Best Isolation HRS? SRA? Zoethecus? Symposium?

J- Badov - If what you said were actually true, the mass of the entite house (much more than 150 lb) would provide sufficient isolation. Furthermore, "electron microscopes," as a class, are not the end all do-all devices you suggest; in the overall scheme of things their performance is good but not great.

~ cheers

j-badov - The heavy mass used in Vibraplane is employed to lower the resonant freq. of the "mass on spring" system and has nothing whatsoever to do with inertia, as you suggested. System resonant frequency is a (strict) function of the Sq. Root of spring rate over the mass.

Thus, if vibraplane employed an even heavier mass, all things being equal, it would be an even better isolator. But not because of the reason you gave.

~ cheers

theaudiotweak: in the case of our Promethean & Nimbus, we use selective frequency damping of the top plate to remove residual vibration due to seismic type, component-induced or airborne type. We also prefer the extremely hard dh (diamond hardness) cones for lightning-fast energy transfer between component & plate/damper.

Geoff Kait, Machina Dynamica

j-badov, the equivalent performance (resonant frequency) for the VP would be obtained by simultaneously *reducing* the mass and reducing the spring rate of the thin-skin bladders.

Therefore, by inspection, mass cannot be the *key* to the design of the mass-on-spring isolating system you seem to think it is.

Also, a larger mass doesn't necessarily require more surface area as higher density of mass will solve that particular problem.

Maybe dust off the old university textbooks, eh? :-)

I would use abs. minimum no. of bladders (of correct geometry) -- that is one sure way to lower resonant frequency and improve performance...fluids in bladders could overdamp things... haven't tried it, might be worth a shot, but generally don't like fluids or sand...

J-badov - It appears you have your concepts of isolation and I have mine. Nothing wrong with that and I agree, no need for pissing contest. There are many ways to skin a cat.

I designed Nimbus platform, a 6 DOF sub 1.0 Hz device about 8 years ago. Nimbus is the world's only single air spring iso stand. For ballast for the Nimbus I use steel - as you say: inexpensive and well-suited to the task. Depleted uranium would be my next choice :-)

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.

Guidocorona - seismic vibrations are the energetic waves that travel along the surface of the Earth that are produced by movement of the Earth's crust, especially along fault lines -- not only earthquakes, but less intense, continuous motion ("microseismic" activity). These seismic waves have transverse, perpendicular and rotational components (forces) capable of travelling long distances with great rapidity.

The seismic wave acts on a building much like a wave on the ocean passing under a boat -- when the wave passes under it, it forces the boat to move up and down, also pushes the boat forward and back and rocks it to and fro.

For convenience, we often include under the heading "seismic vibration" other sources of low-frequency vibration: automobiles, trucks and buses; trains and subways; the effect if tides around coastal areas, the effect of wind on high rise buildings (sway), even low frequency vibration produced by large applicances in the building -- large fans, A/C, etc.

Guidocorona - Ya got me! I thought you were the one that couldn't spell, but it was I.... Good one!

Jadem6 - Excellent reaction! - the feeling is quite mutual, btw. You must not get out much...

Seurat - of course, one might ask why the gravitational wave experiment doesn't use a rack instead of a pendulum to isolate the interferometer... :-)