Hi,

 

I have experimented with this a bit over the years.  

The best response for me seems to be a large speaker magnet with added
center pole into the coil on one end and a stack of neo with added pole
piece opposing from the other end.  Set up is difficult because of the
repelling forces, low clearance inside the coil, and arc of swing.  Having a
U shaped outer pole did not help in the least and may hinder response as
well as complicate set up.   By the way, I take the face pole iron off of
the speaker magnet to prevent short circuit of the flux from the center pole
into the coil.  The inner diameter of the ceramic magnet portion is then
about the outer diameter of the coil.   I have not tested linearity but I
use a rather long coil with the poles about 30%  into the coil from each
end.  I suspect this gives linearity at the expense of some of the end
windings not receiving full flux.

 

Randy














Hi,

 

I have experimented with this a bit over the =
years.  

The best response for me seems to be a large speaker =
magnet
with added center pole into the coil on one end and a stack of neo with =
added pole
piece opposing from the other end.  Set up is difficult because of =
the
repelling forces, low clearance inside the coil, and arc of swing.  =
Having
a U shaped outer pole did not help in the least and may hinder response =
as well
as complicate set up.   By the way, I take the face pole iron =
off of
the speaker magnet to prevent short circuit of the flux from the center =
pole
into the coil.  The inner diameter of the ceramic magnet portion is =
then
about the outer diameter of the coil.   I have not tested =
linearity
but I use a rather long coil with the poles about 30%  into the =
coil from
each end.  I suspect this gives linearity at the expense of some of =
the
end windings not receiving full flux.

 

Randy