A new low-frequency loudspeaker driver is presented which overcomes many deficiencies of traditional voice-coil drivers. This driver incorporates a low-inertia DC servomotor to provide large, linear excursion. The electroacoustic circuit model and the corresponding Thiele-Small parameters are developed for the servomotor driver and are compared to the voice-coil drivers. Although servomotors possess some inherent nonlinearities at low levels, the overall behavior is linear, especially at large amplitudes when voice-coil drivers are nonlinear. An array of six horn-loaded servomotor loudspeakers has an efficiency exceeding 40% and delivers more than 900 acoustic watts between 31 Hz and 125 Hz.
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