Functionally the same as a progressive spring. Within the tiny range of motion playing music it is probably pretty linear and with freedom of motion in all planes should be about as good as any other spring. The drawback with all springs is they are resonant, and these will be too. So they will probably need to be tuned with weight just like springs. Bottom line you would have to compare but I would suspect they are maybe a little better than Nobsound springs for only about seven times the cost.
There’s already many similar products out there.
Here’s one from Triton Audio.
Apart from perhaps a minor concern of placing a magnetic field near a cartridge these devices are an intriguing alternative to springs and rubber.
Perhaps these devices don’t get the attention they should. Reviews have been few and far between but here’s one from 2009.
Russell Lichter’s Stereotimes review for
Spikesound Will Isolation Feet asks a few interesting questions which seem to have remained unanswered to this day.
"Now, I understand something of the physics of resonance, how frequencies above a resonant point meet an increasing resistance to and dissipation of vibrational energy.
For example, by installing a small bicycle inner-tube under my CD transport, which weighs 45 pounds, I created a resonant system somewhere around 3Hz, effectively isolating the transport from foot falls, earth tremors, sonic booms and the like.
It solved the occasional problem of CD skipping on playback when a non-ballerina walked through the living room.
But like any simple, under-damped resonant system, it retained kinetic energy. Not ideal.
What happens to the vibration that lies above resonance and therefore does not propagate unimpeded through a resonant system?
Some of it probably bounces back as standing waves and dissipates elsewhere. Most of it converts to heat locally.
In the case of a installation-base/compliant-element/supported-weight system, mechanical friction (typically internal friction) converts motion to heat on a molecular level.
For a relatively undamped, simple system with a single restoring force, the rate of roll-off above resonance is 6db per octave.
This means that if the resonant frequency of a system is 10Hz, a 20Hz vibration will be rolled-off (diminished) by 50%, 40Hz by 75% and so on.
ButSpike Sound Will feet do not have a mechanism for molecular friction; what flexes under external excitement is not a bicycle tube or a spring or a hemisphere of sobothane, but two repelling magnetic fields.
So what happens to vibrations that reach the base that supports the feet?"
What worries me about the Michell is that center post. It appears to fit fairly snugly, but it's hard to tell.
I can see it being extremely effective in the vertical plane. It leaves me wondering how well it does with horizontal or torsional forces.
Like others, I don't see a way to tune it other than adding mass to the plinth. And it likely works best when each foot sees the same mass, meaning that one would need to balance the mass of the plinth very carefully.
I guess it must be adjustable as most turntable designs attempt to put their centre of gravity somewhere between the arm pillar and the spindle, don’t they?
Good link, again showing just how long these things have been around.
Mark Wheeler has been investigating the relationship between good sound and unwanted resonances over at TNT for many years now - but never in a boring manner.
"Way back in the annals of this vibration control Odyssey I quoted William Blake’s idea that we cannot know how far we should go in any endeavour until we have gone too far and then return to the ideal position. The plebs chorus correctly identified when I’d gone too far and listening proved no advantage despite doubling the spend and pile of shelves."
Wha-at?" exclaim plebs, stage left,"The old scribe’s gone too far this time!"
"Indeed your old scribe has gone too far with two Space Harmonisers, four steel cones, four Yamamoto MGB-1’s and four EAR vibration absorbing feet, as the difference is a negligible plus 3 and minus 1 between this and the condition tested in the table (pun alert).
This is neither cost effective nor elegant and therefore not worth the effort."
"The Yamamoto MGB-1 are the best isolation device I have tried with the Garrard 401/SME3012 series I."
Astronomers and Long Telephoto Lens Users have used Bicycle Inner Tubes modified to be filled with Kiln Dried Sand to absorb Micro Vibrations.
A inner Tube has been Cut to produce a Length of Rubber Tube,
One End is Sealed and the Tube is filled to approx' 75% full.
The Open end is then sealed.
The Sand Filled Tube is then placed on the Telescope or Lens to control resonance that is being detected a blurring of a focus.
I have produced these myself for a friends Manual Focus 800mm Telephoto Lens and they had reported that the View Finder has a improved sharpness.
This has in the past led me to ponder a method that might ?,
improve on the effectiveness of a Inflated Support for a Device.
Using a Inner Tube:
1, inflating / deflating the inner tube to create a enlarged inner area.
2, remove the Valve from the Inner Tube, and attempt to fill the Inner Tube with Kiln Dried Sand. (A Small Funnel will be useful)
3, When filled reinstate the removed Valve and inflate the Tube.
4, Experiment with Air Inflation Pressures.
This Method allows for a Combination of Management of resonances,
Air Suspension ( Airborne Vibrations) and
Sand ( Particulate Energy Dissipation )
There are methods already in place both commercially and DIY that address the use of a Suspension/Granular Isolation.
This method I am suggesting is a Simplified Method not requiring too much beyond a already commonly used method of using a Inner Tube.
The Inflation of the Inner tube would be potentially at its best
(Vibration/Resonance Control ) ?,
if it was inflated to the pressure to allow the Applied Weight
(Sub Plinth / Device ) , to have a Air Support, with the Kiln Dried Sand being Sandwiched, in contact with the Upper Inner Tube Wall.
How Much compression applied to the Sand can be determined through experiment.
If a device is with a Uneven Weight Distribution,
Two Smaller Sized Inner Tubes could be used, to allow for the added inflation requirement for the Heavier end of the Sub Plinth and make levelling the Device easier.
There is Room to experiment with the Air Pressures used,
a cheap Pressure Gauge can be used to record the Pressure that has produced a attenuation that is perceived as offering the desirable audible presentation.
I have these in my system. They work fine. I have a set under my conditioner, one under my server and one under my pre. They don’t hurt nor can I say that they were a night and day difference. My system was very low noise to start with.
keep in mind they come in different heights and weight tolerance.
The problem with these is that there is resonance control only in the vertical direction. There is virtually no control horizontally. If you have ever tried to push to opposing magnets together by hand you will notice that they push each other away in a very slippery manner. It is hard to keep them opposed. In order to keep them opposed they have to be firmly captured and held in opposition. Springs have some horizontal resonance control but still not as effective as in the vertical direction.
MinusK platforms have almost identical control in both directions which is their claim to fame.