They are in the record.
The other TT's just destroy and dull them in one way or another to more or less extend.

3) Nowhere is the relation between "good sound" and pure physic as easy and as direct as in the turntable.
I will always agree that there are tastes and many different ways to reach (Rome...??) excellent sonic results in speaker design, amplifiers and cartridges (I am less generous with tonearms.....) - and yes, we do indeed NEED distortion in amplifiers (2nd harmonic order..... only.).
No so in turntables.
Its all physics here - no mystery, no genius, no secrect, no ideology.

And again - if we are talking designing a turntable as a "product" for a "market" with "value for money".
Well, - than this discussion is futile from the very beginning.
A turntable very clos eto perfection CAN and WILL be build.
But it will NEVER qualify for a commercial product.
We do not need to compromise because the turntable is so difficult to build.
We need to compromise to make it to a "product".
Because here some people must have their financial share.
The product is the compromise - the compromise is not nessecary per se.

4) A turntable does not sound.
It allows information to be extracted without alternation - or it fails in some parts or many.
Allowing some parts and smearing and dulling others results in a "sonic signature".
All other parts of the audio chain do indeed have sonic individualities - cartridges, cables, amplifiers, speakers. All these are either elctrical devices or transmitters between the mechanical and electrical world (cartridge and speakers).
Not so for tonearms and turntables.
They are purely mechanical devices.
And we can make them closer to perfection as any other part of the audio chain.
We just have to be consequent and dare.
As for the perfect turntable - in the words of your new president: .... yes we can.....

I totally agree with you that the high mass platter does make the motor / belt / thread less critical.
But if you combine a super high quality motor with excellent power-supply with a really heavy platter and superb bearing and drive counterpoint - then we getting close in bring part one of the system close to perfection.
This is very significant regarding a vibration and force free system - and thus - after all, significant for musicality.

There are some good ideas:

BUT

super high quality motor

- the Designer has to know this part
- he has to know how to use it
- he knows, it makes his product more expensive

excellent power-supply

- see above

really heavy platter

- the Designer has to know: this alone is not enough
- he has to know how to use it
- he knows, it makes his product more expensive

superb bearing

- too expensive

superb drive counterpoint

- well, you know now: expensive

What is the most hated word today?
I think: expensive
The customer would probably pay the price, but he pays it also, when a "Test review" is great (whatever this means)
or when his wife says "Great, I like it"
Most don't need more.
Or?
A real audiophile lives in pain or is Single :)