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.
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.