The effects of box design on the transient response of a loudspeaker

• Main Authors: Yu-Hou Lin, 林昱豪
• Other Authors: Chan-Nan Wang
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/47467291327358428042

碩士 === 國立臺灣大學 === 工程科學及海洋工程學研究所 === 103 === This thesis is used of equivalent circuit method to simulate the displacement curve of the loudspeaker diaphragm, then using short-time Fourier transform to make time domain displacement curve convert to the time-frequency domain. Then interception of the energy data on resonance frequency that decay with time and then plot the decay curve. Finally, this curve will determine the transient response of the loudspeaker system is good or bad. This thesis consists of two parts. First, by equivalent circuit method, the loudspeaker system could be simplified to electro-mechano-acoustic analogous circuits, then using these three equivalent circuits to derive three equations. By solving these equations, the simulated displacement curve of the loudspeaker system could be calculated. Furthermore, time domain displacement was converted to time-frequency domain through Matlab software. Then the energy points on resonance frequency can be intercepted on the time-frequency spectrum. Finally, the time constant of the curve would be calculated to determine the performance of transient response. The shorter it is, the better transient response is. Second, produce a loudspeaker system by using Applied Acoustics’s equipment so that we could measure the displacement curve of the system, then the data processing would be imported by using Matlab software. Finally, Time constant would be compared with the simulation results. The results showed that the size of the closed box does not affect the transient response of the loudspeaker. For vented-box loudspeaker system: the transient response must be enhanced if we reduced the diameter or length of the tube. For six-order loudspeaker system, the performance of transient response depended on diameter of outside tube, the shorter it is, the better transient response is. Finally, these results can be used as guidelines to improve the transient response of the loudspeaker.