This paper addresses various aspects on the realization of dedicated pulse-width modulation (PWM) based amplifiers for active loudspeaker systems, optimized in respect to energy consumption. A new amplifier concept, dedicated to woofer/: midrange (0-4.5-kHz) loads, has been developed. The concept is based on a novel feedback topology, a modulation strategy that is dependent of bandwidth and the use of a switching frequency as low as 44.1 kHz without compromising the sound quality. Detailed measurements on a 250-W example implementation are given. THD+N <0.1% is realized at all output powers and frequencies, and the reduction in energy consumption is around 90% compared with an equivalent conventional Class-AB amplifier.
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