Seurat - Machina Dynamica (my company) currently makes 3 isolation devices, the most complex of which is Nimbus Sub-Hertz Platform, a pneumatic (air spring) type device. The Promethean and Nirvana are mechanical spring type devices. Nimbus is a floorstanding 28" tall stand with max load of about 40 lb.
The primary objective of all 3 of these devices is to attenuate seismic vibration, which we feel is the main culprit (as opposed to airborne vibration or induced vibration) that degrades the sound. I should mention all 3 of our iso stands address airborne and induced vibration as well as sesimic.
Nimbus is a *single* air spring design that employs (25 lb) ballast located well below the air spring, as well as special lateral support (steel spring) system, both of which required to build up lateral support for the otherwise floppy airspring. The advantages of a single air spring are: it allows use of *near perfect geometry* air spring, provides extremely low spring rate for very low resonant freq. under load and avoids (unwanted) interactions among multiple bladders/air springs.
Nimbus also employs a very large auxiliary air reservoir that is fitted to the Firestone air spring. This aux air reservoir considerably reduces the effective spring rate of the air spring (thus the system resonant freq).
The use of a single air spring and the unique pendulum (unipivot) design of Nimbus allows isolation in all 6 directions of motion. Since Earth's crust (continuous) motion produces seismic waves ("shaking out a carpet" analogy), isolation of the audio component in the 3 rotational directions, in additional to vertical direction and all horizontal directions, is quite important, relatively speaking. The (extremely strong) sesimic waves force the building to move up and down and back and forth, as well as force it to rotate. The waves are coming from many directions, so the actual dynamics of the situation is *very* complex.
Sesimic vibration has most of its energy around 0 - 3 Hz. Since the peak seismic energy is extremely low in frequency, resonant freq of the isolating device must be extremely low -- the lower the better.
Nimbus achieves 0.5 Hz resonant freq. in 2 rotational directions, about 1 Hz in lateral plane and about 2 Hz in vertical direction, slightly higher in third rotational direction.
We use selective frequency damping of the top plate to remove the last remnants of induced or airborne vibration, and any sesimic vibration that might have made it up thru the iso system.
Our latest iso gadget, Nirvana Base, employs alternating heavy masses and special free-standing helical springs to achieve extremely low isolating system resonant freqs on the order of 1 Hz or below in nearly all directions.
Lastly, Promethean is a simplied version of Nirvana Base and is recommended where heavy loads or space limitations are indicated.
