Why do different magnet type produce different sounds?

[Mike Sulzer]

I read somewhere (may have been Seymor Duncan blurb) that A5 had a narrow intense focussed mag field, whereas that of A2 was more diffuse and spread out; so the sensing window on the string is different, affecting the harmonic content, eg a wider window would result in more cancellation.
BS?

This effect, if it is significant, would be related to the permeability of the magnetic material in the magnetized state. Neodymium is pretty extreme in one direction: low permeability. The directions of the magnetic domains are set when the magnet is made, and external fields affect it very little. Alnico 5 and 8 have a similar property: the magnetization does have a preferred direction achieved by heating and cooling in a magnetic field aligned with the preferred direction. Alnico 2 does not, I believe. So in a pickup using rod magnets, there would be some differences in the sensing window. But is it significant compared to different inductances resulting from different permeabilities? I think the inductance change is a bigger effect, and that would make it hard to hear small differences in the sensing window.

[Antigua]

You know that you're just going to get opinions, and it really doesn't matter.

I don't know that I will only get opinion, you don't know that either. Of all the forums I've come across though, this one is by far the most technically inclined and probably has the best chance of rising above mere opinion. That being said, opinions are always welcome too.

And why doesn't it matter? Why wouldn't you want to know the "how and why" about something?

So I will say, if you read the chart it is because it has more aluminum, and more nickel, and less cobalt.

That's not a 'because'. That's like saying bread rises because there's yeast in it... what does the yeast do???

So next I ask are you jumping forum to forum on this?

I'll go anywhere I can find an answer, or even a compelling opinion if that's all there is to be had. Why wouldn't I?

[big_teee]

If you had the right equipment, it might could be measured.
Ceramics sound different, because they have no eddy currents.
Aluminum effects magnets in some peculiar ways.
A2 has a higher content of Aluminum.
Without taking some detailed measurements, it's just guesses and opinions.
It's just SWAG (Sophisticated Wild Ass Guesses).
I'm done!
Later,
T

[Tony Bones]

The same question rages amongst people interested in the other end of the signal chain where the music comes out: speakers. If you ask those guys you'll get a lot of guesses about why alnico sounds smoother than ceramic in speakers. You'll even find a few people that pretend to understand it, but really they're just guessing too. It's all guesses. Not even opinions really, but guesses.

Here's a fun fact: the people that spend a lot of time experimenting with different magnet materials in speakers sometimes agree that field coils sound better than any permanent magnet. Should we be experimenting with field coil guitar pickups? The magnetic circuit on a speaker is not entirely different from a pickup. It's just a permanent magnet with some iron to steer the flux and a comparatively huge air gap that dominates the total reluctance.

[Antigua]

I read somewhere (may have been Seymor Duncan blurb) that A5 had a narrow intense focussed mag field, whereas that of A2 was more diffuse and spread out; so the sensing window on the string is different, affecting the harmonic content, eg a wider window would result in more cancellation.
BS?

Since the magnets are physically the same size, it's hard to imagine how one would have a wider field of view than the other, but hey, that's better than nothing. Stating the obvious; AlNiCo 2 passes along less high frequency energy to the coil, as evidenced by hearing less of it come out the speaker at the end, and we've ruled out inductance since it's external to the coil and we've ruled out out magnetic strength since weak AlNiCo 5 does not equate to an AlNiCo 2 sound. The string produces high harmonics, but it's as if the AlNiCo can't deal with it with while the AlNiCo 5, can.

[Antigua]

The same question rages amongst people interested in the other end of the signal chain where the music comes out: speakers. If you ask those guys you'll get a lot of guesses about why alnico sounds smoother than ceramic in speakers. You'll even find a few people that pretend to understand it, but really they're just guessing too. It's all guesses. Not even opinions really, but guesses.

That's actually good to hear, it's nice to know that people are at least trying to tackle it, because as I said initially, guitarists settle on what is observable and don't care to ask why beyond that... there's very little actual curiosity.

Here's a fun fact: the people that spend a lot of time experimenting with different magnet materials in speakers sometimes agree that field coils sound better than any permanent magnet. Should we be experimenting with field coil guitar pickups? The magnetic circuit on a speaker is not entirely different from a pickup. It's just a permanent magnet with some iron to steer the flux and a comparatively huge air gap that dominates the total reluctance.

I'm guessing that would drain a battery pretty fast in a guitar, and guitarists don't really want to change anything anyway. I'm asking the question mostly to know, to have a factual or at least more complete understanding of how everything works together. People who are into active pickups and the like might perceive that traditional pickups are inadequate for whatever reasons, but I'm more than satisfied with the 42 AWG / AlNiCo routine.

