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1

Distortion in Electrodynamic Loudspeakers Caused by Force Factor Variations

Erza M., Lemarquand G., Lemarquand V.

Archives of Acoustics

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2011

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Vol. 36, No. 4

873-885

EN

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.

2

Ranking of the Nonlinearities of Electrodynamic Loudspeakers

Ravaund R., Lemarquand G., Lemarquand V., Roussel T.

Archives of Acoustics

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2010

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Vol. 35, No. 1

49-66

EN

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.

3

Motor Nonlinearities in Electrodynamic Loudspeakers: Modelling and Measurement

Merit B., Lemarquand V., Lemarquand G., Dobrucki A.

Archives of Acoustics

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2009

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Vol. 34, No. 4

579-590

EN

This paper studies the motor nonlinearities of a classical electrodynamic loudspeaker. Measurements show the dependence of the voice-coil inductance with its position and with the driving current as well as the force factor dependence on the coil position. They allow the tuning of the parameters of a model proposed for these dependences. Time and frequency analysis of the model help in the explanation of both the harmonic and intermodulation distortions observed in classical loudspeakers

4

An ironless large displacement flat piston loudspeaker

Remy M., Lemarquand G., Guyader G.

Archives of Acoustics

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2009

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Vol. 34, No. 4

591-599

EN

This paper presents a small wide-band loudspeaker. Particular efforts have been made to reduce the nonlinearities of the loudspeaker as much as possible. The motor structure is completely ironless, the elastomer suspensions are replaced by ferrofluid seals and a monobloc carbon foam piston substitutes the traditional conic membrane. The circular radiating surface, which is flat, has a diameter equal to only 2 cm. Therefore, in order to obtain a sufficient sound pressure level at low frequencies, large displacements of the piston are necessary. After a detailed description of each part of the loudspeaker, theoretical results of the expected performances of this transducer are given.