Active versus Passive Isolation Platforms for turntables

[Stacore]

Dear Ron,

Thanks for questions,

1) What would be examples of stacking similar stiffness suspensions?

Does this mean not placing a component with rubber feet on a table top which itself has rubber feet on which it sits on a rack?

Does it mean not using several mechanical "diode" grounding components in a vertical system? (For example, a table top on cones (Tiptoes) where the points face down to mechanically connect the corners of the table top to the top of the legs of a rack, and where the rack itself is on spikes to "ground" the whole system to a concrete slab?)

Technically I mean suspensions which have very close resonant points as then we risk they will to excite each other.
Practically this means if two suspensions "feel" equally stiff, stacking them can lead to random results. Yes, rubber on rubber
would be sth I would avoid.

"Mechanical diode" - please lets forget about this audio marketing concept and not comeback to it

2) Do you believe vibration control techniques should be mixed, meaning, for example, having a heavy, solid rack the feet of which are spikes, but then having Sorbothane or some other vibration-absorbing material between the top of the rack and the table top which sits on the top of the rack?

Yes, yes, yes, AND YES! NO WAY one can achieve a high bandwith decoupling/damping with just a single technique! Its impossible by the laws of physics. For example, to efficiently decouple ultra low freq. (subsonic) one needs some sort of a soft spring, something that can move. But as the frequency of the vi ration grows this spring will not be able to move so fast and will start passing vibrations through its body (skin modes). So you need another technique to overtake the job where the spring starts to be more and more transparent. Please remember about that when you see some butcher-type of a block or ceramic balls claiming audio vibration control

Your example is something I would do myself, but spikes are not vibration decoupling nor damping. They decouple in some directions and couple in other with a random effect when comes to vibration control. They are great for leveling though and this is how they were invented before audio My own mastodont rack is on spikes (on the pic I posted somewhere you'll see wide feet as at that time I was experimenting with them) then followed by pneumatic suspension.

3) The active isolation Herzan claims to work up to 1,000 Hz. Herzan suggests using a visco-elastic layer below the active isolation platform to handle vibrations above 1,000 Hz. (This remains extremely puzzling to me because I always thought there should never be any squishy rubber-type material below the active isolation platform.)

I'd rather put it on top to damp eventual resonances in the platform itself. And I can only say go by ear: try different materials critically listening each time to find an appropriate one. BTW, 1kHz active is a simply great achievement from a purely technical point of view so bravo to Herzan/Table Stable! From the audio point of view, this is where we start entering the region of the highest ear sensitivity (see Fletcher-Munson curves).

4) I am still not clear on why your product is better for audio components than an active isolation platform like Herzan.

Thank you for bringing this point! Nowhere I said that. We haven't compared yet our platform to active one so I cannot claim anything.
I said that unlike lab platforms, ours are from the beginning designed for audio and we take care of the behavior in the full audio spectrum
with critical listening at each single step. We actually see ourselves as cheaper alternatives for active platforms (we are priced slightly above
passive labs platforms but definitely below active ones), offering high bandwith, 6 DOF control achieved with different techniques.

5) What do you think of sophisticated rack and shelf systems such as Critical Mass Systems or Harmonic Resolution Systems whose products utilize, among other techniques, constrained damping layer shelves to reduce vibration by coverting vibrations into heat?

Again a very big YES to constrained layer damping (CLD)!! This is a very well known, widely used engineering technique and I would not anchor it to any commercial company, no matter what their marketing specialists say BTW, we rely for certain tasks on CLD too. But CLD is an art: you have to find the right mix of the viscoelastic plus constraining layer for a given application.

 

[spiritofmusic]

Jarek, some great input there
Prepare for some sleepless nights as Ron puts his follow up qs to you
He's on a mission to really investigate isolation, and your input is invaluable to him, and the rest of us, in making some pretty critical decisions

 

[Stacore]

Guys, its all a pleasure for me but the weekend is over and I might not have as much time as I would like to.
But please keep asking, I'll do my best.

 

[spiritofmusic]

Oh Jarek, just post when you can
We've all got time

 

[Stacore]

However, I have read claims that the top plate of the Herzan does detect vibrations coming down from the component sitting above it and attempts to correct for that. I have not read explanations from owners or the manufacturer about how this is achieved, though I have asked.

(Herzan I'm doing your job here - I expect a good beer )

This is easy - they sense the top plate obviously and try to keep it motionless. Now imagine something moving sitting on top of it (vibrations are a type of movement).
Lets say it moves to the left, lowering the left side of the top plate (think slow motion, its easier). The sensors detect this movement and the microcontroller sends a signal to correct that left-side tilt. The left side rises, bringing the top plate to the level. Voila! Passive platform would not correct the same way of course, relying on spring effect (restoring force) but if within its operating range, would prevent the movement from propagating past the platform - the isolation works both ways, there is nothing like a mechanical diode!

