Thanks, That FEMM simulation is really interesting, I have centered the copperplate to the outer Halbach stacks (using little aluminum spacers below these) but been not completely aligned does not seem to matter
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Purifi is making efforts to reduce hysteresis. Electro magnets wound by copper is the only iron free magnets I can think of. There are filed magnets speakers. The only location where saturation matters is in the gap here the voice coli travels and if that can be achieved it's really a big advantage. The combo of no iron and saturated gap is holy grail but at the same time most impossible.
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I don't understand your answer, it's not my area of expertise. The gap must be saturated? If that's the case, what advantages does a magnet have over iron?
OK, iron is often used as a return circuit for the magnetic motor - iron make N and S meet and thus it's a way to increase the field strength in the gap where the voice coil travels. When the field that the voice coil travels is saturated, i..e > 2,3T or there about, distortion disappears.
The B motor will create a much higher magnetic flux in the gap than A. But the gray iron will create hysteresis distortion.
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The B motor will create a much higher magnetic flux in the gap than A. But the gray iron will create hysteresis distortion.
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It should be noted that normal magnets also contain iron so just using magnets doesn't necessarily get rid of all hysteresis distortion. Only a strict copper based field magnet would be avoid of this.
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As far as I understand distortion derived from magnetic hysteriesis is caused by the signal dependent magnetic field of the voice coil (VC) interacting with its magnetic surrounding. Ideally the magnetic field around the VC should be stable and not modulated by the VC but iron structure would react to the magnetic field of the permanent magnets and equally by the magnetic filed of the VC. Coercivity is a measurement of a magnet to resist the influence of another magnet and NdFeB magnets have the highest coercivity and therefore are the influenced by the VC the least presenting a stable magnetic field to the VC
One thing which is not clear to me how much more distant iron joke would be contributing to hysteresis distortion. In my experience having soft iron directly at the magnetic gap causes significant distortion.
One thing which is not clear to me how much more distant iron joke would be contributing to hysteresis distortion. In my experience having soft iron directly at the magnetic gap causes significant distortion.
Here are frequency response and distortion figures of the 3 magnet systems I showed before(#5). I tried to label my original post but that is only possible within the first1/2 hr of posting.
A is first one with iron center and sides (VC width 12mm)
B is with 4 Halbach arrays (spaced close to have a VC width of 16mm identical to C to reduce variants)
C is with 2 outer Halbach arrays and centered inverted magnet stack with Cu spacer
A orange, b green and C violet. The frequency response is not very different up to 8k
here are the distortion graphs:
A
B
C
I expected C or B to be much better than A as they are complexity iron free (iron in a NdFeB magnet does not behave as iron by itself)
One difference is the width of the voice coil/former is narrower in A than B and C. It would be possible to try a narrower center stack in the C configuration but custom magnets take a long time
A is first one with iron center and sides (VC width 12mm)
B is with 4 Halbach arrays (spaced close to have a VC width of 16mm identical to C to reduce variants)
C is with 2 outer Halbach arrays and centered inverted magnet stack with Cu spacer
A orange, b green and C violet. The frequency response is not very different up to 8k
here are the distortion graphs:
A
B
C
I expected C or B to be much better than A as they are complexity iron free (iron in a NdFeB magnet does not behave as iron by itself)
One difference is the width of the voice coil/former is narrower in A than B and C. It would be possible to try a narrower center stack in the C configuration but custom magnets take a long time
This bending-wave transducer work appeals to me as one of the most beautiful and interesting DIY projects I have encountered for years. A real delight of DIY empiric research, based on theoretical fundaments. Some neodym magnet bars, some balsa, some paper, some aluminium, some copper wire, some resin, some more cheap and readily available ingrediens. That'it for the materials, simple, and no fancy stuff. Few bucks, but much brains instead, so to say. And so, it's a brillant, living proof that even a "poor man's material bill" can finally end up into a very, very pleasant overall final result if some ingenious care happily get matched with continuity and steady researching curiosity. I bet that Monteverdi had a lot of fun during all these years of work.
Bravo, Bravo, BRAVISSIMO !!!
I am very eager to read on, and also to learn more not only about the magnet assembly iterations, but also about the evolution of the moving structures.
Bravo, Bravo, BRAVISSIMO !!!
I am very eager to read on, and also to learn more not only about the magnet assembly iterations, but also about the evolution of the moving structures.
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