Optimization of Microspeaker Diaphragm Pattern Using Combined Finite Element-Lumped Parameter Models

Abstract

Microspeakers in portable devices are expected to meet a number of conflicting requirements such as miniaturization, high output level, and good sound quality. In contrast to large loudspeakers, the structures of microspeakers are generally simplified by removal of the suspension. The diaphragm serves as not only a sound radiator but also the suspension. Thus, the pattern design of the diaphragm is crucial to the overall response and performance of a microspeaker. The traditional approach for modeling microspeakers using lumped parameter models is generally incapable of modeling flexural modes in high frequencies. In this paper, we present a hybrid approach that combines finite-element analysis (FEA) and electro-mechano-acoustical (EMA) analogous circuit to provide a more accurate model than the conventional approaches. In particular, the minute details of diaphragms are taken into account in calculating the mechanical impedance of the diaphragm-voice coil assembly using FEA. The mechanical impedance is then incorporated into the lumped parameter model. The responses can be simulated by solving the loop equations. On the basis of this simulation model, we optimize the pattern design of the diaphragm using the Taguchi method. In addition, we determine the optimal number of diaphragm corrugations by using sensitivity analysis.