Performance comparison between inner and outer permanent magnet type microspeakers used for mobile phones

Abstract

In mobile phones of the multimedia era, microspeakers of high quality sound are essential parts to generate the human voice in speaker phones and MP3 song players. In this article two types of microspeakers, inner permanent magnet (PM) and outer PM type, are analyzed using electromagnetic, mechanical, acoustical, and their coupling analysis. For performance comparison, a voice coil diameter is chosen as a design parameter to change magnet volume and excitation position for both types. With the decreased voice coil diameter of the outer type, magnet volume is increased to produce higher sound pressure level (SPL) and the first resonant mode of the diaphragm is more efficiently excited due to concentrative excitation, resulting in lower and broader frequency range.