I found an approach for decoupling of electronic apparatus I have never seen before.
Opposing magnets in the corners makes the apparatus "levitate"
The Levitator
I'd like to know more about different things we can do
to make our Audio-equipment lead a comfortable life without being disturbed by the surroundings
Air, magnets, rubber and MDF. Many materials are being used.
In various constructions. What do you have to say?
Opposing magnets in the corners makes the apparatus "levitate"
The Levitator
I'd like to know more about different things we can do to make our Audio-equipment lead a comfortable life without being disturbed by the surroundings
Air, magnets, rubber and MDF. Many materials are being used.
In various constructions. What do you have to say?
halojoy,
i saw these gadgets recently at the local AAA show in Frankfurt. They seemed to work fine, but the magnetic force only was used for the vertical levitation.
Horizantal positioning was done by friction elements, o-rings made from teflon or rubber or whatever..
I thot this was not completely thot-tru from the POV that if mechanical decoupling from the ground is done via magnets, one should go the whole path on and use magnets throughout to get rid of the mechanical contact completely. OTOH, a product using 20 Nd magnets can no longer be offered at this comparatively low price and still make money.
I bookmarked this idea however as the idea-in-itself is brilliant: as highly progessive springs the magnets do the mechanical insulating with probably the lowest space consumption by far, considered the low natural resonance frequency achievable. However, one should use the Levitator with the highest mass it can still carry. Put a sandsack on top if necessary. okokok, doesn't look nice.
I am intending to build such a gadget for myself using magnets only. Having no mechanical contact to the ground at all.
Our local surplus shop stocks Nd magnets at reasonable costs; i came up with a solution needing needing 8 magnets for vertical and 12 magnets for horizontal aligning to take all forces and momentums. I doubt one could do it with a smaller magnet count. I followed the hole&pin/slotted hole&pin stategy to avoid over-constraining. hole&pin enforce cartesian alignment, slotted hole&pin enforce angular alignment.
In order not to weaken the topplate (carrying potentially heavy equipment) one could mount 4 magnets on a cylinder mounted to the top plate and reaching into a hole in the bottom plate, carrying the oppposing magnets. This is the hole / pin.
The same with a fin carrying 2 magnets and a slotted hole having the opposing magnets. This is the slotted hole 7 pin.
Avoiding over-constraining is a practice i shall always follow, be it in electronics or in mechanics.
Airborne platform: still musing about how to do this properly. Air springs have the clear advantage that the air pressure can be adjusted to **just** carry the load, yielding in the lowest-possible natural resonance frequency achievable with the load's mass and thus being most effective in overcritical damping: the natural resonance frequency of the system being located way below the lower bandwidth of the operating frequency range, this being 20Hz-20kHz for a phono turntable.
i saw these gadgets recently at the local AAA show in Frankfurt. They seemed to work fine, but the magnetic force only was used for the vertical levitation.
Horizantal positioning was done by friction elements, o-rings made from teflon or rubber or whatever..
I thot this was not completely thot-tru from the POV that if mechanical decoupling from the ground is done via magnets, one should go the whole path on and use magnets throughout to get rid of the mechanical contact completely. OTOH, a product using 20 Nd magnets can no longer be offered at this comparatively low price and still make money.
I bookmarked this idea however as the idea-in-itself is brilliant: as highly progessive springs the magnets do the mechanical insulating with probably the lowest space consumption by far, considered the low natural resonance frequency achievable. However, one should use the Levitator with the highest mass it can still carry. Put a sandsack on top if necessary. okokok, doesn't look nice.
I am intending to build such a gadget for myself using magnets only. Having no mechanical contact to the ground at all.
Our local surplus shop stocks Nd magnets at reasonable costs; i came up with a solution needing needing 8 magnets for vertical and 12 magnets for horizontal aligning to take all forces and momentums. I doubt one could do it with a smaller magnet count. I followed the hole&pin/slotted hole&pin stategy to avoid over-constraining. hole&pin enforce cartesian alignment, slotted hole&pin enforce angular alignment.
