微型喇叭之研製

Abstract

本文研究並設計一微型喇叭，其中包含一動圈式激震器、懸邊、及振膜。在動圈式的激震器中，主要包含有音圈及磁體二個部分，磁體部分將焦點放在內磁式的磁體，將磁體的結構細分出來，探討磁體中氣隙磁場的變化趨勢及其漏磁狀況。當喇叭在發聲時，此時音圈因為受力而上下來回振動，本文將探討此動態時的受力狀況及其振幅。由於喇叭的尺寸小，為使激震器具有較大的推力及效率，而使喇叭發出較大的音量，本文在理論部分利用有限單元方法研究激震器磁體的磁力分布，探討氣隙磁場與磁體尺寸參數間的關係，以磁力線圖來探討磁體之漏磁狀況；並以迴歸方法，找到一個關於漏磁係數及氣隙磁通密度的方程式。然後將喇叭系統化成單一自由度的模型，探討喇叭之振幅及激震器出力的上下限。最後從聲壓曲線之觀點，來探討喇叭的特性。

This paper is focused on the design and fabrication of a small loudspeakers with moving coil type exciter, suspension, and diaphragm. A moving coil type exciter includes a voice coil and a magnet center-mount assembly. We analyze the magnetic flux distribution and flux leakage inside the exciter by subdividing the magnet assembly construction. When the loudspeaker is working, the diaphram is vibrating by the output force of exciter. We analyze the output force and the amplitude at this time. Because of the output volume of sound from the loudspeaker is directly proportional to the output force from the exciter, and the output force of the exciter depends on the flux density in the air gap of the magnet assembly of the exciter. In this thesis we analyze the flux distribution in the air gap of the magnet assembly of the exciter using a 2-D finite element model. Then we analyze the amplitude of the loudspeaker, and the output force limit of the exciter using a one degree of freedom vibration system. Several loudspeakers composed of a exciter, a diaphragm, and suspension are made. The loudspeaker performance are conducted by measuring their SPL curves for comparison.