The effect of negative source impedance on the frequency response and pole-zero pattern of a moving coil loudspeaker drive unit is explored from first principles, and closed form expressions for the transfer function and system poles are developed. Direct control of motor velocity via the substantial cancellation of voice coil impedance is discussed. Implementation using positive current feedback is analyzed, considering loop gain, damping and stability from a control theory perspective. Pole placement techniques are shown to be effective in controlling theoretical system behavior at high frequencies. Modeled and measured results are presented. A selection of previous papers and applications concerned with operation of loudspeakers from negative source impedances is briefly reviewed. Practical issues and some possible applications are discussed.

Authors: Turner, Michael J.; Wilson, David A.
Affiliations: University of Leeds; S.R. Drives Ltd.(See document for exact affiliation information.)
AES Convention: 122 (May 2007) Paper Number: 7072
Publication Date: May 1, 2007 Import into BibTeX
Subject: Microphones and Loudspeakers
Permalink: https://www.aes.org/e-lib/browse.cfm?elib=14057

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