In order not to weaken the topplate (carrying potentially heavy equipment) one could mount 4 magnets on a cylinder mounted to the top plate and reaching into a hole in the bottom plate, carrying the oppposing magnets. This is the hole / pin.
The same with a fin carrying 2 magnets and a slotted hole having the opposing magnets. This is the slotted hole 7 pin.
Avoiding over-constraining is a practice i shall always follow, be it in electronics or in mechanics.
Airborne platform: still musing about how to do this properly. Air springs have the clear advantage that the air pressure can be adjusted to **just** carry the load, yielding in the lowest-possible natural resonance frequency achievable with the load's mass and thus being most effective in overcritical damping: the natural resonance frequency of the system being located way below the lower bandwidth of the operating frequency range, this being 20Hz-20kHz for a phono turntable.
LEVITATION
Hi guys,
Many years ago I had tinkered with this idea as well as it seems to provide good isolation from the environment.
My dad used to have a very similar base for his electronic weighing device.
It needs such a base for weighing micrograms of chemical stuff.
As far as I can tell the Levitator still couples to the environment due do the need for horizontal alignment of the opposing fields.
I have no idea what the presence of these strong magnetic fields would do to electronic stuff but I am skeptical.
Now what this base used to align horizontally were simply opposing magnetic fields fixed to the sides of the topplate.
To reduce the influence of the magnetic fields on the topplate I think it should be possible to lower them,putting them closer to the bottomplate by using posts fixed around the topplate and placing these on the corners of the rectangle.
For the really heavy stuff one could possibly use electromagnets to lift a ferrous top- or bottomplate.
I never actually tried any of this so these are just loose thoughts to be taken at face value.
Another very effective isolator is lead (remember the "Lead Balloon?)
which has very good damping properties and low self resonance
Q= ~ 3Hz depending on alloy.
It has to be sandwiched between two hard slates (glass or wood) since it is easily dented by supporting equipment feet etc.
Cheers,
Hi guys,
Many years ago I had tinkered with this idea as well as it seems to provide good isolation from the environment.
My dad used to have a very similar base for his electronic weighing device.
It needs such a base for weighing micrograms of chemical stuff.
As far as I can tell the Levitator still couples to the environment due do the need for horizontal alignment of the opposing fields.
I have no idea what the presence of these strong magnetic fields would do to electronic stuff but I am skeptical.
Now what this base used to align horizontally were simply opposing magnetic fields fixed to the sides of the topplate.
To reduce the influence of the magnetic fields on the topplate I think it should be possible to lower them,putting them closer to the bottomplate by using posts fixed around the topplate and placing these on the corners of the rectangle.
For the really heavy stuff one could possibly use electromagnets to lift a ferrous top- or bottomplate.
I never actually tried any of this so these are just loose thoughts to be taken at face value.
Another very effective isolator is lead (remember the "Lead Balloon?)
which has very good damping properties and low self resonance
Q= ~ 3Hz depending on alloy.
It has to be sandwiched between two hard slates (glass or wood) since it is easily dented by supporting equipment feet etc.
Cheers,
Not such a brilliant idea. By getting a bit more isolation from floor-borne vibration, the tradeoff is greater susceptibility to air-borne vibration.
First things first, though- if tapping on your component (with the strereo powered up and the volume turned a bit past the loudest you ever listen) doesn't result in any sound from the speakers, it probably doesn't need any kind of fancy vibration isolation. Other than turntables and amps that have microphonic tubes, money is usually best spent elsewhere.
My one exception was a preamp I built where the high-end shielded cable (nominally PTFE insulated) was microphonic! Needless to say, I pulled out all that fancy stuff, replaced it with plain old shielded cable, and all was well- except for the bucks I spent for the high-priced spread.
First things first, though- if tapping on your component (with the strereo powered up and the volume turned a bit past the loudest you ever listen) doesn't result in any sound from the speakers, it probably doesn't need any kind of fancy vibration isolation. Other than turntables and amps that have microphonic tubes, money is usually best spent elsewhere.
