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A Study of Low-Frequency Near- and Far-Field Loudspeaker Behavior

Low-frequency loudspeaker measurements are difficult. Room reflections, mediocre anechoic chambers, and random noise play havoc with the quest. Diffraction is different in nearfield and farfield. This paper covers a range of topics that bear on these problems, such as boundary element diffraction simulations, an approximate theory for low frequencies, methods to shorten the impulse response, and nearfield characteristics. A few points are illustrated with measurements. An earlier simplified diffraction theory of Kessel is checked for axisymmetric cylindrical and rectangular boxes by boundary-element simulations, in an attempt to pin down the diffractive 4pi>2pi transition. It turns out to have a strong connection to the acoustic centre of a loudspeaker. Some measurements are made under various conditions. Shortening methods are used to minimize the deleterious effect of truncating room reflections from the impulse response.

Authors: Vanderkooy, John; Rousseau, Martial
Affiliations: University of Waterloo, Waterloo, Ontario, Canada; B&W Group Ltd., Steyning, West Sussex, UK(See document for exact affiliation information.)
AES Convention:126 (May 2009) Paper Number:7747 Import into BibTeX
Subject:Room Acoustics & Loudspeaker Interaction

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