In regard to Casey's suggestion about an alternate magnet,
"this type of magnet" is not the exact magnet required for the
transducer design (all the dimensions are different), and I would 
certainly doubt if it is a bonded Neodymium rare earth magnet at 
that price. McMaster and other catalogues I have do show a wide 
selection of large ceramic ring magnets (as used in speakers) 
in the large dimensions mentioned and price range. The bonded Neo
magnets have about 4 times the specific coercivity of ceramic.

Regards,
Sean-Thomas

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