My one exception was a preamp I built where the high-end shielded cable (nominally PTFE insulated) was microphonic! Needless to say, I pulled out all that fancy stuff, replaced it with plain old shielded cable, and all was well- except for the bucks I spent for the high-priced spread.
A friend of mine asked about magnetic suspension of a platform to place his turntable on. I did some internet research and came upon a web page by a physics professor which went into detail, formulas included, explaining why no combination/placement of magnets alone can suspend a platform.
I'ts reasonable to assume that if this could be done it would have been made into a commercial product long ago.
Years ago, I built a turntable isolation platform which hung from bungee cords at each corner. Regardless of where in the room I placed the platform/turntable, including on top of the woofer box, I could not induce acoustic feedback. The sprung platform had a resonant frequency of about 2Hz.
I'ts reasonable to assume that if this could be done it would have been made into a commercial product long ago.
Years ago, I built a turntable isolation platform which hung from bungee cords at each corner. Regardless of where in the room I placed the platform/turntable, including on top of the woofer box, I could not induce acoustic feedback. The sprung platform had a resonant frequency of about 2Hz.
All,
before i heap scorn on you UN (halojoy excluded), i am curious what Danny has to say to that, the guy who manufactures the Levitator.
He might have tried it out. and dumped for reason.
I have observed that he registered at diyAudio.
Bill,
as i am as stubborn as you and as i already had an idea how it could be done, i might try it, ignoring the fact it can't be done.
For the record: i prefer a rubber/air supsension. But no matter how i do it, it costs a lot of space.
BTW, your 2Hz bungee cord suspension does better than most TTs. 2Hz is very low and almost as low as needed.
------------
Greets,
Bernhard
PS:
UN= united naysayers
before i heap scorn on you UN (halojoy excluded), i am curious what Danny has to say to that, the guy who manufactures the Levitator.
He might have tried it out. and dumped for reason.
I have observed that he registered at diyAudio.
Bill,
as i am as stubborn as you and as i already had an idea how it could be done, i might try it, ignoring the fact it can't be done.
For the record: i prefer a rubber/air supsension. But no matter how i do it, it costs a lot of space.
BTW, your 2Hz bungee cord suspension does better than most TTs. 2Hz is very low and almost as low as needed.
------------
Greets,
Bernhard
PS:
UN= united naysayers
Bill Fitzpatrick said:
Bill,
An old trick that works well - i'm glad you brought it up. When i did it i used surgical tubing. Had lots of it around because we used it for strength training when i was swimming competitively.
A cheap Frugal-phile(tm) trick is to use squash or tennis balls cut in half under your kit.
dave
DECOUPLING
Hi,
If I'm not mistaken squash balls are made of sorbothane.
An elastomer with outstanding properties.
Since these don't contain air they seem the perfect candidate for this application.
One can easily make something like a Mission Isoplat just using a bit of imagination.
The component sitting on it should be of sufficient weight though,or weighted down for it to work effectively.
Some places will also sell sorbothane sheets which are very effictive for damping LS cabinet resonances as well.
See also:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=4990&highlight=SORBOTHANE
And:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=567&highlight=SORBOTHANE
Cheers,
Hi,
If I'm not mistaken squash balls are made of sorbothane.
An elastomer with outstanding properties.
Since these don't contain air they seem the perfect candidate for this application.
One can easily make something like a Mission Isoplat just using a bit of imagination.
The component sitting on it should be of sufficient weight though,or weighted down for it to work effectively.
Some places will also sell sorbothane sheets which are very effictive for damping LS cabinet resonances as well.
See also:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=4990&highlight=SORBOTHANE
And:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=567&highlight=SORBOTHANE
Cheers,
More than one year ago, the italian SAP come out with magnet isolator.Test and info here: http://www.tnt-audio.com/accessories/relaxa1_e.html
I've been experimenting with vibration damping under various pieces of equipment and the results are very worthwhile. A friend helped make some isolation platforms using small inner tubes along with other damping and it made a dramatic improvement when placed under a solid state pream and a HK Citation II power amp. The only problem is that the power amp is quite heavy (75lbs or 34kg) and the weight is not evenly distributed. The power transformer and output transformers are all in a line at the rear of the amp. When put on the inner tube isolator, the back of the amp sags noticeably with tube being compressed more in the back then the front.
