Loudspeaker Voice-Coil Inductance Losses: Circuit Models, Parameter Estimation, and Effect on Frequency Response

When the series resistance is separated and treated as a separate element, it is shown that losses in an inductor require the ratio of the flux to mmf in the core to be frequency dependent. For small-signal operation, this dependence leads to a circuit model composed of a lossless inductor and a resistor in parallel, both of which are frequency dependent. Mathematical expressions for these elements are derived under the assumption that the ratio of core flux to mmf varies as ωn−1, where n is a constant. A linear regression technique is described for extracting the model parameters from measured data. Experimental data are presented to justify the model for the lossy inductance of a loudspeaker voice coil. A SPICE example is presented to illustrate the effects of voice-coil inductor losses on the frequency response of a typical driver.