Patent ID: 8385583

Claim:
A balanced armature apparatus, comprising: a first permanent magnet; a second permanent magnet; an armature, having an end portion located between the first permanent magnet and the second permanent magnet; and a coil, the coil being magnetically coupled to the armature, the coil being energizable by a drive signal so as to induce a flux level within the armature and a deflection of the end portion of the armature, a displacement relationship relating the displacement to a drive signal level, the armature being configured to have a reluctance that increases with the drive signal level so as to improve linearity of the displacement relationship, for flux levels less than those required to initiate saturation of the entire armature, the armature including a partial saturation portion configured to saturate at a drive signal level less than required to saturate an adjacent portion of the armature, the apparatus further comprising a flanking piece providing a flux shunt around the partial saturation portion when the partial saturation portion is saturated, the flux shunt having a higher reluctance than the partial saturation portion of the first material.