Patent ID: 8249291

Claim:
An electromagnetic driver for use in an electromagnetic transducer, the electromagnetic driver comprising: an inner magnetic portion held in fixed relationship to an outer magnetic portion so as to form an air gap between the inner magnetic portion and the outer magnetic portion, where the inner magnetic portion is not in physical contact with the outer magnetic portion, the inner magnetic portion including: a ferromagnetic spacer member including a first side, an axially opposite second side, and an axial thickness between the first side and the second side, where the spacer member is ferromagnetic throughout the axial thickness; a first permanent magnet in contact with the first side; a second permanent magnet in contact with the second side; a first pole piece capable of carrying magnetic flux; and a second pole piece capable of carrying magnetic flux, where the first permanent magnet, the spacer member, and the second permanent magnet are located between the first pole piece and the second pole piece; and a coil former, where a portion of the coil former is located within the air gap and capable of a range of axial movement within the air gap, the coil former having a first coil portion and a second coil portion, the coil former with the first coil portion and the second coil portion being adapted to oscillate in response to changes in electric current applied to the first coil portion and the second coil portion while subjected to a magnetic field in the air gap.