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Session A Friday, November 30 9:00 am-11:00 am
Chair: Neil Harris, NXT Research Centre, Huntingdon, Cambridgeshire, UK

9:00 am

A-1  Two-Port Representation of the Junction between Horn Driver and Horn

Gottfried K. Behler and Michael Makarski, Institute of Technical Acoustics, University of Aachen, Aachen, Germany

Horn drivers and horns in general are measured and characterized as combinations only. This is a restriction compared to the possibility of arbitrarily combining the two parts at its standardized connection. With the method presented here, an individual measurement of each part is possible, and the overall transfer characteristics of the combined system is calculated by a computational tool.

Convention Paper 5409


9:30 am

A-2  The Transient Magnetic Behaviour of Loudspeaker Motors

Mark Dodd, Celestion International Ltd., Ipswich, Suffolk, UK

Magneto-static finite-element methods have been applied to designing loudspeaker motors for some time. Advances in both hardware and software present the opportunity of extending our knowledge about the detailed electro-magnetic behavior of loudspeaker motors. In particular by coupling a lumped-element kinematic model to a transient-magnetic finite-element model, the motion of a loudspeaker voice coil may be calculated for an arbitrary electrical input. This motion includes components due to transduction nonlinearities such as flux-modulation, eddy currents, and force factor profile. A great advantage of this technique is that the results show the distribution of eddy currents throughout the structure, allowing their display and analysis. Furthermore, by calculating the motion of a loudspeaker voice coil for a sinusoidal input, the harmonic distortion of the transduction mechanism may be calculated at any chosen level and frequency. Preliminary results from a new motor structure are presented to illustrate some of the benefits and current limitations of this technique.

Convention Paper 5410


10:00 am

A-3  Compensating Non-Linear Distortion in an 'Equal-Hung' Voice Coil

Andrew Bright, DTU, Lyngby, Denmark and Nokia Research Center, Helsinki, Finland

Nonlinear distortion compensation by DSP has been actively researched over the last decade. This paper analyzes the potential benefits such distortion compensation systems may provide in complete electroacoustic systems. Specifically, this paper compares the increase in amplifier output required by such systems with the increase in sensitivity provided by shorter voice coils. It is shown that a net increase in the sensitivity is provided if a loudspeaker's voice coil height is equal to its magnet gap height and used over a range of peak-to-peak excursions equal to three times this height.

Convention Paper 5411


10:30 am

A-4 Spatial Bandwidth of Diffuse Radiation in Distributed Mode Loudspeakers

Neil Harris, NXT Research Centre, Huntingdon, Cambridgeshire, UK
Malcolm O. J. Hawksford, University of Essex, Colchester, Essex, UK

The degree to which radiation from a loudspeaker is diffuse may be quantified by a spatial correlation function normalized to the on-axis response. This is true for any loudspeaker type, including the distributed-mode loudspeaker (DML). However because of the variation in material damping and design-related constraints, correlation commonly varies both with frequency and direction. A modified function, the offset spatial bandwidth of correlation function, is introduced as a means of describing diffuse performance and quantifying its variation over the radiation field.

Convention Paper 5412

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