If the excursion limit of the diaphragm of a speaker is exceeded, the speaker exhibits nonlinear behavior which manifests as distorted sound and degraded acoustic echo cancelation (AEC) performance. Moreover, if a speaker is driven too hard, the resulting excessive heat can damage the voice-coil and speaker. While the aforementioned problems are present in speakers of all sizes, these become more acute for smaller, portable speakers, e.g., as used in smartphones, smart speakers, micro-speaker, wearable devices, etc.
This disclosure describes techniques to simultaneously protect the speaker and achieve an optimum, multi-band audio experience by modeling the speaker, dynamically adjusting the excursion, and driving the speaker to its true limit while avoiding non-linear distortion. Per the techniques, real-time variations in the speaker are directly sensed, and feedforward and feedback control procedures are applied to deliver an optimum sound performance while maintaining safe speaker operating conditions.
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Anonymous, "Multiband Speaker Protection and Dynamic Excursion Control of Audio Devices", Technical Disclosure Commons, (August 14, 2020)