Magneto-electrodynamical modeling and design of a microspeaker used for mobile phones with considerations of diaphragm corrugation and air closures

Abstract

Recent design trends for modern mobile phones are evolving to be miniaturized and versatile sounds in quality. To these ends, a microspeaker with a corrugated diaphragm is employed to broaden the sound frequency range. Due to the fact that diaphragm corrugation and air closures were not considered in any past studies, this study presents comprehensive modeling with the consideration of diaphragm corrugations and air closures. It starts with the modeling on the subsystems of the voice coil motor (VCM) in the speaker. The magnetic field of the VCM is modeled by one set of finite elements, while the corrugated diaphragm is modeled by another set of finite elements. In addition, the air closures above or below the diaphragm are modeled by the third group of finite elements based on basic acoustics. Simulations are conducted with and without air closures. It is found that: 1) the speaker with 45 degrees corrugation exhibits overall higher (better) sound pressure levels (SPLs), while 2) the 75 degrees corrugation leads to unsatisfied, low SPLs below 1 kHz and two undesired antiresonances at higher frequencies. The theoretical findings are successfully validated by experiments.