Hello,
I am Marcus, Co-Founder of Seismion. I have seen our active vibration isolators being mentioned here in this thread, so I would like to reply to some questions.
Yes, we are a new company from Hannover in Germany, we have developed in the past 4 years active vibration isolators, a similar category like Herzan, TableStable etc.
Recenty we started to sell our isolators also to audiophile customers, and thankfully we got very positive reviews (there is a thread in WBF)
Vibration isolation is an important factor for many kinds of HiFi equipment which are sensitive to mechanical disturbance (especially turntables, tube amplifiers, but actually a lot of other parts, even cables).
We have made a short video about the influence of vibration isolation for turntables:
https://www.youtube.com/watch?v=xPd7Ft-vuZY
A good measure to compare the performance of isolators is the resonance frequency, because isolation starts only above that frequency. Our active vibration isolators have a resonance of about 1 Hz, which is way lower than other types of isolators, like the mentioned pneumatic isolators (Vibraplane etc). These devices typically start isolation around 3 Hz or even higher.
There are actually a lot of vibration sources in the low frequency range 1-5 Hz, like foot fall sound, building vibrations, so active isolators have a clear advantage here. And of course, also the isolation itself is better at any given (low) frequency compared to the passive isolators. You can find a bit more details on this, and comparison of passive and active on our website:
https://seismion.com/technology/
Speaking about passive and active: I totally agree to the reply of @thekong : all pneumatic isolators should be in fact classified as passive, and 'active' here only refers to automatic levelling (which does not contribute to vibration isolation). Active isolators like our Seismion, Herzan etc. typically have a feedback loop consisting of sensors, a control, and actuators, which makes them a totally different class.
We are looking for a close discussion with the audiophile community, since we want to offer a product that is perfectly tailored to your needs. As written above, most other active isolation products are designed for industrial applications, and might not perfectly fit, both from the function and from the design.
By the way, we are now able to serve any orders with short notice :)
Looking forward to a fruitful discussion!
Marcus