Development of woofer microspeakers used for cellular phones

For cellular phones, high-performance microspeakers with broader frequency range are essential parts to realize various multimedia functions such as MP3 playback, speaker phones, and 64 polyharmonic melody. The operating frequency range of conventional microspeaker ranges is from 800 Hz to 10 kHz. It is very difficult to generate a lower frequency sound below 800 Hz in microspeakers. Therefore, it is necessary to develop woofer microspeakers that make higher sound pressure level (SPL) at a lower frequency band. However, in the case of microspeakers, it is hard to have good performance at a lower frequency range due to size. In this paper, a diaphragm is introduced which is attached to a copper plate to make high performance at a lower frequency range. The woofer microspeaker is developed to have high flux density by magnetic circuit with two-magnet.