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Understanding the science – why magnetic levitation for hifi isolation?
Some thoughts on why our feet work work so well, compared with other isolation systems. A bit nerdy I’m afraid!
We started experimenting with isolation for hifi many years ago. Spikes were very popular and we tried all sorts of variations, materials, angles, bases etc with some, but unremarkable success. Simply holding a component in the air seemed to do more for the sound, when lifting components between experiments, though this has many drawbacks and you soon run out of friends willing to help you. They also start complaining while you are tying to listen. At university I remembered someone talking about magnetic levitation being used to isolate scientific equipment, where external vibration had to be eliminated for critical experiments. Huge platforms would hover in the air with the experiments going on on top of them. They were held in place with an array of angled magnets, all pushing against each other. The cost and scale needed reducing, but I thought we could explore this avenue.
You may remember back in school, in a science lesson, dropping a magnet down a copper tube and racing it against a similar sized piece of metal or other materials. The magnet always takes longer to reach the other end. It generates currents in the conductive tube as it moves, with the same principles used in dynamos and electric motors. It has a damping effect in the case of the moving magnet, absorbing energy, this seemed a useful property to absorb unwanted energy in a hifi system.
Vibration reduces friction. You may have had an old washing machine once that would wander around the room on it’s spin cycle, as it’s contact with the floor was reduced. This too seemed interesting, as high frequency vibrations would reduce the friction between moving parts, a small contact area or point would not be unduly troublesome in a suspension system. The vibration actually helping to reduce friction and noise transmission.
Trying to balance one magnet on another is always difficult. There is a tiny region of stability, once you move from that point the magnets do their thing and with powerful magnets it can be hazardous to hold on to. Keeping the opposing magnets very close to that point of stability it is the key.
Spring, mass, damper systems are most effective when the unsprung weight is minimised. In a racing car, It is estimated that 1Kg of the wheels or moving suspension and brakes (the unsprung weight) is worth 6Kg off the car’s weight in performance terms. Mass also counters vibration, as it is harder to move if it is heavy. Our feet are made in two parts, the bottom part is small and light, compared with the heavy top, so it will take the vibration and the heavy top will add to the sprung weight (the hifi component) and reduce vibration in this critical part of the system.
The feet we make use brass for the body. It looks good, it has weight and it conducts electricity, to absorb energy when the magnets move. The stainless steel pin locating the two ends of the feet is quite slippery against the brass, but when high frequency vibration is present, there is very little friction there at all. There is virtually no direct contact between the two ends of the feet, so very little vibration gets through. Not only that, but with a sprung damped suspension system, noise created by the suspended unit, from it’s own moving parts is also dramatically reduced. The heavy top section of the feet also keeps the magnetic field well away from sensitive electrical signals in the hifi unit.
These are the main factors that give our solution a big advantage over spikes and why they cut out much more noise.