An audio system comprising an electro-acoustic transducer having two stacked voice coils mechanically linked to a membrane. The voice coils are oscillatingly suspended in the magnetic field of a permanent magnet focused by a pole plate and are mechanically arranged symmetrical to the pole plate while in a rest position. The audio system further comprises two driver circuits connected to the electro-acoustic transducer.

Some embodiments of the present invention disclose a miniature sounder. The miniature sounder includes a frame, and a vibration system and a magnetic system that are fixedly connected to the frame; the magnetic system includes a lower clamping board, a primary magnet that disposed on the lower clamping board, a cushion that disposed on the lower clamping board and surrounding the primary magnet and a secondary magnet that disposed on the cushion and surrounding the primary magnet, the cushion being disposed between the secondary magnet and the lower clamping board; and the vibration system includes a voice diaphragm, a voice coil that disposed below the voice diaphragm and causing the voice diaphragm to vibrate and generate a sound and a vibration diaphragm elastically supporting the voice coil, the vibration diaphragm comprising a corrugated rim portion, a fixing portion and a connecting portion.

Systems, devices, and methods are described for providing loudspeaker protection. An upstream loudspeaker model estimation component receives sensed electrical characteristics of a loudspeaker and generates an impedance model from which an excursion model, and associated parameters, of the loudspeaker as well as a gain change parameter may be generated. The impedance components are fitted to features of an estimated impedance, based on the voltage and current sense data, to generate the estimated impedance model that is converted to an excursion model of the loudspeaker. A downstream audio signal processing component, based on the excursion model, or parameters thereof, limits a predicted excursion of the loudspeaker utilizing excursion-constraining processing circuitry that includes a non-linear constraint filter. Processed audio signals associated with the limited excursion are subject to distortion suppression prior to releasing the output audio signals for playback on the loudspeaker.

Audio circuitry, comprising: a speaker driver operable to drive a speaker based on a speaker signal; a current monitoring unit operable to monitor a speaker current flowing through the speaker and generate a monitor signal indicative of that current; and a microphone signal generator operable, when external sound is incident on the speaker, to generate a microphone signal representative of the external sound based on the monitor signal and the speaker signal.

Embodiments of the invention provide methods and apparatus for measuring and characterizing a loudspeaker. In particular, the non-linear response of the loudspeaker can be determined. Embodiments of the invention also provide methods and apparatus for processing audio input signals, for example, so as to linearize the output of a given loudspeaker.

Method to perform thermal monitoring of an electro-mechanical actuator included in a device starts by receiving an in-field calibration temperature from a temperature sensor included in the device. The device may also receive an in-field calibration resistance from a resistance calculator included in the device. A calculated thermal coefficient of resistivity of the electro-mechanical actuator is then computed using an equation that relates the calculated thermal coefficient of resistivity to the in-field calibration temperature. The calculated thermal coefficient of resistivity changes based on the in-field calibration temperature. The equation includes parameters that are stored in the device. A temperature estimate of the electro-mechanical actuator is them computed based on the calculated thermal coefficient of resistivity. Other embodiments are also described.

A corrector is configured to transform audio signals to compensate for unwanted distortion characteristics of a loudspeaker. A tuning filter is configured to transform audio signals to incorporate desired distortion characteristics associated with a target loudspeaker. By chaining together the tuning filter and the corrector, an audio signal can be modified so that the loudspeaker, when outputting the audio signal, has response characteristics of the target loudspeaker.

A first signal may be received indicative of audio to be played by a speaker. A second signal may be received which comprises (i) a voice input received by a microphone and (ii) at least a portion of the audio played by the speaker at a same time that the microphone receives the voice input. Based on the first signal, nonlinearities output by the speaker which played the audio may be determined. At least the nonlinearities from the second signal may be removed to output a third signal comprising substantially the voice input received at the microphone.

A loudspeaker assembly may be configured with at least one driver disposed between first and second acoustic impedance structures. The first and second impedance structures can be arranged with one or more layers that have similar, or dissimilar, thicknesses. The first and second impedance structures can respectively be configured to maintain symmetric acoustic impedance on opposite sides of the driver during operation of the driver.

Techniques, methods, systems, and other mechanisms for measuring the excursion of a speaker while being actively driven. Measuring excursion can involve attaching a flexible printed coil (FPC), including a sense coil, to the speaker, and monitoring an induced current as produced though the sense coil, and further detecting that violation of an excursion limit for the speaker may likely occur.