An integrated circuit for implementing at least a portion of a personal audio system, comprising: a source of audio for reproduction, wherein the source of audio provides a source audio signal; a first output for providing a first output signal to a first transducer (SPKRH) for reproducing high-frequency content of the source audio signal and a first anti-noise signal (anti-noiserh) for countering the effects of ambient audio sounds in an acoustic output of the first transducer (SPKRH); a second output for providing a second output signal to a second transducer (SPKRL) for reproducing low-frequency content of the source audio signal for playback to a listener and a second anti-noise signal (anti-noiseri) for countering the effects of ambient audio sounds in an acoustic output of the second transducer (SPKRL); at least one microphone input for providing at least one microphone signal indicative of the ambient audio sounds; and a processing circuit that generates the first anti-noise signal (anti-noiserh) from the at least one microphone signal (ref) using a first filter to reduce the presence of the ambient audio sounds at the first transducer (SPKRH) and the second transducer (SPKRL) in conformity with the at least one microphone signal, wherein the processing circuit generates the second anti-noise signal (anti-noiseri) from the at least one microphone signal (ref) using a second filter to reduce the presence of the ambient audio sounds at the first transducer (SPKRH) and the second transducer (SPKRL) in conformity with the at least one microphone signal (ref), characterised in that the first filter is a first adaptive filter having a first response that adapts to reduce the presence of the ambient audio sounds, and wherein the second filter is a second adaptive filter that adapts to reduce the presence of the ambient audio sounds, wherein the processing circuit restricts content of the first anti-noise signal (anti-noiserh) to a first predetermined frequency range by limiting the first frequency response of the first adaptive filter to a first predetermined frequency range, and wherein the processing circuit restricts content of the second anti-noise signal (SPKRH) to a second predetermined frequency range by limiting the second response of the second adaptive filter to a second predetermined frequency range, wherein the first predetermined frequency range and the second predetermined frequency range are substantially different, whereby the first adaptive filter and the second adaptive filter operate as cross-over for separating the at least one microphone signal (ref) into multiple frequency bands. a source of audio for reproduction, wherein the source of audio provides a source audio signal; a first output for providing a first output signal to a first transducer (SPKRH) for reproducing high-frequency content of the source audio signal and a first anti-noise signal (anti-noiserh) for countering the effects of ambient audio sounds in an acoustic output of the first transducer (SPKRH); a second output for providing a second output signal to a second transducer (SPKRL) for reproducing low-frequency content of the source audio signal for playback to a listener and a second anti-noise signal (anti-noiseri) for countering the effects of ambient audio sounds in an acoustic output of the second transducer (SPKRL); at least one microphone input for providing at least one microphone signal indicative of the ambient audio sounds; and a processing circuit that generates the first anti-noise signal (anti-noiserh) from the at least one microphone signal (ref) using a first filter to reduce the presence of the ambient audio sounds at the first transducer (SPKRH) and the second transducer (SPKRL) in conformity with the at least one microphone signal, wherein the processing circuit generates the second anti-noise signal (anti-noiseri) from the at least one microphone signal (ref) using a second filter to reduce the presence of the ambient audio sounds at the first transducer (SPKRH) and the second transducer (SPKRL) in conformity with the at least one microphone signal (ref), characterised in that the first filter is a first adaptive filter having a first response that adapts to reduce the presence of the ambient audio sounds, and wherein the second filter is a second adaptive filter that adapts to reduce the presence of the ambient audio sounds, wherein the processing circuit restricts content of the first anti-noise signal (anti-noiserh) to a first predetermined frequency range by limiting the first frequency response of the first adaptive filter to a first predetermined frequency range, and wherein the processing circuit restricts content of the second anti-noise signal (SPKRH) to a second predetermined frequency range by limiting the second response of the second adaptive filter to a second predetermined frequency range, wherein the first predetermined frequency range and the second predetermined frequency range are substantially different, whereby the first adaptive filter and the second adaptive filter operate as cross-over for separating the at least one microphone signal (ref) into multiple frequency bands.