I didn't like the way this looked and also worried if it was good for the inner tube, so I substituted squash balls. Squash balls are not made of sorbothane, but they are quite effective. I was able to correct for the weight imbalance by using 3 balls in the back of the amp and only 1 in the front. Under the weight of the amp, the squash balls compress nicely so there is no tendency for them to roll. A quick push of the top of the amp gives a small displacement followed by a quick return to the original height with no low frequency wobble.
I'm not sure its as good as the damped inner tube, but its much cheaper and easier to set up.
Anyone have some ideas on how to deal with nonuniform loads on isolation platforms? I guess I could put some weights on the front of the amp, but theres not really room.
---Gary
I didn't like the way this looked and also worried if it was good for the inner tube, so I substituted squash balls. Squash balls are not made of sorbothane, but they are quite effective. I was able to correct for the weight imbalance by using 3 balls in the back of the amp and only 1 in the front. Under the weight of the amp, the squash balls compress nicely so there is no tendency for them to roll. A quick push of the top of the amp gives a small displacement followed by a quick return to the original height with no low frequency wobble.
I'm not sure its as good as the damped inner tube, but its much cheaper and easier to set up.
Anyone have some ideas on how to deal with nonuniform loads on isolation platforms? I guess I could put some weights on the front of the amp, but theres not really room.
---Gary
WEIGHTDISTRIBUTION.
Hi Gary,
Short of putting your amp on a diet,here's something you can try out:
Have a Y-shaped support made out of U-shaped steel upon which you put the amp with the heavy part sitting on the two pronged part so the weight gets distributed there.
If that Y shape is longer then the amp itself you will gain even more stability.
For further isolation you can even provide for tapped inserts at the ends of the Y-shape and insert spikes there.
This can then be put on a slab of MDF wood and you can be put on the squash ball halves in a mirror to the Y legs to diperse vibration even more.
Always use an odd number of contact points/squash balls.
Obviously all materials have to be of sufficient strenght so they don't flex.
Cheers,
Hi Gary,
Short of putting your amp on a diet,here's something you can try out:
Have a Y-shaped support made out of U-shaped steel upon which you put the amp with the heavy part sitting on the two pronged part so the weight gets distributed there.
If that Y shape is longer then the amp itself you will gain even more stability.
For further isolation you can even provide for tapped inserts at the ends of the Y-shape and insert spikes there.
This can then be put on a slab of MDF wood and you can be put on the squash ball halves in a mirror to the Y legs to diperse vibration even more.
Always use an odd number of contact points/squash balls.
Obviously all materials have to be of sufficient strenght so they don't flex.
Cheers,
supermodel,
personally i feel fine if i get the natural frequency below 1 Hz.
Overcritical (is it called super-critical?) damping is based on the transfer function of an oscillator stimulated from outside. Below the oscillator's natural frequency the transfer funcion has practically unity gain. Stimulus frequency approaching the NF from below lets the gain rise and rise. If the oscillator's damping is low, gain raises high, if damping is zero, gain reaches infinity. Above the NF the gain falls and falls and falls into the abyss. The lower the oscillator's damping is, the steeper the fall of the gain, of the transfer function. Usually more than 24dB per octave, the slope can reach or exceed 48dB per octave.
If the NF is 1Hz or below with very low damping, then 8Hz (let's call that lowest permissible vertical tonearm resonance) is 3 octaves above and overcritical damping has a nice value at this frequency already. You walk around on a gooey floor beneath your TT and no tonearm is hopping from groove2groove. Not even trying. Not even messing up the soundstage. Call that paranoia, but i listened to such low-NF suspension TTs, high mass on TT and on platter. That's what i want, that is impact out of calmness sonically. 1Hz or lower, is fine, 2Hz, like Pink Triangle etc. is ok.
4Hz is no real suspension. It is a fake.
Dave,
cheap stone plates and bicycle tubes are also frugalphile (tm).
personally i feel fine if i get the natural frequency below 1 Hz.
