A world first? Passive v active isolation platforms test

Stacore said:

(...)
2) Our damped pneumatical suspension is fully passive - one pumps it and forgets.
It works on a similar principle as e.g. a suspension of a higher class car.
We could put auto-leveling valves and add a compressor,
but decided it is note necessary as, contrary to e.g. a lab,
need for an often relevelling + compressor might be quite a compromise in most listening spaces.

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Stacore said:

I must say that from a purely engineering point of view I admire the active idea.
However, with the present day technology I have some reservation, perhaps just intellectual,
regarding the audio applications: The upper bass/lower mid.
Sonically, this is perhaps the most important region - the sound foundation (not to be confused with the
max ear sensitivity a la Fetcher-Munson).
And this is where the active mechanisms stop working - within 100-200Hz. So as I see it,
in the sonically crucial region an active platform is working on its limits and starts to give up
(interesting thing would be to see how smooth it gives up). I feel somewhat uneasy with that.

Cheers,

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XV-1 said:

Hmmm. I wonder how I get a demo in Sydney of the Stacore?

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PeterA said:

I agree with Talko Audio about testing these devices under the turntable. Marc, will you still have both the active and passive units when your turntable is back up and running? This would seem to be the critical test.

Thank you for that informative post Talks Audio. Your comments about using a combination of passive and active isolation units is interesting. There is at least one case here where a member has a turntable which uses air bladders for suspension and this is in turn placed on a passive isolation shelf which then is placed on an active isolation platform. He reports positive results.

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microstrip said:

Can we know what is the optimum working pressure?

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Stacore said:

Microstrip, in the vast majority of cases tested so far, the lower the pressure the better, but differences are rather
small. As a rule of thumb we thus recommend to pump just enough air to lift the platform some 3mm above the ground.
I had two singular cases though (those were cheap CD players) when the equipment wanted quite high pressure
in the system tested.

Cheers,

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microstrip said:

Thanks - I was asking for a value in bar (pascal or psi, for our non metric members

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Taiko Audio said:

Audio applications is indeed the keyword here. Having elaborate experience with active isolation technology I may be able to shed some light on this. These active platforms are designed to cancel vibrations emanating from the floor and/or vibrations emanating from the appliances placed on their tops. These vibrations would typically be low in frequency. Dealing with vibrations caused by sound waves is not part of their design specifications. Most manufacturers of these devices offer soundproofing booths for acoustically noisy environments.
Going from measurements they do a remarkable job at attenuating vibrations up to ~200Hz, even when the source is sound. This is probably intentional as to deal with the 120/180Hz harmonics emanating from a typical US 110V/60Hz operated power supply transformer which they indeed cancel out to the point of being unmeasurable. I doubt a solid concrete floor would actually resonate strongly at higher frequencies but I have to admit I did not bother to test that specifically.
These devices do not "give up" but their motors do have a maximum range, suppose the vibrational strength is 65dB and the maximum correction is 55dB there will be a 10dB residual.

On to their use for audio applications.
Their top plates are usually rigid industrial grade aluminum and/or steel sandwiches, not something you'd like to place your hifi component on. These have unfavorable resonances in frequency ranges which are of no importance to their design specifications. These get exited by vibrations (sound). Hence you will see users of these platforms using additional "passive" isolation platforms to get a more likeable higher frequency resonance pattern. The culprit here is that these additional platforms cripple the vibration cancellation of the components sitting on top of them, and may actually cause oscillations at lower frequencies between the active platform and themselves. Using soft footers between device and active platform is another culprit, this will actually prohibit any correction of vibrations emanating from the component placed on top leaving you with just cancellation of floor vibrations (this all coming from actual measured performance). Active isolations platforms also have a feedback circuit which takes the vibrations of their top plates into account within their corrective action. A platform on top can interfere with this correction. The keyword here is rigid coupling to the active platform. A passive isolation platform would need to be rigidly bolted or glued on to the active platform to keep the full benefits of active isolation(and vibration cancellation). There can be no air pockets in between the platforms or you may end up with faulty corrections or, even worse, oscillations.

Also most of these devices employ switching power supplies so beware where you power them from. I will leave their own sensitivity to power quality out of this discussion

The technology is extremely useful for audio but you do need advanced knowledge to be able to utilize their full potential.

As for using individual platforms for individual devices, that is absolutely the best way to go. Every device will have it's own vibrational pattern. This will transmit to other devices sitting on the same surface. So it absolutely makes sense to buy a different platform for each of your devices. I would consider my budget and choose the solution that allows you to isolate your components from each other and be rewarded with much improved clarity!

As a P.S. Marc, you should really test your turntable separately, it's all about vibrational patterns, its in the basis of how they produce sound for starters, most of these are tuned towards producing a specific sound dealing with vibrations. An isolation platform can have a much bigger impact on their resulting sound then any other piece of equipment, what if it ends up sounding like a cd player

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Stacore said:

Taiko,

I now realized I might have sounded offensive. It was not intended by no means so I apologize if I sounded less than appropriate.
These are of course my purely intellectual considerations, which may as well be wrong.
One thing for sure: Lab platforms (active or passive) have been cut for the lab needs and audio applications are much more demanding.
Realizing this fact actually gave me the impulse to start my company.

All the best to you and good luck with your research and products,
Cheers

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Stacore said:

(...) One thing for sure: Lab platforms (active or passive) have been cut for the lab needs and audio applications are much more demanding. (...)

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microstrip said:

I would be more cautious - IMHO audio applications are just differently demanding and this explains a different approach. For example, sometimes FAM's must work in environments that are much noisier with a different spectrum than the typical listening room. And some optical interferometry experiences are much more demanding in some aspects than any audio.

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spiritofmusic said:

Hey Jarek, even we Brits where English is first language foul up regularly
I'm sure we're all on the same page
Back to the effects of the platform
I've just listened all the way thru to Genesis "Trick Of The Tail" and the magic of yr platform is to pull off the trick of suspending disbelief/feeling of hearing things anew, w a heightened sense of familiarity
There are so many moments on this album of low level detail, motifs, reverbs that are revealed, giving the listener ie me, a real frisson of excitement while at the same time maxxing the comfort feeling having heard the album so many times in the past
New and old perspectives at the same time
I can't put a value on how enjoyable this all is (maybe the figure on the invoice LOL?)

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