Upgrade from TW Acustic Raven AC-3 to what?

Well - Solong can provide an astonishing amount of insight into the setting up of the AC-1 and AC-2 respectively.
The AC-3 adds a 3rd motor - that is miles more expensive, but won't alter the performance.
The AC-2 already - if properly set-up... - does provide an AC with force-free horizontal bearing. This is the real advantage - not having a 2nd or 3rd motor, but eliminating a dreadful force vector in the horizontal plane. Thus considerably lessen the sound and the wear in the bearing axis.
It works with the Raven, it works with the Micro Seiki (their engineers put this in action with the inertia units HS-series back in the early 1980ies....), it works with every TT......
In the standard set-up of a Raven AC-2 the bearing most likely is not vector free - see Solongs set-up for illustration and inspiration and how it should be done.
Hey Solong - give us some nice pictures of your Raven AC-2 !
Its not a tweak - its applied basic physics.

Cheers,
D.

Dertonearm,
In the spirit of this discourse, you wrote "all great turntables able to provide those lowest 2 registers (and by doing so donating to the listener all the upper registers with increased ease and transparency as well...) will feature a platter weight of at least 30 lbs and way up. Regardless of bearing type or drive mechanism. It is a game of amplitude of energy implied versus mass."

Can you cite the math and/or physics that support this statement? I don't find it intuitively obvious that your generalization holds true for all turntable types. (But I will say that those who have heard both say that the SP10 Mk2 [8-lb platter] differs from the Mk3 [22-lb platter] mainly in the superior low bass response of the latter table, which is consistent with what you wrote.) Anyway, the Saskia would still qualify for your list on the basis of platter mass.

Dear Lewm, I am not familiar with the Saskia. There will be a mathematical term possible to give figures of the platter mass in relation to the energy level emitted by the stylus while extracting the information from the groove. This is of course depending on the compliance of the suspension of a given cartridge.

If you can do in the interim with some empirical research I have done in the early 1990ies, I can assure you that the 1st critical point is around 12-13 kg. The 2nd and last "barrier" (sonically...) falls around 35 kg. Above that you are in calm waters and can rest assured that even the most stiffest carts can no longer emit enough energy into the platter so to provoke any vibration of the platter which in return does alter the extract information.

It is a very similar effect as the one in billiard tables.
The picture is as follows:
- a machine kicks off a billiard ball on 2 tables covered with the same fabric and in the same room - both leveled perfectly.
On the table with the thicker stone platter underneath the fabric, the ball will run much longer.
The ball retains more of its rotating energy as the mass underneath is so much larger, that it does not deduct that energy - result: longer run.
That proven and common knowledge.
Same applies to turntables.
Put a given cartridge/tonearm combo on a TT with a platter of say 70+ lbs and you will notice while comparing to a TT with a 20 lbs platter less background noise, much more airy and authoritative bass and - surprise ... - a slightly louder playback level.
All these effects can be linked back to the fact that the cartridge/tonearm combination can do its work more undisturbed and do retain their energy.

Any math term explaining this relation must include compliance, stylus contact area, VTF, effective moving real mass, record net weight, platter net weight, contact area record to platter and - last not least.. - platter weight.

I am sure someone will help us with a formula....

Cheers,
D.

Hi,

One method that has been used many times with belt and string driven turntables is that of extreme platter mass. I suppose I did much the same with my idler driven turntable. It has a centerweighted platter of 12.5 kg. (26 lbs.) That is heavy for an idler type, but it also implements an external rotor motor, which of course, is placed near the rim of the platter. In effect, that adds an additional equivalent mass of around 168 kg. I say "around" because it depends on the rotational speed of the motor itself. That can vary due to the fact that the motor uses a regenerative speed controller that has many adjustments for pitch preference, and can also provide a higher speed for 45 rpm. (The design does not rely on any pulley configuration.) Anyway, there are various ways to skin the cat, and that one is the one I use.

Lewm,
Thanks for the mention!

Win
Saskia Turntables

Hi Mosin, to add inertia and by doing so increasing speed stability of the moving system is indeed a wise decision. However - this added "dynamic mass" is not "seen" by the stylus assembly as it is only a dynamic (sic) part of the moving system. The platter of your TT still remains at a static net mass of 12.5 kg (which still is pretty much for an idler drive and already in a serious league).
So for the model I have set up we do need the bare net mass of the platter.
The added inertia helps to stabilize the speed - but it does not help the platter in its fight against tracking-born vibrations. Its only the pure static mass underneath the record - i.e. the platter itself - which matters in this case.

Nevertheless its always a smart move to increase inherent speed stability by added inertia - even in an idler drive ( which once again shows indeed, that there are many ways leading to Rome - but in the very end they all merge at the Capitol (or the Via Appia.... in case you want it to be a triumphal march....).

Keep up the good work.
Enjoy the journey,
D.