扬声器直流偏置产生机理研究及其估算方法

直流偏置会对扬声器性能造成不良影响。研究了扬声器驱动力系数、劲度系数和电感等主要非线性特性与所对应的驱动力、回复力和磁阻力中的直流分量的相互关系，进而分析了这些力的直流分量所导致音圈位移直流偏置。提出了一种基于集总参数模型(Lumped Parameter Model, LPM)的扬声器直流偏置估算方法，它先通过数值仿真分析方法(或测量方法)得到扬声器的驱动系数Bl(x)、劲度系数K(x)和电感L(x)等非线性参数，再将它们代入到LPM模型，求解该模型得到位移时域响应，并进一步后处理得到直流偏置。采用该方法估算了一款6.5 in(1 in=2.54 cm)汽车扬声器和一款2 in全频带扬声器的直流偏置，并分析了它们的非线性参数对直流偏置的影响。扬声器样品直流偏置的实测结果表明，估算曲线与实测曲线趋势基本一致。合理调整非线性参数，可调整或减小直流偏置，进而优化设计高品质的扬声器。

Research on generation mechanism of loudspeaker DC offset and its estimation method

Direct current (DC) offset has undesirable influence on loudspeaker performance. The relationships of the main nonlinear characteristics of loudspeaker, such as force factor, stiffness coefficient and inductance, with the DC components in the corresponding driving force, recovery force and magnetic resistance are studied. Then the DC components of voice coil displacement caused by the DC components of these forces are analyzed. A loudspeaker DC offset estimation method based on lumped parameter model (LPM) is proposed. Firstly, the nonlinear parameters such as Bl(x), K (x) and L (x) of loudspeaker are obtained based on numerical simulation analyses or measurements, and then they are substituted into the LPM model. The displacement response is calculated by solving the model, and the DC offset is obtained by further post-processing. By using this method, the DC offsets of a 6.5 in (1 in=2.54 cm) automobile loudspeaker and a 2 in full range loudspeaker are estimated, and the influences of various nonlinear parameters on the DC offset are analyzed. The measurement results of speaker DC offset show that the trends of the estimated curves are basically consistent with the measured curves. By properly adjusting the nonlinear parameters, the DC offset can be adjusted or reduced, thus optimize the design of high-quality speakers.