Voice Coil Impedance as a Function of Frequency and Displacement
Mark Dodd, Wolfgang Klippel, Jack Oclee-Brown · Journal of the Audio Engineering Society · 2004
Recent work by Klippel [1] and Voishvillo [2] has shown the significance of voice coil inductance in respect to the non-linear behaviour of loudspeakers. In such work the methods used to derive distortion require the inductance to be represented by an equivalent circuit rather than the frequency domain models of Wright and Leach. A new technique for measurement of displacement and frequency dependant impedance has been introduced. The complex relationship between coil impedance, frequency and displacement has been both measured and modelled, using FE, with exceptional agreement. Results show that the impedance model requires that its parameters vary independently with x to satisfactorily describe all cases. Distortion induced by the variation of impedance with coil displacement is predicted using both parameterised and FE methods, these predictions are compared to measurements of the actual distortion. The nature of this distortion is discussed. Dodd et al. Voice coil impedance Page 2 of 17