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Acoustic Transparency of Electrostatic Loudspeaker Assemblies

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Although electrostatic loudspeakers (ESL) are renowned for their mid- and high-frequency clarity and coherence, the acoustic behavior of ESL assemblies at high audio frequencies is not well understood. This paper collates acoustic models of all ESL components, including an improved model of perforated-plate stators, and compiles a high-frequency model of the complete ESL assembly. The ESL model includes the membrane, the two perforated-plate stators, the damping cloth, and any grills or dustcovers. The collective behavior of the components is found to be very different from the sum of the effects of each component because of the reflections that occur between the surfaces of all of the components. Therefore, the response of an ESL at high frequencies cannot be determined solely from the attributes of the components taken in isolation. The model shows that the high-frequency response of the ESL is dominated by the effects of inter-component reflections. The distances between the various reflecting surfaces and the overall thickness of the assembly should be minimized to ensure the peaks and dips in the response occur at the highest frequencies. Despite its complexity, the model is easily evaluated numerically with SPICE software, and comparisons with measurements show the model provides a good guide for ESL design. This paper demonstrates a method for measuring the transparency.

JAES Volume 65 Issue 6 pp. 497-506; June 2017
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