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

Showing 6 responses by folkfreak

Finally it's also worth noting that Frank Kuzma has also started selling these systems as well -- another convert to the cause

http://www.kuzma.si/zerovibe-6050p.html

The power cords I initially tried were the generic one that came with it, a $2k SR Atmosphere UEF L3 and a $200 basic power cord that I forget who makes. It was actually the cheaper cord that worked best, the SR cords are perhaps a bit too “warm” for this application and something more on the fast/yin side seems a better match. I’ve since moved on to a $4k Marigo platinum cord with the external PSU and this is a great fit - anyway my point is that it’s not simply a matter of spending more but of looking for the right complement so experiment and see what works for you
@mijosyyn -- re the effect it is "slap you in the face" obvious, not at all subtle. And this in the context of my TT that has a pretty effective inbuilt suspension, and was mounted on a very high end wall shelf. @bdp24 will provide an unbiased perspective ... so yes these things do have an effect. As to whether this is worth it for you I cannot answer but vibration control is in any sufficiently resolving system the prime route to continuing (increasing not diminishing returns btw) and my system employs a plethora of passive approaches as well as the one active stand described above.
The effect of the Herzan isolation on my turntable is clearly shown in the data readouts that are part of my system description. You can see the motor induced vibration that the Herzan eliminates. This is a good example of how the sources of vibration can be many fold -- both external (seismic), system generated (acoustic feedback) and system generated (motor noise in this case). You can also see the LF external vibration as well.

What is more tricky to describe is the effect of active isolation on vinyl replay. Many listeners actually initially prefer the sound with the isolation off. It can see more warm, more rose tinted, more euphonic and more pleasant. But all of this is in fact coloration. The Herzan strips all that away and actually makes my vinyl sound more like the best digital, cleaner and more distinct without that rosy glow. You quickly then begin to appreciate all of the extra details and subtleties that previously were disappearing into the goo.

I also have the external Taiko PSUs and they have a profound additional impact -- as does also adding grounding blocks to the BNC socket on the back of the Herzan, and also paying attention to the power cord driving the system.

@jbrrp1 have you at least tried a range of power cords on your Herzans? I found changes in power cord before I got the PSU to be very audible - actually the more expensive and "high end" cords didn't necessarily work best but getting the right one did make a good improvement.

Finally as @mikelavigne has noted you do need to take care what you put these active systems on. My primary stands (GPA Monaco's on Apex footers) would not be a good fit at all and my turntable now is on a rigid Adona rack (previously it was on a GPA Brooklands wall shelf with the isolation overloaded to defeat it and make it suitably rigid -- this worked fine)
@mijosytn. I already described the effect up thread, and on numerous other occasions in other similar threads and in my system description. My point was simply that it is not a subtle difference, whether you view it as a positive or not (and some listeners do not)
How about you embrace the instability and go with the Townsend seismic platforms? These really work to decouple the speaker from the floor and from seismic interference. They were ideal with my old Magic Q3s. The Magico Mpods world the same trick but via constrained layer faking on my current speakers and don’t result in wobble which can seem offputting