 

[PeterA]

(Herzan I'm doing your job here - I expect a good beer )

This is easy - they sense the top plate obviously and try to keep it motionless. Now imagine something moving sitting on top of it (vibrations are a type of movement).
Lets say it moves to the left, lowering the left side of the top plate (think slow motion, its easier). The sensors detect this movement and the microcontroller sends a signal to correct that left-side tilt. The left side rises, bringing the top plate to the level. Voila! Passive platform would not correct the same way of course, relying on spring effect (restoring force) but if within its operating range, would prevent the movement from propagating past the platform - the isolation works both ways, there is nothing like a mechanical diode!

Jarek, thank you for your reply. My comment was a bit unclear. I was talking about internal vibrations originating inside the turntable from say the motor or air borne vibrations hitting the platter, cartridge or tonearm. I thought the claim from proponents of active isolation was that these vibrations could be attenuated before they wreak their havoc on the sound. I just don't see how any isolation platform, active or passive, could effectively attenuate those vibrations by detecting them on their top plate and then responding in time. The vibrations leaving the motor hit the plinth before they have time to travel to the isolation device's top plate. Don't these types of vibrations need to be addressed by the design of the turntable itself: isolation for belt drive and suspension, energy drainage paths, absorption through mass, size/shape, etc?

As you wrote earlier, the isolation device is just too far away from the vibrations. The device will respond but long after the vibrations have already effected the movement of the stylus/cantilever and altered the sound. And there is the potential for reintroducing vibrations from the corrective action of the isolating top plate. This effect has been described to me as a kind of analog "jitter". In the case of suspended turntables, is it possible that the system (turntable plus active isolation device) create a feedback loop where one starts to rock and the other is constantly correcting that rocking motion which induces more rocking motion?

 

[Ron Resnick]

Peter, thank you for this very specific thread. You are doing a great job writing your questions on this complex and technical topic in a clear and detailed and intelligble way that both we and the industry professionals whose advice we are seeking can understand.

It is not easy to explain the exact details of our component and isolation set-ups, and even harder to discuss the theoretical variations thereon in which we are interested.

 

[Ron Resnick]

Thank you very much, Jarek.

I will drop that "mechanical diode" expression which I am sure came from some metal cone footer manufacturer advertisement.

1) Assume a floor is wood over concrete slab. Do you not believe in spikes on the bottom of racks for such a scenario? I think we always thought the idea is to allow the spikes to drain vibration down from the component above to the floor below. Is this not how spikes works?

Is the theory behind spikes to prevent floor-borne vibrations from traveling up and into the rack, so the tiny contact area of the spikes prevents vibration from traveling into and up the rack from the floor?

Should racks on concrete floors use flat metal footers instead of spikes?

Or, more complicatedly, should a set-up with no active or passive isolation device rest on spikes, but a system with a passive or active isolation device under the component at the top of the rack is agnostic as to the type of feet of the rack because such device will cancel vibrations coming up from the floor with either type of footer?

 

[spiritofmusic]

Ron, in some ways this is the last big step for me
I think we've discovered a few things
Tts esp are more challenging to get right, more so than lab gear
W all those spinning platters, motor noise, moving arms, tracking carts, undulating lps, and air full of vibns and noise (OneDirection anyone?), there is a Hell of a lot more to contend with isolating a tt than a "simple" scanning microscope in a quiet inert environment to begin
Let's all agree no number of Herzans are going to ameliorate the vibns created by the moving parts of a tt, not even going to act as a drain away from them
I have the additional complication of a rim drive that puts even more vibns into the equation
We should reasonably conclude active or passive isolation is there just to stop floor- and air-borne vibns reaching the stylus
To this end, passive or active are both applicable
Now it seems that there may be consensus that active isoln not best served by tt on a springy suspended wooden floor, due to hunt/seek effect w active platform servos
Mike Lavigne intimates in the wrong scenario the servos may so overwk they may burn out
It's no surprise that all the typical lab environments that Herzan are used in are microscopes etc on solid concrete flrs
And then there is the argument of passive v active for tts in particular, and the advantage of constrained layer tech
The chief designer of Speirs Robertson SR, a company never discussed here except by me, but take it from me up there w Herzan and Accurion, is adamant the unique moving parts demands of a tt lends itself to benefitting most from passive not active
Whenever they install isolation for gear in labs, if the piece in question has continued movement, passive is their recommendation, when it's inert and non moving, active is the recommendation
When I said he would sell me a £2k passive platform not a £6k active one, he said good, it was the correct choice, and they would be stealing from me to sell me the £6k active
True story
And now we see combining active or passive w constrained layer materials is a no brainer, from Herzan now recommending use of active w elastomers, to PeterA's hybrid Vibraplane/steel top plate/ballast hybrid, to DCTOM Dave's hybrid slate/granite/springs, to New Kid On The Block: Stacore Pl
Advanced all in one turnkey pneumatics/springs/slate/ball bearings/slate/constrained layer approach

