i didn't really want to start a new topic, as this thread seems like a pretty decent start to an ultimate wah inductor + magnetism compendium. i just wanted to share my experience with this subject, as it pertains to a breadboarded wah circuit (i pretty much stuck with r.g. keen's tech of wah circuit, switched the input resistor and cap order, for no good reason).
i have three inductors out-of-circuit to play with: a newfangled dunlop yellow "fasel", a plain black cylinder inductor from a standard cgb-95, and a "halo" style from small-bear (eleca is the brand).
i gathered up magnets from various sources, from really weak 16th inch by quarter inch ceramic discs that can barely hold their own weight to a couple one-inch diameter neodymium discs.
the one i settled on is probably a half-inch in diameter, maybe at most 8th inch thick, probably rare-earth magnet from a broken drive motor for a conveyor system node.
here is what i noticed: i really have to play with it to find a sweet spot. if i just willy-nilly stick it, chances are, the inductor will turn into a useless short and the wah pedal will not wah, or it will change nothing about the inductor, and will sound just like it did before it was placed.
not only do i move it around the whole surface of the inductor to find a sweet spot, but i also change the orientation of the magnet.
i have the yellow fasel on the breadboard at the moment (makes the most drastic differences), with the magnet on its spine (not sure if positive or negative), in the middle of the white plastic plate of the inductor.
i changed out a few values (im guessing that if the magnet lowers the inductance, lower inductances mean a more trebly sweep), put in a bigger sweep cap, and i like a lower value on the "q" resistor (parallel to the inductor) as people call it. everything else seems to be stock, i think i messed with the 22k (at the 9v+ to collector of q1 position) value, lowered it i think (all of the resistors are wired as rheostats atm, one leg out of circuit), and the 1k5 "midrange" resistor i tuned till i liked the midrange, havent measured yet.
some positions of the magnet make EXTREME changes to the sweep. before the point where the magnet is making too strong of an effect (i think it pushes the sweep out of audible range, personally) the sweep is VERY trebly. it is completely unusable except for the higher harmonics. sounds more like a chipmunk going "wee wee wee", instead of a wah pedal wah-ing. i tend to like the "ee" sound at the toe part of the range, so i play with it JUST until the point where it shows, and fiddle with the rest until the midrange and bass are balanced with it.
dang, i really want all the sounds, actually. lower sweeps (stacking two series inductors, or raising the value of the sweep cap) are great for muted "waka waka" things, and filtering crunchy tones.
anyway, the halo style inductor sounds better stock than with the magnet, which makes very little difference, even in the position where it DOES finally make a difference. maybe it is the metal brackets, which also make it a pain to work with the magnets.
i really want to make a video to demonstrate these experiments.
hope this thread necromancy will be tolerated!