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Equipment isolation and vibration damping.


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Well as has been pointed out (Barry and John?) aside from the technical issues, at the end of the day magnets are typical springs and isolate no better.

 

The Euler spring has a static force needed to start the process ... think of this as the weight of the platform and equipment. Once this static force has been reached, the Euler spring "gives" and allows further deflection easily, and this is how the isolation works.

 

Come on now, you have to admit, the levitating shelf looks cool as h*ll.

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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:) yeah but $2k

 

I did some work with magnetic levitation years ago, they do look cool, but have several problems: they are linear springs so have the same problems as other linear springs, as Barry mentioned they are unstable so have to be constrained, if you do it right you can do this pretty well, and with the short suspension distances the resonant frequencies are very high, which make it useless for seismic isolation but might be fine for much higher frequencies.

 

There IS on form of magnetic levitation that will work well, put a 1/2" thick slab of aluminum on top of some rare earth magnets spinning at 20,000RPM or so, this puts strong eddy currents in the aluminum and will provide a low enough resonance to work with seismic noise. But that high speed spinning mass might have some other problems for audio.

 

John S.

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I did some experimentation a couple days ago trying to get a low frequency suspended spring systems. It seems my original calculations were quite wrong, you CAN get a low enough frequency without much height. I tried a bunch of different springs and found out a slinky works great for this purpose, it's easy to select different numbers of coils to change the spring constant and it has a huge extension ratio.

 

The upshot is four Slinkys suspending a platform actually do a very good job of isolating in both horizontal and vertical directions. It only takes about a foot of extension to get it working well. A practical implementation could be built with a framework going up a a foot or so above the "bottom", with the platform (I prefer thick aluminum) suspended by Slinkys (juniors are thinner so probably look better, I have not done any testing to see which is better). If the platform is suspended a half inch or so above the bottom, then to push buttons etc just push the platform down into contact with the bottom, do your thing, then slowly release.

 

I hope to have something built along these lines this summer.

 

John S.

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I haven't tried it, but I foresee some issues:

 

If you affix the top plate to the entire circumference of the top end of each slinky, it will be quite stiff horizontally, so you won't get much isolation from horizontal forces.

 

Conversely, if you attach each slinky to the top plate at only one point, the entire mechanism will be free to swing horizontally like a child's swing.

 

You need some resistance to damp the springs' vertical oscillation.

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There IS one form of magnetic levitation that will work well, put a 1/2" thick slab of aluminum on top of some rare earth magnets spinning at 20,000RPM or so, this puts strong eddy currents in the aluminum and will provide a low enough resonance to work with seismic noise. But that high speed spinning mass might have some other problems for audio.

 

John S.

 

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A practical implementation could be built with a framework going up a a foot or so above the "bottom", with the platform (I prefer thick aluminum) suspended by Slinkys (juniors are thinner so probably look better, I have not done any testing to see which is better). If the platform is suspended a half inch or so above the bottom, then to push buttons etc just push the platform down into contact with the bottom, do your thing, then slowly release.

 

John S.

 

It's rather a severe penalty for impatience to watch your DAC launched across the room, though.

One never knows, do one? - Fats Waller

The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein

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It's rather a severe penalty for impatience to watch your DAC launched across the room, though.

 

I envision the room, with everything (computer, DAC, amp, speakers, etc.) suspended from slinky spring boards, and the resulting SAF. Not to mention your friends and neighbors, who are all expecting you to start wearing a colander on your head any day now :) "Oh don't mind him, he's an audiophile..."

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Just got my ball and cup isolation solution - the cup has a wall to restrain the ball.

The video below shows the balls oscillating nicely in the cup.

 

Note: This is not Barry's design but appears very similar conceptually.

 

Cup%20Design.jpg

 

 

 

 

Now to wait for my shelf design to arrive before testing it under my DAC.

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Clearly microscopic deflections will not cause the pendulum to move.

 

For the goal (isolation from seismic waves, mostly P-waves), the amplitude are tiny: people who use this already told us that.

 

So, the way I see it is: maximise the isolation by using a flat surface, and then find out how to deal with the practical aspects of it.

 

One annoying aspect of one of my solutions (I have many alternatives) is that the balls may move around on the flat surface until they reach the curved end.

 

Now, if that curved end is too near, this will happen sooner than later. Therefore, a larger bowl is interesting, so that you don't have to periodically go place the balls near the centre as often as with a smaller bowl.

 

The amplitudes are tiny, and hence the motions are tiny.

