| Summary: | 碩士 === 國立交通大學 === 機械工程系所 === 97 === A push-pull electret loudspeaker is a flat type loudspeaker, and it is made with the thin and light electret material. The absence of low frequency response is a defect of the push-pull electret loudspeaker. Therefore, the subwoofer system is adopted to recover the low frequency response. The combination of the push-pull electret loudspeaker and the subwoofer can provide a complete audio system.
Via the electrical impedance measurement, the curve fitting and added mass method, the T-S parameters of the subwoofer can be identified. The conventional lumped parameter model of the subwoofer can be established using the EMA analogous circuit and T-S parameters. Next, the conventional lumped parameter model is employed to the simulation of vented-box system. The constrained optimization technology was also employed to find the design that can enhance the low frequency response of the vented-box system.
The push-pull electret loudspeaker is also analyzed in this thesis. A fully experimental modeling technique and a design optimization procedure are presented for push-pull electret loudspeakers. Conventional electrical impedance-based parameter identification methods are not completely applicable to electret speakers due to the extremely weak electromechanical coupling. This prompts the development of a new experimental technique for identifying the electroacoustic parameters of the electret speakers. Mechanical parameters are identified from the membrane velocity measured using a laser vibrometer. The voltage-force conversion factor and the motional impedance are estimated, with the aid of a test-box method. This experimentally identified model serves as the simulation platform for predicting the response of the electret loudspeaker and optimizing the design. Optimal parameters are calculated by using the simulated annealing (SA) algorithm to fulfill various design goals and constraints. Either the comprehensive search for various parameters or the simple search for the optimal gap distance can be conducted by this SA procedure. The results reveal that the optimized design has effectively enhanced the performance of the electret loudspeaker.
|
|---|
