Abstract: An audio output system, having loudspeakers with an asymmetrical output in response to symmetrical modulated input signals, is provided with a unidirectional limiting circuit for proportionally reducing input signals of a polarity to drive the loudspeaker in the direction of its greatest response. In its basic form, the limiting circuit is a voltage limiting circuit, preferably a voltage divider, which includes a rectifier device. When the driving signal is of a polarity to produce a greater response from the loudspeaker, the rectifier device conducts and the magnitude of the signal voltage is reduced, resulting in substantially greater uniformity of output response of the loudspeaker in both directions. When the limiting circuit is placed on the input side of the power amplifier, the rectifier device advantageously is a vacuum tube connected as a diode. When located in the output stages of the power amplifier, where higher signal voltages are available, solid state rectifier devices may be employed.