[Tony Bones]

Since the magnets are physically the same size, it's hard to imagine how one would have a wider field of view than the other, but hey, that's better than nothing.

I tend to agree. Assuming the material is uniformly magnetized then I want to think that the external fields would have the same shape. But I could be wrong.

... we've ruled out inductance since it's external to the coil ...

It doesn't need to be inside the coils to affect inductance. It just needs to be part of the magnetic circuit which loops through the coil and around the outside back to where it started. Adding a material with high permeability anywhere in that path will raise the inductance. Not very much though if even part of the path is low u material.

[LtKojak]

I've been getting frustrated with resources around the web that promise to explain the difference between AlNiCo 2, AlNiCo 3 and AlNiCo 5. They talk about how there are different balances of alloys, that some are magnetically stronger that others, then [magic goes here] and AlNiCo 2 ends up sounding softer, AlNiCo 3 has less string pull, and AlNiCo 5 is brighter and stronger... but none of them say why. I get the feeling none of them really know why since it never gets mentioned in the ten or so webpages I've looked, at and a book I've read all about pickup design. So there's sort of a black hole of information, because if you go the magnet experts, they can't tell you why AlNiCo 2 sounds different than AlNiCo 5 since they don't care about that, they care about it's industrial applications, such as heat tolerance, shock tolerance, coercivity, the ability to change polarity, form custom shapes, etc.

So why exactly does AlNiCo 2 usually sound softer than AlNiCo 5? If it's merely because it's weaker in strength, then why doesn't a degaussed AlNiCo 5 sound like an AlNiCo 2 in a given context? IME, a daguassed AlNiCo 5 actually sounds even brighter than a fully charged one, albeit weaker, but the point being, in the opposite direction of the AlNiCo 2, which confounds the notion that the difference in sound with AlNiCo 2 owes to a weaker field.

Does anyone know what specifically causes the various AlNiCo grades to perform differently, regardless of gauss?

Side question but equally important, apparently in Strat style pickup, with the AlNiCo being in the center of the coil, the magnet material has an impact on inductance since whatever is in the center of the coil will impact how the coil performs, whether it be a magnet, air, or something else, but when you swap magnetic bars on a humbucker, there's only ever steel in the coil's core, that doesn't change. Does this mean that swapping magnets on a humbucker will have no consequence on the inductance and Q factor, where as swapping magnets in Strat pickup it would?

The answer to that question requires an in-depth knowledge of the Bohr-Van Leeuwen theorem, and ultimately deep knowledge of Quantum mechanics, just to learn what that phenomenon called magnetism is and how it works. Both are WAY over my head and I assume it'll be the same to most mere mortals.

That's why all you'll find is anecdotal references based on observation.

HTH,

[Antigua]

I tend to agree. Assuming the material is uniformly magnetized then I want to think that the external fields would have the same shape. But I could be wrong.

I'm thinking the difference in saturation / BH or remanence could change the intensity of the magnetic field, so that one would accumulate more magnetism than the other in particular locations, sort of along the same lines as a more or less evenly distributed magnetism like pdf6 said, but I haven't come across any information that suggests that's true or happening.

It doesn't need to be inside the coils to affect inductance. It just needs to be part of the magnetic circuit which loops through the coil and around the outside back to where it started. Adding a material with high permeability anywhere in that path will raise the inductance. Not very much though if even part of the path is low u material.

I'm willing to accept that AlNiCo 2 might differ from AlNiCo 5 in terms of what it does to the inductance, but the complication then is why is the difference between AlNiCo 2, AlCiCo 5 and ceramic so specific, and different from simply adding more winds or less winds to the coil? For example, taking an AlNiCo 5 pickup and adding a few more winds makes it darker, but does not make it sound anything like the same pickup with AlNiCo 2. There seems to be a physical significance over or in addition to an electrical one.

[Antigua]

The answer to that question requires an in-depth knowledge of the Bohr-Van Leeuwen theorem, and ultimately deep knowledge of Quantum mechanics, just to learn what that phenomenon called magnetism is and how it works. Both are WAY over my head and I assume it'll be the same to most mere mortals.

That's why all you'll find is anecdotal references based on observation.

HTH,

I don't know, maybe someone here has such knowledge and they just haven't stopped by to weigh in yet. I know, unlikely, but not impossible.