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Pretty cool, it would have been fun to test this on top of the ball and cup method - but at $2000 it's too expensive for testing (at least for me). Normally the little vertical rods that it uses to keep the levitating platform centered could be a source for vibration, but if it were sitting on a properly implemented ball and cup arrangement then any horizontal displacement would be absorbed and not transferred to the little vertical rod. This would be a good x-y-z solution if someone can figure how to DIY one for way less $$$.

 

Or below it!

 

The rods, if properly implemented can be very interesting even for supporting two flat surfaces with ball in between: we could use little springs or little Euler springs (on second thought, I don't think Euler applies here, just normal springs could do) that really kick into action if the lateral displacement starts to reach a threshold.

 

Symposium also uses magnets in its ISIS racks, but not for levitation, but rather as a friction-less way to move the balls back to a central position.

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Now of course my first thought is while good for mechanical de-coupling, what does a rather strong magnetic field in the vicinity of an electronic piece of gear do? Is it better or worse than the vibration? Though the shelf will allow small movement to decouple vibration it also necessarily will move the magnetic field an equal amount which will induce currents anew in the device on the shelf.

 

Good point.

 

I am weary of magnetic fields, and anything having to do with EMI (weary of RFI too), unless that is, you specifically need a magnetic field to solve a particular problem in audio (which I have in one of my newest designs - for different goals than this thread - which is far from implementation for now).

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https://en.wikipedia.org/wiki/Earnshaw%27s_theorem

However, servomechanisms, the use of diamagnetic materials, superconduction, or systems involving eddy currents allow stability to be achieved.

 

In some cases the lifting force is provided by magnetic levitation, but stability is provided by a mechanical support bearing little load. This is termed pseudo-levitation.

 

Exactly, rotation can stabilise arrangements, and is actually part of what makes the Levitron possible:

 

The Physics of Levitron.

 

fig2.gif

 

 

 

We receive numerous queries from LEVITRON owners asking for an explanation of how the LEVITRON works. Many express puzzlement that it works at all, often citing a theorem due to Earnshaw (1,2) as proof that it should not work.

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Come on now, you have to admit, the levitating shelf looks cool as h*ll.

 

Here's another fun audio contraption:

 

 

You wanted floatin', here's floatin' for ya.

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I did some experimentation a couple days ago trying to get a low frequency suspended spring systems. It seems my original calculations were quite wrong, you CAN get a low enough frequency without much height. I tried a bunch of different springs and found out a slinky works great for this purpose, it's easy to select different numbers of coils to change the spring constant and it has a huge extension ratio.

 

Very cool, John.

 

The upshot is four Slinkys suspending a platform actually do a very good job of isolating in both horizontal and vertical directions. It only takes about a foot of extension to get it working well. A practical implementation could be built with a framework going up a a foot or so above the "bottom", with the platform (I prefer thick aluminum) suspended by Slinkys (juniors are thinner so probably look better, I have not done any testing to see which is better). If the platform is suspended a half inch or so above the bottom, then to push buttons etc just push the platform down into contact with the bottom, do your thing, then slowly release.

 

I hope to have something built along these lines this summer.

 

Nice. The thing to look out for here is the resonant frequency of the combined Slinkys and other parts of the arrangement, right?

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Just got my ball and cup isolation solution - the cup has a wall to restrain the ball.

The video below shows the balls oscillating nicely in the cup.

 

Note: This is not Barry's design but appears very similar conceptually.

 

Cup%20Design.jpg

 

 

 

 

Now to wait for my shelf design to arrive before testing it under my DAC.

 

Looks great, Nikhil.

 

If one day you can get some of the flat shallow steel dishes, try those too.

 

What's the cup?

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I haven't tried it, but I foresee some issues:

 

If you affix the top plate to the entire circumference of the top end of each slinky, it will be quite stiff horizontally, so you won't get much isolation from horizontal forces.

 

Conversely, if you attach each slinky to the top plate at only one point, the entire mechanism will be free to swing horizontally like a child's swing.

 

You need some resistance to damp the springs' vertical oscillation.

 

This reminds me I had a question which has been popping up in my head from time to time: Townshend's pdf only illustrate P-waves and it looks like it is implicit that his spring+air+rubber also does isolation/vibration-damping in the vertical direction.

 

Is it also implicit that his solution also deals successfully with tilt as the spring+rubber comes back to equilibrium position?

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Did a few tips today from CDs, so took the opportunity to float the iMac on a cup-and-ball, using the Mac's existing aluminium base, as well as the DVD reader/writer.

 

Connected the DVD reader/writer through my AC filter box as well...

 

Only the amp remains for the stereo setup.

