The non linearities in the motor of an electrodynamic loudspeaker are still a discussed topic. This paper studies the influence of the force factor variation with the coil displacement on the harmonic and inter-modulation distortions. The real variation is described at least by a linear and a quadratic term. The effect of each term is studied separately, as they don't influence the same kind of frequencies, harmonics or inter-modulation. Both terms considered together result in enhanced effects. The dissymmetry of the Bl variation with regard to the coil centered position has also peculiar effects. This paper presents the method developed to calculate the power of each harmonic and inter-modulation frequency. This allows to compare the obtained values and thus the induced nonlinearities.
The aim of this paper is to present a way of ranking the nonlinearities of electrodynamic loudspeakers. For this purpose, we have constructed a nonlinear analytic model which takes into account the variations of the small signal parameters. The determination of these variations is based on a very precise measurement of the electrical impedance of the electrodynamic loudspeaker. First, we present the experimental method to identify the variations of these parameters, then we propose to study theoretically the importance of these nonlinearities according to the input level or the input frequency. We show that the parameter which creates most of the distortions is not always the same and depends mainly on both the input level and the input frequency. Such results can be very useful for optimization of electrodynamic loudspeakers.