Magnetostatic speaker

QuickField simulation example

Magnetostatic speaker consists of a set of permanent magnets and a planar diaphragm. Aluminum strips carrying current are attached to the diaphragm.

Problem Type
Plane-parallel problem of DC magnetics.

Geometry

Given
Permanent magnet coercive force H_C = 500 kA/m;
Current I = 0.1 A
Lz = 1 m

Task
Calculate force acting on a diaphragm.

Solution
In real device the AC current flows in the strip. Peak force value depends only on the current magnitude, and does not depend on frequency. This allows us to simulate DC problem instead of AC to calculate peak force value.
Due to model symmetry we can reduce simulation domain.

Results
Magnetic force acting on a strip of the diaphragm is 0.033N per 1m of strip z-length.

Reference: Wikipedia: Magnetostatic loudspeaker

• Video: Magnetostatic loudspeaker. Watch on YouTube.
  
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