Multiband Loudspeaker Excursion Control Without Bass Pumping
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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 rely on pre-determined settings and static models rather than adaptive responses to changing conditions.
Innovation Solution
A system utilizing a feedback signal to perform compression on selected bands in a transform domain, incorporating a multiband compressor controlled by an excursion transfer function estimated from real-time voltage and current information, which generates gains to attenuate predicted excursion and adapt to changing loudspeaker conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wideband limiting is applied 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 signal into multiple frequency bands (e.g., low, mid, high) and applies independent compression thresholds and ratios to each band. This segmentation allows selective attenuation of excursion-causing frequencies while preserving other frequency ranges, avoiding the uniform attenuation problems of wideband limiting.
Solution Approach 2:
Different compression parameters (thresholds, ratios, attack, release) are applied to different frequency bands based on their specific characteristics and contribution to excursion. Low frequencies may use higher ratios while high frequencies use lower ratios, creating localized optimization for each band's excursion contribution.
2Device complexity
If pre-determined compression settings are used, then system complexity is reduced, but adaptability to real-time loudspeaker characteristics is lost
Solution Approach 1:
The system continuously monitors loudspeaker impedance and excursion characteristics, using this feedback to dynamically adjust compression thresholds and ratios. The impedance measurements provide real-time information about the loudspeaker's state, enabling adaptive parameter adjustment without requiring complex manual calibration.
Solution Approach 2:
Compression parameters are made dynamic rather than static, allowing thresholds and ratios to change in real-time based on loudspeaker conditions. This includes adjusting parameters based on temperature, power level, and impedance variations as the loudspeaker operates.
3Manufacturing precision
If multiband compression with explicit calibration is implemented, then excursion limiting precision is improved, but calibration complexity and time are increased
Solution Approach 1:
The system performs self-calibration by automatically measuring its own impedance characteristics and using this information to set appropriate compression parameters. The loudspeaker system calibrates itself during normal operation without requiring external equipment or manual intervention, achieving precision automatically.
Solution Approach 2:
The system performs preliminary impedance measurements and parameter adjustments during initialization or low-power states before full operation begins. This preliminary calibration prepares the system for optimal excursion control without interrupting normal operation or requiring separate calibration sessions.
Data Source
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.