Modeling the Electrical Parameters of a Loudspeaker Motor System with the AC/DC Module

M. Cobianchi [1], M. Rousseau [1], S. Xavier [1],
[1] B&W Group Ltd., Worthing, West Sussex, United Kingdom
Published in 2015

The main purpose of a drive unit is to transform the electrical signal at its terminals into acoustic waves via two transduction mechanisms: electro-mechanical and mechano-acoustical. In this paper only the electro-mechanical transformation is discussed in view of a future optimization of the main electrical parameters for a loudspeaker motor: the Force Factor (Bl) and the Blocked Impedance (Zb) as functions of the voice coil position.

The COMSOL Multiphysics® model is described and then compared to a similar implementation in the software FEMM (Finite Element Method Magnetics). The experimental validation of the model is presented by comparing the "Force Factor (Bl)" and "Blocked Impedance” versus displacement curves to these quantities measured with a tensile test machine (quasi-static setup) and the Klippel DA (dynamic setup).