片狀彈性支承之設計及應用

Abstract

本文重點分兩部份。第一部份為彈性支承的研製，為解決傳統彈波在大變形下其彈性係數呈非線性變化的問題，製作一碳纖片狀彈性支承，利用最佳化程式對彈性支承之幾何形狀做最佳化設計，使揚聲器系統之最低共振頻率降低，且能夠於大功率下穩定運動。由於本文使用圓形平面揚聲板，其聲壓曲線在中音域1kHz附近有一聲壓落差，因此第二部份將利用立體加勁方式加強揚聲板之剛性，使中音谷發生的位置往高頻移動，以增加揚聲器在中低音域的實效頻寬。在理論分析上，利用有限單元軟體ANSYS研究加勁振動板之振動行為，並比較不同加勁振動板振形與聲壓曲線的影響，找出最適合之加勁長度，並以實驗加以驗證。

Two parts are discussed in the thesis. The first part is the fabrication of the elastic dampers. In order to tackle the nonlinear problem of traditional damper’s translational stiffness, a plate-type elastic damper is developed for flat panel speakers. The shape of the plate-type elastic damper is optimally designed and carbon fiber epoxy composite material is used to make the plate-type elastic damper. The use of the plate-type damper can make the radiating plate vibrate steadily. For a circular flat panel speakers, there is a dip in mid frequency range on the sound pressure level (SPL) curve. Such dip can be harmful to the sound quality of the loudspeaker. Therefore, in the second part of the thesis a method is proposed to increase the plate stiffness and raise the frequency of the dip in mid frequency range. The finite element model of the loudspeaker is constructed through the FE software ANSYS. The mode shapes of the radiating plate with added carbon fiber epoxy stiffeners are analyzed using ANSYS. The appropriate lengths of the stiffeners are determined to expand the low to mid frequency range with flat response on the SPL curve. Experiments are performed to verify the feasibility of the proposed design method in the design of circular flat panel loudspeakers.