The conclusion I'm drawing in my case is that w a springy floor and advice to go passive only, the advantages others have had w constrained layer tech and benefits of springs and pneumatics, the Stacore Advanced seems to be a blend of a lot of things that could really work, at a price midway btwn the best Speirs passive and Speirs active

 

[Ron Resnick]

I think you are accepting peoples' theories and assumptions and then making up your own new theory thereon. Until you try one of these devices in your own situation it is all speculation.

I agree that with a Herzan it makes some sense that a very springy suspension could trigger Peter's "jitter loop." However it seems just as logical that such a loop could quickly die down into a very stable situation in which the Herzan calms the spring suspension, and then the spring suspension, moving less, allows the Herzan to calm down as well.

I do not think you can figure this stuff out a priori.

 

[spiritofmusic]

Ron, just PMd you
I've heard £2k Speirs passive under a GP Monaco 1.5 tt in a room w vicious bass nodes throbbing away and it didn't miss a beat
I've heard £7k active Accurion i4 a while back under my tt
V good too, recollection is it wasn't as stellar as I was expecting
A chief engineer who designed Speirs active and passive ADAMANT only passives should go under tts
Peter and Dave big thumbs up for passive setup mixed composite materials and springs/pneumatics, pretty heartening
I can get a Speirs passive v active trial, but would have to buy the Stacore from Poland

 

[Ron Resnick]

What is the exact reason the Speirs guy said passive device only under turntables?

Peter I think has never tried an active for comparison.

 

[spiritofmusic]

His take
All gear w lots of moving parts in labs, and TTs obv included, behave better on passive
Inert gear w minimal movement, do better w active
This advice was unambiguous
Must be something to do w jitter loops that active may create w moving equipment
Or that self-generated movement by gear creates wave effects passive more suited at dealing with
He said this consideration trumps any technical superiority in isolating sub 1Hz w active

 

[microstrip]

(...) Note that the motor controller is also up on the Vibraplane to avoid floor borne vibrations.

Peter,

The vibration control business if filled with surprises. I admit that you put the motor controller on the Vibraplane because you found it sounds better that way. But theoretically I would not put in in the same surface as the turntable - the controller has a transformer that creates mechanical noise and I would prefer to keep it isolated from the turntable.

 

[bonzo75]

I've heard £2k Speirs passive under a GP Monaco 1.5 tt in a room w vicious bass nodes throbbing away and it didn't miss a beat

While I have heard the same Monaco at Purite Audio that plays through the built-in phono of the Illusonic multichannel processor into his Cessaro Liszt, I don't think it's possible to separate out the performance of the Speirs at all, just my take. As I told Keith, the phono can surely be improved.

 

[PeterA]

Peter,

The vibration control business if filled with surprises. I admit that you put the motor controller on the Vibraplane because you found it sounds better that way. But theoretically I would not put in in the same surface as the turntable - the controller has a transformer that creates mechanical noise and I would prefer to keep it isolated from the turntable.

Micro, that is an excellent point. I considered it a few years ago and listened to it both ways. I also considered putting the controller on it's own isolation, removed from the turntable. I'm still thinking about how to do that. Perhaps a Townshend Seismic Sink on the bottom shelf of my rack. In the case of my SME, the suspension towers work to isolate the motor and floor borne vibrations from hitting the platter, top chassis and armboard. I think the vibrations from the transformer of the controller will be blocked in the same way. I have learned also from isolating my massive SS amps on Vibraplanes, that SS gear does benefit which is why the controller is isolated. I am also considering lining the casework with mu metal because it is close to the cartridge, arm cable, and phono cable, but that is only an idea and may seem excessive.

 

[Stacore]

Don't these types of vibrations need to be addressed by the design of the turntable itself: isolation for belt drive and suspension, energy drainage paths, absorption through mass, size/shape, etc?

Amen.