Overcritical (is it called super-critical?) damping is based on the transfer function of an oscillator stimulated from outside. Below the oscillator's natural frequency the transfer funcion has practically unity gain. Stimulus frequency approaching the NF from below lets the gain rise and rise. If the oscillator's damping is low, gain raises high, if damping is zero, gain reaches infinity. Above the NF the gain falls and falls and falls into the abyss. The lower the oscillator's damping is, the steeper the fall of the gain, of the transfer function. Usually more than 24dB per octave, the slope can reach or exceed 48dB per octave.
If the NF is 1Hz or below with very low damping, then 8Hz (let's call that lowest permissible vertical tonearm resonance) is 3 octaves above and overcritical damping has a nice value at this frequency already. You walk around on a gooey floor beneath your TT and no tonearm is hopping from groove2groove. Not even trying. Not even messing up the soundstage. Call that paranoia, but i listened to such low-NF suspension TTs, high mass on TT and on platter. That's what i want, that is impact out of calmness sonically. 1Hz or lower, is fine, 2Hz, like Pink Triangle etc. is ok.
4Hz is no real suspension. It is a fake.
Dave,
cheap stone plates and bicycle tubes are also frugalphile (tm).
THE FOUR LEGGED SUPPORT.
Claudio,
Thx for the link.
Having heard about that particular design before,it represents the disadvantages the reporter mentions.
One aspect of unevenly distributed load can be elegantly overcome if Mr.Puppin had considered what I mentioned in the reply to Gary.
It allows for much better distribution of weight and since I still have to find an audio apparatus that represents well distributed mass it is the best sollution I can put forward right now.
As it stands these platforms represent too many flaws,especially when you consider the high asking price.
Regards,
Claudio,
Thx for the link.
Having heard about that particular design before,it represents the disadvantages the reporter mentions.
One aspect of unevenly distributed load can be elegantly overcome if Mr.Puppin had considered what I mentioned in the reply to Gary.
It allows for much better distribution of weight and since I still have to find an audio apparatus that represents well distributed mass it is the best sollution I can put forward right now.
As it stands these platforms represent too many flaws,especially when you consider the high asking price.
Regards,
Levitator
Just a few notes on the Levitator.
I assisted Gary Dodd some with the design aspects and was used as a sounding board for ideas, and I came up with the name. I do not own any part of the company and I do not produce them. I do assist Dodd Audio with marketing their products and the Levitator can be purchased from our web site. I am officially a distributor as are several retail stores and Bolder Cable Company.
Gary did build a unit the was completed supported by magnetic fields. It used some attracting magnets to maintain alignment.
There were two problems with that.
The first was that if you bumped it hard enough to get it to twist to where attracting magnets would pull towards each other it would slam shut with finger braking force. This was seen as a huge liability problem.
Secondly, the attracting magnets created a really strong magnetic field that could effect a lot of other things.
The opposing magnets cancel each others fields just like adding a bucking magnet to a woofer or tweeter for shielding. Hopefully this just answered one of those other questions.
The two pin system works great and does not lock the top plate to the bottom plate. The clearance used in the top plate allows some float in the horizontal plane as well. So it actually does dampen in more than one axis.
The other magnetically levitating platform mentioned from SAP locks the top plate rigidly at the corners and does not allow any dampening in the horizontal plane. I believe that unit is about $150. more expensive too.
The free air resonance of the top plate is in the low to middle teens so it also isolates it from direct air born vibrations that hit it directly.
How well does it work and can you hear a difference are the most asked questions.
Yes is does work and yes you can hear a difference.
Some differences are greater than others depending on the rack system used, the room, the volume level of the music typically listen to, etc.
My CD player sets on top of a Lovan Sovereign rack system. Each level is Isolated with three spiked feet.
In this system it makes a marginally noticed difference.
If I were to set my CD player on top of my big screen TV, then add a Levitator it makes a very noticeable difference.
The whole thing acts as a really low pass filter. The higher the frequency the more effective it is. The lower the frequency the less effect. With this design though even the lowest frequencies are filter very well.
Plus, it looks really cool right?