 

Then I'll probably extend the same to the sub, the centre channel, the Blu-Ray player, the SET Tube amp when it's repaired, etc...

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Or below it!

 

The rods, if properly implemented can be very interesting even for supporting two flat surfaces with ball in between: we could use little springs or little Euler springs (on second thought, I don't think Euler applies here, just normal springs could do) that really kick into action if the lateral displacement starts to reach a threshold.

 

Symposium also uses magnets in its ISIS racks, but not for levitation, but rather as a friction-less way to move the balls back to a central position.

 

I think you are better looking at curved cups both above and below the ball rather than a flat surface. A flat surface is just going to cause headaches to no end.

 

I suppose if you wanted an active system, you could have rods at each corner driven by the equivalent to a voice coil which received signals from a sensor to maintain active leveling and decoupling. I also remember some carmakers had fluid filled dampening pads on engine mounts. The viscosity could be varied by an electric signal sent through the fluid. Sensors allowed that to damp engine motion and vibration. None of that sounds easy as DIY project though.

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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Partsconnexion has these magnetic levitation dampers in sets of 4 for $150 for those who can afford them:

76751.jpg

 

vib_open.png

 

Supposed to be focused on vertical isolation, but deals with some horizontal displacement as well.

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Not sure the company is still active, but here's a review of the SAP Relaxa 1 levitation platform:

 

There are several ways to escape from Earnshaw's limitations: you can use a spinning system (gyroscopic effect) like the ones used on magnetic bearings, you can make the whole system "active" by means of electromagnets controlled via software and position sensors (and feedback), more or less like on MagLev Japanese trains and/or you can make use of superconductors (Meissner's effect) at temperatures near the absolute zero or near -100 C with high critical temperature superconductors.

 

relaxa1.jpg

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I think you are better looking at curved cups both above and below the ball rather than a flat surface.

 

Not if you want to maximise isolation.

 

A flat surface is just going to cause headaches to no end.

 

Not headaches, just its own set of design and practical implementation constraints.

 

I suppose if you wanted an active system, you could have rods at each corner driven by the equivalent to a voice coil which received signals from a sensor to maintain active leveling and decoupling. I also remember some carmakers had fluid filled dampening pads on engine mounts. The viscosity could be varied by an electric signal sent through the fluid. Sensors allowed that to damp engine motion and vibration. None of that sounds easy as DIY project though.

 

Could be easy to work something with Arduino, relays and motors. I had actually planned to build a whole CNC machine with those. You could do a 6-DOF active isolation platform.

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A more affordable alternative to Stillpoints. They look good:

SBD_Isoped_grouping_3_sizes_new-476x321.jpg

 

$90 each for the smallest ones.

 

He also has racks.

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I have only read seven pages; so if some of my questions have been answered, please pardon me. I intend to read them all, I would like to try Barry's design and following are my questions:

 

 

1. As I understand, we need a piece of plywood, say 16”x16”- ¾” birch is a good start, a Bicycle Tube, say 18”, plywood goes on slightly inflated tube, then we need to place what I would call a steel puck (because it looks like that) with a dimple on one of the flat surface of the puck, then a steel ball on the dimple, and then we place our component on these three puck/steel balls in an equilateral triangle arrangement. I think all other things are simple to acquire; except the steel puck, so the questions:

2. Where to find the steel pucks. If we need to get them made, then what is the depth of the dimple, and what should be the radius of the curvature (that will give the diameter of the circle on the puck) of the dimple. Alternatively, I think a flat indentation will provide least contact area between the ball and the puck and would be lot easier to fabricate, unless there is another reason. I know equipment will sort of float in flat surface, but I think cables will provide restraint (that is another question if cables are connected then how we say it is isolated, but if works, that is good for now). Anyone found a steel cup with flat recess? I found this whiskey pucks Houdini Deluxe Stainless Steel Freezable Whiskey... : Target

If I can get a recess made on one side and polish it, I think it should work, it is 2” diameter and 1” high.

3. I have found tungsten carbide balls on Amazon; http://www.amazon.com/Tungsten-Precision-Tolerance-Diameter-Sphericity/dp/B00CNM7EL6/ref=sr_1_2?ie=UTF8&qid=1436619788&sr=8-2&keywords=tungsten+carbide+balls

4. 3/8” are the largest on this site for about $6.42 each; are they big/small enough.

5. In my HQ Player setup I have an HQ Player PC, another NAA PC, DAC, pre-amp, and amp. I cannot float the speakers, too dangerous. Which is a good place to start, DAC or NAA pc?

 

Thanks.

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