Efforts to improve loudspeaker performance in two areas are discussed: (1) the range of listener positions over which accurate, stable stereo imaging is available, and (2) the uniformity of radiation pattern with frequency. These problems are interdependent: solution of the former appears to require solution of the latter. Described is the design of a loudspeaker system that yields stabilized imaging over a wide range of listener positions, a consistent radiation pattern across the audio band, flat frequency and power response from 20 Hz to 20kHz, high power-handling capability and acoustical output, reasonable efficiency, comparatively resistive input impedance, and low distortion. In part the design is based on a listening experiment, also described, to determine the readiation pattern of optimal image stability: an oval. Also described is a computer optimization routine employed to design a phased array of 14 dynamic drivers per cabinet to implement this radiation pattern from 200 Hz. There are associated low- and high-level equalization and processing. Following commercial realization, a second design, closely similar to the first but with 8 drivers per cabinet, has been realized, and the first design has undergone revision as well. More recently, designs with 4, 5, and 6 drivers per cabinet, respectively, have been realized to produce most of the forward half of the oval radiation pattern only. Measurements, listening tests, and independent reviews indicate that the design goals have been substantially met.
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