On Tue, 12 October 1999, barry lotz wrote:

> 
> Meredith
>      I have thought of maybe taking apart a speaker magnet and replacing the
> donut with something similar to the curved magnets you mentioned. One may
> need something like 3 to form a circle and 2-3 to form the thickness. It
> seems like this magnet material may be stronger than a conventional speaker
> magnet.
> Barry

Hi Barry,

I can't visualize how it would be easy to do that
without complicated machining, and, the coil would
likely be very large in diameter...not the original
coil of the speaker, and also the center pole 
would also have to be made very large for maximum gauss.
Nothing of the original speaker assembly would be of
any use, if I understand your description.  These
magnets when stood upright need separation...the
inside curve can't touch any steel attachment of the
back polarity.  I'am guessing one would need 6 to 8
of these magnets to form a circle (with slight
separation) and special everything machining and
coil size.  I think you are thinking of a different
shape than what they are...i.e., a rectangular piece,
with a total thickness curve all over, and 1/2 the
thickness is one pole, and the other half, is the
other pole.  If they were magnetized 1/2 the length
.....then one could try as you describe. 

If you are thinking of using the original speaker
assembly, and discarding the ferrite magnet donut, and,
using flat neo's, then, one could do that. One would
need enough neo's for the desired thickness of course.
That could make a experimental approach, to check on
the old versus the neo change over gauss field of the
narrow gap.  Economically it probably wouldn't be
worth the effort, I would think.

The original idea I was thinking of, is too use 2
pieces facing each other, with or without a center
pole....i.e., a regular general "U" magnet affair.
Sounds rather easy, but, these magnets somehow have
to be mechanically held apart, otherwise they crash
together into each other and go into pieces, or,
implode might be a better description.  Still....
they could be useful for that odd diameter coil,
that doesn't fit what you/one has.  More than likely
the inside curve won't match the coil curve of the
existing coil, and you wouldn't get the "max" gauss.
Even here a steel center pole would probably be
needed for the coil for max gauss.

Matching the coil to the magnet is a real pain, on
the homebrew scene.  If one has a 3 piece old 
magnet assembly where you can move the iron on
the ends, attaching these to the inside may work
out OK...if the magnet had too big a gap to begin
with....but, that depends on the coil of course.
One would still need a lockdown on the iron pieces.  

One note on these magnets....make sure you order
say, the outside curve to be like South and the
inside to be north...and the other piece to be
the opposite, with the inside south, and the
outside north...otherwise they repell of course,
if they were both the same.  All Electronics may
or may not consider this....so use the remarks
section of the order form, if, you want these
curved neo's.

Take care,

Meredith Lamb







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