That Rochester stuff, single polarized through looks very good.
Pity nobody (so far) quotes Br , remanent field after magnetization, the important parameter for speaker design, but the "lifting" power per inch, but that´s something, allows for comparison.
In any case, they claim (and I believe them) that they are much stronger than "fridge door" magnetic sheet.
I´d buy the thickest strongest one already to build the prototypes.
Thinking outside the box: although they used flexible ones, I see no pressing NEED to use those, since they are glued to the (rigid) steel perforated backplate anyway, and any solid rectangular Ferrite bar, anisotropic and magnetized the proper way (through thickness perpendicular to backplate) will provide the MAXIMUM useful field.
As a semi-confirmation, the drawing above in post #12 mentions "permanent magnet bars", go figure.
I´ll check in Music Electronics Forum, whivh is "the home base" of Guitar Pickup custom builders, they often mention and use a Magnetic Field/Flux meter they use to check pickups after assembly, I bet it´s not too expensive and would help you a lot.
"Measuring RULES!!!" [tm] 🙂
Pity nobody (so far) quotes Br , remanent field after magnetization, the important parameter for speaker design, but the "lifting" power per inch, but that´s something, allows for comparison.
In any case, they claim (and I believe them) that they are much stronger than "fridge door" magnetic sheet.
I´d buy the thickest strongest one already to build the prototypes.
Thinking outside the box: although they used flexible ones, I see no pressing NEED to use those, since they are glued to the (rigid) steel perforated backplate anyway, and any solid rectangular Ferrite bar, anisotropic and magnetized the proper way (through thickness perpendicular to backplate) will provide the MAXIMUM useful field.
As a semi-confirmation, the drawing above in post #12 mentions "permanent magnet bars", go figure.
I´ll check in Music Electronics Forum, whivh is "the home base" of Guitar Pickup custom builders, they often mention and use a Magnetic Field/Flux meter they use to check pickups after assembly, I bet it´s not too expensive and would help you a lot.
"Measuring RULES!!!" [tm] 🙂
I received my Rochester magnets today. Seems pretty strong for rubber magnet material. It's magnetized correctly anyway. Its 5.2" wide with two grooves near the edges. One side is at .120" and the other is at .150" from the other edge apparently to facilitate slitting it lengthwise. We'll see how it works out.
for any one that wants i got roles of 50 meters for sale. 100 euro ex VAT ex shipping. for those that want to play around with them. i buy them bulk from a wholesale company that does not sell to private persons. and it is the rubber magnet i used in all my projects. you might need to cut them to size in width depending on the metal you want to use. i usually cut it down to 7-7.2mm when using R3T5 perf metal. my first planar used the magnets as is 8.5mm wide