Magnets in Pickups

[Helmholtz]

Acc. to Zollner a stronger field shortens the aperture and thus somewhat increases treble.

[Antigua]

Acc. to Zollner a stronger field shortens the aperture and thus somewhat increases treble.

How would that work?

As far as increasing treble response, beyond a high enough frequency, the treble decay becomes so rapid that it only exists as a feature of the transient. I think the aperture is so narrow, even if should be as wide as an inch, that the involved frequencies manifest in the transient, or the pick attack, and are not perceived much in the overall treble response, from attack through to decay.

[Helmholtz]

How would that work?

He measured the change in aperture.
Saturation may be involved.
From the length of the aperture the (comb) filter response can be calculated. As the wave lenghts on each string are different, so are the filter responses.
Formulas and plots in Zollner's books.
Generally a narrower aperture is most audible on the bass strings.
I think that the attack response plays an important role regarding perceived brightness of musical instruments.
I notice a slight increase in brightness with PUs closer to the strings.

[Mike Sulzer]

If the field is stronger, then the distance along the string from over the center of the pole piece (zero magnetization) to where saturation happens decreases. It is this region where the magnetization is changing that is the source of the field that passes through the coil. Thus, stronger field, shorter aperture.

[Helmholtz]

Yes, that's what I figured.Thanks.