A parametric equalizer includes an equalizer circuit, a first protection circuit, a second protection circuit, and a first addition circuit. The equalizer circuit is arranged to receive an input signal, and process the input signal to generate an output signal. The first protection circuit is arranged to generate a first protection signal according to the output signal, the input signal, and a first processed signal. The second protection circuit is arranged to generate a second protection signal according to the input signal and a second processed signal. The first addition circuit is coupled to the first protection circuit and the second protection circuit, and is arranged to combine the first protection signal and the second protection signal to generate an equalizer output signal.

A leveling equalizer includes a graphic equalizer circuit, a first multiplication circuit, a second multiplication circuit, an addition circuit, and a gain control circuit. The graphic equalizer circuit processes a first input signal and output a first output signal and a second output signal. The first multiplication circuit multiplies the first output signal and one of an adjustable gain value and a fixed gain value to generate a first adjusted output signal. The second multiplication circuit multiplies the second output signal and another of the adjustable gain value and the fixed gain value to generate a second adjusted output signal. The addition circuit combines the first adjusted output signal and the second adjusted output signal to generate an equalizer output signal. The gain control circuit dynamically adjusts the adjustable gain value according to the equalizer output signal.

In various applications, the system provides a method for processing audio signals, including: receiving a request for audio content; receiving an identifier encoded in a personal audio device comprising a transducer for playing audio; retrieving at least one parameter associated with the identifier; and processing the audio content using at least the request, the identifier and the at least one parameter, wherein the processing is customized for the personal audio device based on the at least one parameter associated with the identifier. In various applications the parameter is, one or more of, associated with a specification of the personal audio device, acoustic metrics of the transducer, relates to control of equalization, relates to permission to enable proprietary sonic processing for enhanced acoustic reception of streaming content, relates to acoustic metrics of the transducer and wherein the identifier is associated with permission to enable proprietary sonic processing for enhanced acoustic reception of streaming content, and/or is stored in a chip on the personal audio device, is retrieved from a server in a network, among other things. In various applications, the personal audio device comprises ear buds and the identifier is stored in a non-volatile memory of the ear buds.

In various applications, the system provides a method for processing audio signals, including: receiving a request for audio content; receiving an identifier encoded in a personal audio device comprising a transducer for playing audio; retrieving at least one parameter associated with the identifier; and processing the audio content using at least the request, the identifier and the at least one parameter, wherein the processing is customized for the personal audio device based on the at least one parameter associated with the identifier. In various applications the parameter is, one or more of, associated with a specification of the personal audio device, acoustic metrics of the transducer, relates to control of equalization, relates to permission to enable proprietary sonic processing for enhanced acoustic reception of streaming content, relates to acoustic metrics of the transducer and wherein the identifier is associated with permission to enable proprietary sonic processing for enhanced acoustic reception of streaming content, and/or is stored in a chip on the personal audio device, is retrieved from a server in a network, among other things. In various applications, the personal audio device comprises ear buds and the identifier is stored in a non-volatile memory of the ear buds.

Embodiments described herein provide for smart configuration of audio settings for a playback device. According to an embodiment, while a playback device is a part of a first zone group that includes the playback device and at least one first playback device, the playback device applies a first audio setting. The embodiment also includes the playback device joining a second zone group that includes the playback device and at least one second playback device. The embodiment further includes the playback device applying a second audio setting based on an audio content profile corresponding to the second zone group.

Methods and apparatus for harmonic source enhancement are disclosed herein. An example apparatus includes an interface to receive a media signal. The example apparatus also includes a harmonic source enhancer to determine a magnitude spectrogram of audio corresponding to the media signal; generate a time-frequency mask based on the magnitude spectrogram; and apply the time-frequency mask to the magnitude spectrogram to enhance a harmonic source of the media signal.

An amplifier stage uses a loaded transistor amplifier circuit including a load that causes greater second order harmonic distortion energy than third order harmonic distortion energy to be produced in said loaded transistor amplifier circuit for amplifying a source audio signal to produce an audio output signal. The spectrum of the fundamental orders of harmonic distortion is adjusted to improve perceived sound quality or listening enjoyment.

An amplifier stage uses a loaded transistor amplifier circuit including a load that causes greater second order harmonic distortion energy than third order harmonic distortion energy to be produced in said loaded transistor amplifier circuit for amplifying a source audio signal to produce an audio output signal. The spectrum of the fundamental orders of harmonic distortion is adjusted to improve perceived sound quality or listening enjoyment.

Certain embodiments provide methods and systems for managing a sound profile. An example playback device includes a network interface and a non-transitory computer readable storage medium having stored therein instructions executable by the processor. When executed by the processor, the instructions are to configure the playback device to receive, via the network interface over a local area network (LAN) from a controller device, an instruction. The example playback device is to obtain, based on the instruction, via the network interface from a location outside of the LAN, data comprising a sound profile. The example playback device is to update one or more parameters at the playback device based on the sound profile. The example playback device is to play back an audio signal according to the sound profile.

A parametric equalizer includes an equalizer circuit, a first protection circuit, a second protection circuit, and a first addition circuit. The equalizer circuit is arranged to receive an input signal, and process the input signal to generate an output signal. The first protection circuit is arranged to generate a first protection signal according to the output signal, the input signal, and a first processed signal. The second protection circuit is arranged to generate a second protection signal according to the input signal and a second processed signal. The first addition circuit is coupled to the first protection circuit and the second protection circuit, and is arranged to combine the first protection signal and the second protection signal to generate an equalizer output signal.