The influence of diaphragm shape on loudspeaker directivity has been evaluated only in the frontal half-space in studies using infinite baffle models, and thus, information in the rear field remains unknown. To extend the result to the entire space, a spherical-enclosure loudspeaker model (SELM) is used in this paper that is based on modifications of existing rigid-sphere loudspeaker models. Using the boundary element method, the radiation of the SELM is simulated in the full audible range, and then directivities for dome-shaped diaphragms with different relative heights (RHs) are compared and analyzed using various metrics. The results show that in general, the planar diaphragm exhibits narrower directivity than convex or concave domes, whereas directivities of the latter two change differently with RH. In the case of a concave hemisphere, a resonance occurs around ka0 = 7.14 (a0 is the radius of the sphere), causing a low radiation power and an unusual directivity pattern, which agrees with findings of Suzuki and Tichy. For the rear radiation, the rear-to-front difference in sound pressure level of the convex hemisphere does not exceed 10 dB in the whole audible range, indicating that its rear radiation should not be neglected even in high frequencies.
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