[Mike Sulzer]

Since the magnets are physically the same size, it's hard to imagine how one would have a wider field of view than the other, but hey, that's better than nothing. Stating the obvious; AlNiCo 2 passes along less high frequency energy to the coil, as evidenced by hearing less of it come out the speaker at the end, and we've ruled out inductance since it's external to the coil and we've ruled out out magnetic strength since weak AlNiCo 5 does not equate to an AlNiCo 2 sound. The string produces high harmonics, but it's as if the AlNiCo can't deal with it with while the AlNiCo 5, can.

The "field of view" can be influenced somewhat by the direction of the magnetization of the magnetic domains in the magnet. Some are highly aligned along the axis of the magnet; in others, domains near the outside can tilt somewhat away from the axis. I do not think this is a big effect, but it is an effect.

I do not hear large differences in high frequencies between different types of Alnico. I think this is something that would need to be checked with a double blind listening test.

[pdf64]

With regard to speaker magnets, something is way different between ceramic and alnico (I seem to remember that it's generally 5 for speakers?), eg ceramic are short and fat, whereas alnicos are longer and thinner.
At a guess, it may be something to do with the shape of the field, with the aim of optimising the filed in the voice coil gap.
So maybe different alnicos have differing field shapes?

[Antigua]

The "field of view" can be influenced somewhat by the direction of the magnetization of the magnetic domains in the magnet. Some are highly aligned along the axis of the magnet; in others, domains near the outside can tilt somewhat away from the axis. I do not think this is a big effect, but it is an effect.

I do not hear large differences in high frequencies between different types of Alnico. I think this is something that would need to be checked with a double blind listening test.

I'm curious to know, how would you personally characterize the difference between the different AlNiCo magnets in a pickup context?

[the great waldo]

Hi All

Here's some info on "Dynamic imedance"
Dynamic impedance measurements during radio-frequency heating of cornea.
Choi B1, Kim J, Welch AJ, Pearce JA.
Author information
Abstract
Hyperopia affects approximately 25% of the population. The aim of different heating modalities for the treatment of hyperopia is to steepen the central curvature of the cornea. Conductive keratoplasty (CK) involves the placement of radio-frequency (RF) lesions around a 7-mm-diameter ring concentric with the pupil of the eye. Dynamics of lesion formation during CK depend on corneal electrical impedance, which is expected to change during each 600-ms-long macropulse. The purpose of this study was to measure impedance dynamics during CK. RF lesions were made in in vitro porcine eyes at different power settings. Voltage and current measurements were acquired using a high-speed computer-based data acquisition system. Root-mean-square voltages (VRMS) and curre (IRMS) were calculated for each micropulse, and impedance was determined by calculating the quotient VRMS/IRMS. Initial corneal impedance in vitro was approximately 2000 ohms. During the macropulse, impedance decreased initially due to increased mobility of conductive ions. At higher power settings (e.g., > 70%, or maximum peak-to-peak voltage of 233 V), impedance increased after the initial decrease, indicative of local water vaporization and/or tissue coagulation. Preliminary impedance data obtained for in vivo porcine eyes were similar in magnitude to the in vitro values.

Great stuff for those people in the know.

Cheers

Andrew

[Leo_Gnardo]

I think this is something that would need to be checked with a double blind listening test.

Kee-rect! Would be a little tough to do, as the ear has a short memory, about half a minute. If a test guitar had fast swap pickups like those lucite Dan Armstrongs, and you made up a set of pickups identical except for the magnet material you could get a subjective handle on it.

It's bothering me a bit that Chuck gave you a hard time earlier today. On one hand the engineering contingent can argue "all sounds the same" with regard to capacitors, tubes & pickup magnets OTOH too many people say they hear a difference so there must be something going on we're not measuring. It reminds me a bit of the mid 60's when "all amplifiers sound the same" made its way thru the hi fi world. Of course we know they don't. Then some bright engineers came up with slew rate measurements, and that explained some but not all of the differences. Those who listen carefully, whether hi fi or guitar players can hear differences that are a big deal to them & sooner or later we come up with a way to explain it. But there's the crowd and not one in ten thousand gives a hoot whether your pickup magnets are made of ham or cheese, what's the slew rate of your power amps, or anything else, as long as the music is rockin'.

- - - - - - - -

FWIW I find ceramic mag speakers generally sound smoother than new Alnico, but that's me. Old Alnico that's lost some of its field, gets mellow, there's your vintage tone.

- - - - - - - -

I can just imagine a guitarist dragging around a couple car batteries to run field coil pickups for an hour or two of playing, with some big-ass jumper cables between them and the guitar. Unwieldy to say the least. Somebody oughta try it. Or maybe a guitar paved with solar cells for those outdoor festival concerts.