Practical Design of a Speaker Box With a Passive Vibrator (February 2018)

With the rapid development of multimedia devices, such as smart phones and tablet PCs, and wearable devices such as neckband speakers are being used increasingly as audio equipment. Typically, one side of a neckband speaker consists of a microspeaker driver integrated in a speaker box and a linear vibrator independent of the speaker box. In this paper, a practical design of a passive radiator integrated in the speaker box is proposed as a substitute for the linear vibrator. Therefore, both of the microspeaker driver and the passive vibrator are integrated in the speaker box. 2-DOF theory is used to model the system, and parameters are identified using Klippel and the analytical method. The sound pressure is obtained by the boundary element method. First, the prototype of a passive vibrator is built by using a center diaphragm and a side diaphragm. Then, the parameters of the prototypes are determined. An acceleration test is conducted to check the vibrator performance. Finally, an optimized vibrator is manufactured by using the analytical method. The sound pressure level (SPL) and acceleration are determined and conduct a response time experiment. The results show that the SPL values obtained through both of the experiment and simulation show good agreement and that there is only 2 dB sacrificed owing to the passive vibrator. The acceleration experiment results show that the optimized passive vibrator can generate 1.5 Grms at 130 Hz; this represents an improvement of 60% compared with the prototype. Furthermore, the response time of the passive vibrator is 20 ms. The proposed passive vibrator can be used to develop commercial neckband speakers.