| 摘要 |
A drive assembly for a loudspeaker comprises a permanent magnet (42) and pole pieces (44a, 44b, 44c, 44d, 44e, 44f, 44g, 44h, 46a, 46b, 46c, 46d) of ferromagnetic material. The pole pieces define an air gap (43) in which a coil formed from windings (40a, 40b) on a former (41) is movable. The shaping of the pole pieces to form air-filled recesses extending to the air gap has the result that the path of the magnetic flux of the permanent magnet is split in the region of the gap and the magnetic permeability of the path of the magnetic flux of the secondary magnetic field induced in the coil upon energisation thereof is reduced. The effect of the secondary field is thereby also reduced and a particularly linear response and a reduction in harmonic distortion can thereby be achieved. |