Wayne did a really nice review and comparison to another insolation unit that he posted in his forum. I don't know if I can post a reference to it or not. Some forums freak out and reprimanded me for posting links to other forums. You guys can let me know.
Just a few notes on the Levitator.
I assisted Gary Dodd some with the design aspects and was used as a sounding board for ideas, and I came up with the name. I do not own any part of the company and I do not produce them. I do assist Dodd Audio with marketing their products and the Levitator can be purchased from our web site. I am officially a distributor as are several retail stores and Bolder Cable Company.
Gary did build a unit the was completed supported by magnetic fields. It used some attracting magnets to maintain alignment.
There were two problems with that.
The first was that if you bumped it hard enough to get it to twist to where attracting magnets would pull towards each other it would slam shut with finger braking force. This was seen as a huge liability problem.
Secondly, the attracting magnets created a really strong magnetic field that could effect a lot of other things.
The opposing magnets cancel each others fields just like adding a bucking magnet to a woofer or tweeter for shielding. Hopefully this just answered one of those other questions.
The two pin system works great and does not lock the top plate to the bottom plate. The clearance used in the top plate allows some float in the horizontal plane as well. So it actually does dampen in more than one axis.
The other magnetically levitating platform mentioned from SAP locks the top plate rigidly at the corners and does not allow any dampening in the horizontal plane. I believe that unit is about $150. more expensive too.
The free air resonance of the top plate is in the low to middle teens so it also isolates it from direct air born vibrations that hit it directly.
How well does it work and can you hear a difference are the most asked questions.
Yes is does work and yes you can hear a difference.
Some differences are greater than others depending on the rack system used, the room, the volume level of the music typically listen to, etc.
My CD player sets on top of a Lovan Sovereign rack system. Each level is Isolated with three spiked feet.
In this system it makes a marginally noticed difference.
If I were to set my CD player on top of my big screen TV, then add a Levitator it makes a very noticeable difference.
The whole thing acts as a really low pass filter. The higher the frequency the more effective it is. The lower the frequency the less effect. With this design though even the lowest frequencies are filter very well.
Plus, it looks really cool right?
Wayne did a really nice review and comparison to another insolation unit that he posted in his forum. I don't know if I can post a reference to it or not. Some forums freak out and reprimanded me for posting links to other forums. You guys can let me know.
Indeed
Two magnets that are repelling each other in close proximity are simply acting as a spring. However they do not act as a normal spring. The force is inverse proportional to the square of the distance: F = k/(d^2). This means that if d goes to zero, the force goes to infinity. In practice this is not true, because of large leakage fluxes not going trough both magnets.
On the matter of damping, here is some basic mechanics. Most of you already know of course.
If we want to isolate vibrations, we have basically to do with a mass–spring system. As seen from the viewpoint of the mass to be isolated, such a system acts like a 2nd order low pass filter with a resonance frequency f [Hz] and a Q-factor Q. (Q is the inverse of damping factor b). The spring has a compliance c [m/N]. Further we have usually loss: r [Ns/m] and of course a mass m [kg].The resonance frequency fs of the system can be calculated as follows:
fs = 1 / ( 2 * pi * sqrt( m * c ) )
Below fs vibrations are transmitted and above fs they are attenuated at a rate of 12dB/oct. The time and amount the mass stays swinging depends on the Q factor:
Q = 2 * pi * fs * m / r
or
Q = (sqrt( m / c )) / r
So if you want to go for a pretty low fs of 1 Hz or 2 Hz, you will need a fairly high mass and a fairly high compliance. The loss also does matter a lot. A Q-factor between 0.5 and 0.7 is optimal. Below 0.5 the damping will be less effective and above 0.7 the system stays swinging too much after an excitation (a bump for instance).
A large mass will not be the problem but a large enough compliance that can hold the mass, is rather difficult. Systems with a low fs are available at industrial level. But beware, they are bulky and usually use active pneumatic or magnetic control systems.
The idea of using an inner tyre, of a small trailer for instance, for the spring is not such a bad idea. The butyl rubber they are made of has a high loss factor r also.
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