微型平衡電樞式揚聲器之電聲分析與設計

Electroacoustic analysis, design, and implementation of small balanced armature speakers

游博丞(Bo-Cheng You)

指導教授 ： 白明憲

國立清華大學/工學院/動力機械工程學系/碩士(2014年)

摘要

摘要
在這篇論文中，將提出一個新型的平衡電樞式揚聲器，其結構是由永久磁鐵、軛鐵、線圈、驅動桿、電樞和金屬薄膜所組成的。電樞的結構設計是這篇論文的重點，其被設計為一個繞著支點旋轉的運動模式，且纏繞線圈的位置與受磁力作用的位置被分成兩側。因為這樣的設計，電樞的長度可以充分地被線圈利用，且可以增加金屬薄膜被推動的距離。此外，揚聲器中的電樞與永久磁鐵間互相作用的關係將在此被討論，我們利用了類比電路的方法，將磁路類比成電路，以利於分析磁力的特性及了解與結構之間的關係。然而，目前該如何模擬此類型揚聲器的性能還尚未被提出，所以在此將建立一種數學模型來模擬其性能。用集中參數法和複合型參數法來模擬此類型揚聲器有何差異也將在此被討論，一般來說，複合型參數法具有更佳的潛力來預測結構的高頻模態，從模擬結果來看，用複合型參數法來模擬的結果比集中參數法更佳符合量測的曲線。

關鍵字

平衡電樞 ； 機電聲模型 ； 有限單元法 ； 磁路分析 ； 結構設計

並列摘要

A novel balanced armature speaker (BAS) composed of permanent magnet circuits, an armature, a coil, a drive rod, a diaphragm, pivots, and a casing is developed. This paper focuses on the armature design that rotates about a pivot with coil on one side and permanent magnetic field on another. This design employs maximum coil length and driving-point excursion. In addition, the magnetic circuit analysis is conducted to calculate the force factor and is used to analysis the magnetic circuits between a permanent magnet and an armature with the adequate magnetic flux to generate the magnetic force. Based on the force factor, the electro-mechano-acoustical (EMA) analogous circuit can be established to build up a simulation platform with a lumped-parameter method or the hybrid approach that combines a lumped parameter model and a mechanical impedance element that is derived from a finite element model. The hybrid approach enables improved prediction of the flexural modes of a membrane, a rod, and an armature. The results demonstrate that the sound pressure response simulated using the hybrid model yields a better match with the measured response than that simulated using the lumped parameter model.

參考文獻

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