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Mechanical Properties of Ferrofluids in Loudspeakers

This paper describes the mechanical properties of ferrofluid seals in ironless electrodynamic loudspeakers. The motor is constituted of several outer stacked ring permanent magnets. The inner moving part is a piston. In addition, two ferrofluid seals are used which replace the classical suspension. Indeed, these seals fulfill several functions. First, they ensure the airtightness between the loudspeaker faces. Second, they act as bearings and center the moving part. Finally, the ferrofluid seals also exert a pull back force on the moving piston. Both radial and axial forces exerted on the piston are calculated thanks to analytical formulations. Furthermore, the shape of the seal is discussed as well as the optimal quantity of ferrofluid. The seal capacity is also calculated.

Authors: Lemarquand, Guy; Ravaud, Romain; Lemarquand, Valerie; Depollier, Claude
Affiliation: Université du Maine
AES Convention:125 (October 2008) Paper Number:7533 Import into BibTeX
Subject:Loudspeaker Design

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