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Active isolation; what can it do for music reproduction?

i was involved in a thread about stylus drag on turntables where my use of active isolation came up. it was asked for me to discuss my views and use of this approach for system optimization. i mentioned it likely needed it's own thread to do justice to the topic. here it is.

excuse me if i get too basic here to begin with. i've not seen this subject discussed in depth on Audiogon before.

active isolation devices use piezoelectric sensors in 6 axis to sense resonance and piezoelectric actuators in 6 axis to compensate for that resonance. in essence it's a feedback loop of read and compensate. 

http://en.wikipedia.org/wiki/Piezoelectric_sensor

passive devices are more or less springs to one degree or another. springs float, settle and overshoot. active devices are relatively stiff; 500 times stiffer than passive since they can STOP and START. passive can't stop and start. you do see passive devices with automatic leveling, but otherwise they can only act passively as a spring. 

an example of an active device; the Herzan TS Series;

http://www.herzan.com/products/active-vibration-control/ts-series.html

the limitations of active devices are mainly as follows; 

---they are only really effective under 200hz.
---in stock form they typically have signal path corrupting switch mode power supplies.
---to be effective they need a solid base. which means a solid rack grounded to a solid concrete floor. suspended wood floors, or non-solid racks are going to compromise the performance.
---the gear being isolated cannot have it's own self resonance that might excite the active sensors. and not every piece of gear will benefit from active isolation. so active is very system context dependent. you can't just use it anywhere and expect a particular result.

there are very very good passive devices that approach what an active device can do; the Minus K, Stacore platforms, and Vibraplance are three popular examples. i'd recommend investigating these before considering any active devices. those examples do need the same solid floor and rack as active to be effective.

and another consideration is a passive isolation rack; the best example i can give is the Artesania decoupling rack systems. likely the best passive rack. again; a solid floor is going to allow the Artesania to perform at it's best.

finally; there is a website tutorial which can really get granular with deeper levels of information on active devices for those interested. 

http://www.herzan.com/resources/tutorials.html

lastly i will say that active devices are something you consider when you've mostly done everything else you can do and want to take things further. cross otherwise impossible thresholds of performance. you have a system that is where you want it to be. active is the bleeding edge. it will allow the music to escape the confines of resonance in a way nothing else can do. it's just physics.
mikelavigne
geoffkait's avatar
geoffkait
23,365 posts
 
Passive isolation gets a bad rap. If you take a gander at the various isolation techniques employed by LIGO the project to detect gravity waves, most of the methods of isolation are passive, and fairly traditional mass-on-spring isolation. And the challenge for LIGO was much greater than for scanning electron microscopes, inasmuch as the gravity waves have an amplitude on the order of a diameter of an atomic sub-particle.

Much of the effectiveness of isolation for AUDIO lies in the “black art” of how one implements the iso system....everything matters. How the component is mounted on the iso stand, how the iso stand is mounted, the material, shape and direction of the cones used to mount them. How many components are isolated. One common mistake is allowing cabling to exert “pulling forces” on the iso stand, degrading the isolation effectiveness. Speaking of cabling, cabling should all be isolated using fishing line or rubber bands, which are passive devices. With a little ingenuity you can accomplish as much with $1 worth of rubber bands as you can with a $17,000 iso stand.

mijostyn's avatar
mijostyn
8,570 posts
 
mikelavigna, any comments on that?
teo_audio
2,197 posts
 
Each to their own effective application, re active vs passive.

My preference is to use passive as I’ve a slowly, over the years, gained a lot of experience in implementing it, and the other half of Teo Audio, Taras Kowalcyszyn, has forgotten more about such applications than I’ve ever learned. Seriously.

Taras, for example, has been brought in as ’The cooler’, in situations that no one else has ever been able to solve or figure out (understand). He is also the only one I know of, who for a commercial or industrial acoustics install, has guaranteed hard numbers, sometimes impossible numbers.. or your money back. (FYI, no one I know of guarantees acoustics installs re hard or written down numbers, especially in the bass register area.)

And this is him being brought in by a company that was probably the original isolation experts on this planet (in the actual history of the developed trade), as they were doing it in WWII for the military.

So if someone wants world class isolation, damping or acoustics in a space or place, I’ll put Taras’ skill set and capabilities against anyone or any corporation, in a heartbeat, and with my literal head on the line. Without even blinking.

Apologies for that plug, but he never toots his own horn, ever, and thus no one knows..and they mostly get horrid installs, when his are always beyond the pale. (One of those "Oh, the stories I could tell.." things)
~~~~~~~~

Back to the subject at hand, which is that active can, many times, be re-tuned to deal with various loads, whereas passive, if it is to be tuned as best as possible, tends to have a single 'best' loading scenario or target area/zone, and then all else is a form of subtle to gross drift from that 'perfection'.  It is possible to re-tune passive systems through a load range, though, depending on how the design of the specific device is implemented.

But when nailing it, a perfectly or close to perfect passive install is preferred to active in a pro market, as passive is (loosely) considered to have higher reliability in almost any case. EG, damping a large multi billion dollar bridge or building. Active no, passive yes and no known way past that, as simple is the way to go, that is more properly failsafe. This is not always the concern in audio, so active stands a chance to get into the mix, here.
mikelavigne OP
2,237 posts
 
i would not begin to talk tech with Geoff. :-)

horses for courses.

solutions are scaled to the target situation. not sure electron microscope targeted tools (the intended scientific use for these active devices) is appropriate for the uses Geoff refers to. but.......science and industry has chosen these active units over other choices. and their tools ’work’ for our High Fidelity purposes with a few modifications.

i’ve not heard anything do what the Tana active devices do in my system.

far be it from me to suggest that maybe better choices don’t/can’t exist. i will watch for Geoff to introduce his new LIGO spec isolation hifi product line. i think that maybe when we build our rooms we do some of what Geoff refers to here. for instance; depending on the distance from major sources of ground noise we might use sand or some other material under our concrete floors. as i’m in the mountains, away from highways, surf, or train tracks, on glacial till, away from any urban center, in the middle of 5 acres, in a separate building from my house.......6 inches of concrete did the trick. does this go as far as the LIGO approach? maybe not. but those factors are passive things we do to set the stage for our other efforts.

i agree with the associated equipment comments; the link i posted above to the Herzan tutorial goes to great lengths to address that issue. ultimate resonance isolation needs a comprehensive approach.

i am planning on suspending my speaker cables from ’half rounds’ with a series of bungee cords. i have the bungee’s and am looking for the proper ’half rounds’ that will work. i want something in metal or hardwood that fits into my system vibe. even though i can quickly A/B on and off and hear the active contribution i know it will improve, as my speaker cables are heavy and i know it’s damping the reaction performance of those Tana’s beneath my amps.

and there are passive components to the Tana shelves. which i did describe above.

so i’d say i have no issue with any of what Geoff describes.
geoffkait's avatar
geoffkait
23,365 posts
 
For informational porpoises 🐬 only,

The description of the various isolation techniques used in LIGO, the Mother of all Isolation Techniques, 

https://www.ligo.caltech.edu/page/vibration-isolation

Geoff Kait
Machina Dynamica
Give me the right spring and I’ll Isolate the world 
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