Problem description:

Magnetic  system   of  a   loudspeaker  including  cylindric
permanent magnet. Magnetic circuit is made of steel.


Model geometry:

     System height = 0.05m;
     Permanent magnet height = 0.03m;
     Outer radius = 0.05m;
     Permanent magnet radius = 0.025m;
     Air gap = 0.006m.


Parameters of material:

     Magnetic reluctivity of air = Mu0;
     Magnetic reluctivity of steel = 1000 Mu0;
     Magnetic reluctivity of magnet = 625 Mu0;

     Coercive force of magnet = 500000 A/m;

Problem is  axysimmetric.  Problem  domain  is   surrounded
by the sphere possessing zero Dirichlet boundary condition.
