Multiband Loudspeaker Excursion Control With Real-Time Feedback
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Solution Overview
Problem
Existing loudspeaker excursion protection systems fail to account for real-time operational characteristics, leading to issues like volume 'pumping', loss of bass response, and distortion, as they often require pre-calibrated multiband compressor thresholds and do not adapt to changing conditions.
Innovation Solution
An excursion protection system using a feedback signal to perform compression on selected bands in a transform domain, which includes a transformer, excursion transfer function estimator, multiband compressor, amplifier, transformer, excursion predictor, and attenuator, to dynamically adjust gains based on real-time voltage and current information and predict excursion limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wideband limiting is used to limit excursion, then excursion is constrained, but volume pumping, loss of bass response, and distortion occur
Solution Approach 1:
The patent divides the audio spectrum into multiple frequency bands and applies independent compression thresholds to each band. This segmentation allows selective attenuation of frequencies that cause excursion while preserving other frequency ranges, thereby avoiding the harmful effects of wideband limiting such as loss of bass response and distortion.
Solution Approach 2:
The patent applies different compression characteristics to different frequency bands based on their individual contribution to excursion. Each band has its own compression threshold and ratio, allowing localized control over which frequencies are attenuated. This local quality approach prevents uniform volume pumping across all frequencies and maintains natural sound reproduction.
2Reliability
If pre-determined compression thresholds are used in multiband compression, then excursion protection is provided, but the system does not adapt to real-time changes in loudspeaker characteristics
Solution Approach 1:
The patent implements a feedback mechanism that continuously monitors loudspeaker impedance and other operational parameters in real-time. Based on this feedback, the system dynamically adjusts compression thresholds and other parameters to match the current state of the loudspeaker, ensuring optimal excursion protection while adapting to thermal and mechanical changes during operation.
Solution Approach 2:
The patent transforms the static, pre-determined compression thresholds into dynamic parameters that change in real-time based on loudspeaker operating conditions. The system continuously adapts compression ratios, thresholds, and frequency band configurations according to measured impedance and excursion data, making the protection system responsive to thermal heating, mechanical wear, and other time-varying characteristics.
3Reliability
If manual calibration of multiband compressor thresholds is performed, then initial excursion protection is established, but the process is time-consuming and does not account for production variations
Solution Approach 1:
The patent enables the loudspeaker system to automatically calibrate its own compression parameters during initial operation or through a brief measurement routine. The system self-adjusts by measuring its own impedance characteristics and excursion behavior, eliminating the need for manual calibration while accounting for production variations. This self-service approach significantly improves production efficiency without sacrificing protection reliability.
Solution Approach 2:
The patent automates the parameter adjustment process by using measured impedance and excursion data to dynamically determine optimal compression thresholds. Instead of requiring manual calibration, the system automatically changes parameters such as compression ratios, threshold levels, and frequency band definitions based on the specific characteristics of each loudspeaker unit, thereby accommodating production variations while maintaining high productivity.
Data Source
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AI summary
An apparatus and method of excursion protection of a loudspeaker. The method includes attenuating selected bands in a transform domain, controlled by a feedback signal resulting from an excursion transfer function that has been modified according to the real-time operational characteristics of the loudspeaker. In this manner, the system reduces the amount of wideband attenuation needed to address the predicted excursion, resulting in a better listening experience.