As you wrote earlier, the isolation device is just too far away from the vibrations. The device will respond but long after the vibrations have already effected the movement of the stylus/cantilever and altered the sound. And there is the potential for reintroducing vibrations from the corrective action of the isolating top plate. This effect has been described to me as a kind of analog "jitter". In the case of suspended turntables, is it possible that the system (turntable plus active isolation device) create a feedback loop where one starts to rock and the other is constantly correcting that rocking motion which induces more rocking motion?

I think I saw a Herzan rep here. Why don't ask him directly? It's best to learn such things at the source.
My very rough guess would be that since the table response time (~0.001s) is some two orders of magnitude
shorter than the suspension movement timescale (~0.1s), the table should damp the movement on a fly so to say.
Lets say within one cycle....unless it overshoots while correcting so much as to considerably engage the inertia
of the table.

 

[Ron Resnick]

. . . but that is only an idea and may seem excessive.

Go for it! This hobby, as practiced by many here, is nothing if not a testament to the view that "anything worth doing is worth overdoing."

 

[Stacore]

Thank you very much, Jarek.

I will drop that "mechanical diode" expression which I am sure came from some metal cone footer manufacturer advertisement.

1) Assume a floor is wood over concrete slab. Do you not believe in spikes on the bottom of racks for such a scenario? I think we always thought the idea is to allow the spikes to drain vibration down from the component above to the floor below. Is this not how spikes works?

Is the theory behind spikes to prevent floor-borne vibrations from traveling up and into the rack, so the tiny contact area of the spikes prevents vibration from traveling into and up the rack from the floor?

I've never seen any merit in such theories. As I understand spikes: Out of 6 DOF (degree of freedom) they

1) decouple twisting and both tiltings (3 DOF)
2) do nothing to vertical bumping (1 DOF)
3) COUPLE lateral movements (2DOF)

Now go figure which type of the movement your rack and equipment like and which do not.

Should racks on concrete floors use flat metal footers instead of spikes?

Very good question I was trying to answer myself once. My guess was footers on concrete, spikes on suspended,
but I did not do any serious tests as I went with a pneumatic suspension, which gave me a peace of mind.

Or, more complicatedly, should a set-up with no active or passive isolation device rest on spikes, but a system with a passive or active isolation device under the component at the top of the rack is agnostic as to the type of feet of the rack because sucb device will cancel vibrations coming up from the floor with either type of footer?

I cannot confirm nor deny the first statement, but I definitely agree with the second: a properly designed suspension should be agnostic (what a beautiful expression!) to the rack-floor interface type. You invest in a platform not to have any headaches like shall I cone or should I spike. This assuming of course the rack is just plain stable in itself in the same sense a kitchen chair is stable (apparently not that common with audiophile racks )

 

[spiritofmusic]

Ked, I believe I heard the GP on the Speirs well before the Illusonic came on board
In those days, his room was a veritable swamp of nasty nodes, but the tt held firm
I believe he told me that w'out the Spiers passive he could not get the tt to behave
That's as good an advert for the Spiers passive as I need short of demoing it here
He had commented on springy suspended flrs in his Victorian house, as well as (un)sympathetic vibns from traffic outside, and the Speirs/GP was plonked on a non inert, non audiophile chest
Again, all excellent adverts for the Speirs

I return to the point, and now I think about it I seem to recall, that the Speirs designer touted passive over active in all cases for tts because despite active isolating lower down than passive, sub 2Hz and somewhat sub 1Hz, passive is more reactive ie more instantly start/stop, primarily because it doesn't react to tt-borne vibns and noise ie moving platters and arms etc
So, passive not so impressive at low frequencies but a better "fit" to the device ie tt being isolated
The GP Monaco on the Speirs passive at Purite Keith's really did sail thru his Cessaro Liszt/brutal room nodes torture test

The other cogent point the Speirs designer made was that if his passive was 97% good down to 2Hz, and 50% below 1Hz, and the active 99% good down to 2 and 97% below 1Hz (I've made these figures up just to make my point), he really feels this should have no real world bearing on our enjoyment of Lp listening
1Hz equates to a subway train several miles below the surface, travelling away from your listening room several miles away
Really, is that noise going to impinge on our listening pleasure? He certainly didn't think so
In fact these specs have been driven not by the isolation gear designers, but by the lab people who really require isolation to go to limits maybe not really needed
I have concluded that I'm not going to get obsessive about worrying if "95% below 1Hz is practically better than 50% below 1Hz", go w the Speirs advice that passive suited better to tts, pocket the extra cash, and base my decision to buy on whether a trial of Speirs passive in my room replicates the clear benefits I heard at Keiths or go for passive "plus" w the Stacore Advanced and its touted extra benefits of greater broadband isolation, and constrained layer construction that may replicate PeterA's long discussed benefits on his SME 30/12