Abstract
A novel balanced armature speaker (BAS) composed of permanent magnet circuits, an armature, a coil, a drive rod, a diaphragm, pivots, and a casing is developed. This paper focuses on the armature design that rotates about a pivot with coil on one side and permanent magnetic field on another. This design employs maximum coil length and driving-point excursion. In addition, the magnetic circuit analysis is conducted to calculate the force factor and is used to analysis the magnetic circuits between a permanent magnet and an armature with the adequate magnetic flux to generate the magnetic force. Based on the force factor, the electro-mechano-acoustical (EMA) analogous circuit can be established to build up a simulation platform with a lumped-parameter method or the hybrid approach that combines a lumped parameter model and a mechanical impedance element that is derived from a finite element model. The hybrid approach enables improved prediction of the flexural modes of a membrane, a rod, and an armature. The results demonstrate that the sound pressure response simulated using the hybrid model yields a better match with the measured response than that simulated using the lumped parameter model.