臺灣博碩士論文加值系統

本研究運用音響測試分析軟體ARTA來進行揚聲器單體頻率響應、Thiele/Small參數測量及計算，再以WinISD Pro軟體計算低音反射式揚聲器系統之箱體容積與導管長度與直徑，並模擬頻響應。

音箱的容箱和導管提供了特定的阻尼與自然共振，與揚聲器單體的Thiele/Small參數間控制著揚聲系統的頻率響應曲線與效率，然而理論的分析結果可能需要實驗進行測試與微調才可獲得最佳之結果。本研究藉著改變低音反射導管長度以調整音箱阻尼與自然共振頻率，以ARTA對設計後的固定容積揚聲系統進行阻抗與頻率響應測試，並探討導管、喇叭阻抗與頻率響應間的關係，並歸納出較佳的揚聲系統設計參數。

凹陷濾波器是現代高階喇叭必備的調音利器，要找到頻率響應非常平坦的揚聲器非常不容易，而且價格昂貴，以凹陷濾波器將頻率響應圖中凸起部份經由波段濾波使頻率響應較為平坦，則是以較低價格即可獲得頻率響應較佳之揚聲器系統的一種好方法。本研究並設計了一併聯一階衰減凹陷濾波器，運用於一揚聲系統以消除揚聲系統中在500 Hz到2000 Hz間的凸起。測試結果顯示凹陷濾波器將原頻率響應圖中800 Hz到1600 Hz間凸起約8dB的階段降低了約4dB，但由於濾波器係一階衰減，因此在500 Hz和2000 Hz處也被衰減了約2 dB，因此對讓頻率響應平坦化的功能不明顯，且串聯於擴大機與揚聲器間，揚聲器整體效率也稍受影響而降低。故設計凹陷濾波器時，其設計頻率、串聯或併聯及其衰減程度都是成功設計的考慮因素。

In this research the ARTA software, a collection of programs for audio measurements and analysis, was used to measure the frequency response and the Thiele/Small parameters for loudspeaker drivers. The WinISD Pro software was used to calculate the box volume and the vent tube of a vented cabinet system for designated speaker drivers. Frequency responses were simulated.

For a vented loudspeaker cabinet, resonant frequency and damping factor were dominated by the volume and the geometry of the vent tube. The cabinet’s resonant frequency, damping factor and the loudspeaker driver’s Thiele/Small parameters determine the frequency response and efficiency of the loudspeaker system. To achieve the best result for a loudspeaker system, experiments and adjustments may be needed in addition to the theoretical analysis. In order to study influences of the resonant frequency and the damping factor on the impedance and the frequency response, a loudspeaker system with different lengths of the round vent tubes for a fixed volume cabinet was tested. By comparing the measured results, relationships between vent tubes, impedance curves and frequency responses curves were discussed. Better design parameters were therefore suggested.

Notch filter is considered as a good tool for designing a modern high-end loudspeaker. To find a loudspeaker driver with flat frequency response is very difficult and the driver could be implausibly expensive. Notch filter, used to remove the rise in the frequency curve for a specified stopband, is an excellent and budget way for a loudspeaker system to achieve flatter frequency response. In this research, a parallel notch filter was designed for the experimental loudspeaker system to attenuate the rise between 500 Hz and 2000 Hz. Experiments showed that the notch filter has attenuated the curve between 800 Hz and 1600 Hz for about 4 dB. Since only the first order of decaying was used for the filter, frequency response at 500 Hz and 2000 Hz also have been attenuated for about 2 dB. This means that filter’s function to flatten the frequency response is not very effective. Meanwhile the filter, serially connected between the amplifier and the loudspeaker, has also acted as an factor to lower the loudspeaker’s efficiency during the most musical range. Therefore to successfully design a notch filter, the stopband, parallel or serial schematics, and the order of attenuation are important factors to consider.

致謝 iii
摘要 iv
Abstract vi
目錄 viii
表圖目錄 x
第一章 緒論 1
1.1前言 1
1.2研究動機與目的 2
1.3研究背景 3
第二章 揚聲器系統基本理論 5
2.1揚聲器基本參數 5
2.2密閉式音箱 7
2.3低音反射音箱喇叭 8
第三章 揚聲器設計與分析 12
3.1揚聲器阻抗測量 12
1.硬體設定 12
2使用Lamp軟體量測喇叭阻抗 13
3音效卡設定 14
4訊號產生器設定 14
5校準測量 15
6測量設置 15
7開始進行量測 16
3.2揚聲器物理參數分析 17
3.3使用LIMP計算動態喇叭參數 19
3.4音箱最佳化分析與實驗 21
第四章凹陷濾波器 33
4.1凹陷濾波器 33
4.2串聯凹陷濾波器原理 33
4.3並聯凹陷濾波器之原理 36
4.4模擬與實作 38
1.喇叭測試模組： 38
2.ARTA軟體操作 41
3.基本設定 42
4.輸入輸出擴大器介面： 43
5.麥克風設定： 43
6.麥克風電壓估測 44
7.麥克風靈敏度 45
8.頻率響應補償 46
4.5實際量測結果 48
第五章結果與討論 51
參考文獻 52
作者簡介 54

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