Why do the various grades of alnico sound different?

[Possum]

...

Thats where ALL the PAF replicators FAIL. "Hey, lets make it better." Translation: "We can't effing figure out how to get that sound so lets just say we made it "better." If you're copying something the fatal mistake is to make improvements. I have Larry's original PAF attempt and its way off. Here's an amusing video:
YouTube - Guitar World reveiws the new DiMarzio PAF 36th Anniversary

[Mike Sulzer]

...the author claims magnet material doesn't effect tone whatsoever, and that if you had two magnets of the same "strength" in a speaker, they'd sound the same.

Different kinds of magnets of the same initial strength are affected to different degrees by large currents. So that statement is certainly not true for speakers, where we have currents in the coice coil large enough to affect the magnets.

In pickups, we do not have that problem.

[flyneye]

Not to add to any confusion, that video above got me to thinking when he announced he was using "9 gauge" strings on both guitars and my instant thought was "why in the world does anyone use 9s on anything that doesn't have a floyd?" Then I got to thinking, if as you change magnetic power up does taking the gauge of the strings up or down bring you closer to the goal? If the magnetic field is increased should not the mass of the string be decreased? Or perhaps if the magnet were left alone would changing up to heavier strings bring the sound to fruition? I may be biased as I generally use 11s and only occasionally heavy 10s and a baritone guitar is by far my favorite axe for it's full rich pianoesque tone.

[Possum]

....

I would think it would be the other way around, for skinny strings use hotter magnets to compensate for there not being much mass in the strings. I used to play 9 gauge strings because I had alot of problems with finger joints at one time, when I was totally vegan. I really hated them too, sound like banjo strings, no sustain, plinky tones. You pretty much have to use a gain pedal with strings like that. Or stick with humbuckers which will fatten the tone up some. Jimmy Page used 8 gauge strings back when, as most of us did, so there's that, and Billy Gibbons still uses them. But now on my Gibson short scale stuff I always use 11's, they are just about perfect for that, and nickel too, usually DR's.

[Folkcafe]

If I may be allowed to revise and extend my remarks

I did a little digesting of this subject yesterday while I worked on dealing with my parents flooding basement. One thought I had was if Possum was telling me that various manufacturers have varying recipes, there is probably one of two ways he would know this. Someone told him or he had access to the chemical analysis.

With that thought, I did a little mental review of the materials I've been reading. While not related to Alnico, I did find numerous references regarding other magnet alloys where there are additions to the chemistry. This made me think of a discussion I had with a metallurgist about a particular alloy I was working with. I understood the purpose for most of the composition but a few didn't make sense to me. He explained that these additions were to reduce the solution temperature of the alloy.

I did read something related to FeCrCo magnets where moly and zirconium is added to reduce the solution temperature. A reduction of 200C in processing temperature would certainly be desirable from the manufacturers perspective. This morning I found paper on a similar topic regarding rare earth magnets. Here the discussion was more in depth but the general idea is things like the addition of elements like Cr for corrosion resistance.

I have not found any technical references regarding Alnico chemistry variations but if there are such additions, then I would certainly conceded that it could certainly be a factor.

As perspective often clouds perception, it is easy to see that my background in producing tightly controlled alloys would make this an observation that I would initially miss. As my purpose is curiosity and I do not currently have the resources to "know" the chemistry, the point is indeed moot.

I'm beginning to suspect that Possum is more than just his forum handle.