Loudspeaker Controller Impedance Diaphragm Displacement
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Solution Overview
Problem
Existing loudspeaker control methods fail to accurately predict and manage diaphragm displacement under large-amplitude signal conditions due to nonlinear behavior, leading to potential mechanical damage and quality issues.
Innovation Solution
A loudspeaker controller that measures short-term instantaneous impedance variations to estimate diaphragm displacement, using pilot tones or noise signals to derive time-varying impedance information, which is then used to control the loudspeaker's gain and prevent excessive excursion through acoustic signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a linear transfer function is used to predict diaphragm displacement, then the prediction is accurate for small electrical signals, but it becomes inaccurate for large-amplitude signals due to nonlinear behavior
Solution Approach 1:
The patent applies dynamics by making the control system adaptive to changing operating conditions. The controller dynamically adjusts the measurement signal amplitude based on the current input signal level, using a larger measurement signal amplitude for large-amplitude input signals and a smaller measurement signal amplitude for small-amplitude input signals. This dynamic adaptation allows accurate displacement prediction across the full range of signal amplitudes, resolving the contradiction between accuracy for small signals and applicability for large signals.
2Reliability
If mechanical protection is implemented to prevent excessive diaphragm displacement, then the loudspeaker is protected from damage, but the protection may be overly conservative under large-amplitude signal conditions
Solution Approach 1:
The patent implements feedback by continuously measuring the actual diaphragm displacement using impedance measurements and comparing it to the maximum allowable displacement. Based on this feedback, the controller dynamically adjusts the measurement signal amplitude to maintain accurate displacement monitoring across different operating conditions. This feedback mechanism enables reliable mechanical protection without being overly conservative, as the system adapts to the actual operating conditions rather than applying fixed conservative limits.
3Measurement precision
If the amplitude of the measurement signal is increased to improve displacement measurement accuracy under large-amplitude signals, then the measurement robustness improves, but the added signal may interfere with the audio output quality
Solution Approach 1:
The patent applies dynamics by dynamically adjusting the measurement signal amplitude based on the current operating conditions. For large-amplitude input signals, a larger measurement signal amplitude is used to ensure robust displacement measurement. For small-amplitude input signals, a smaller measurement signal amplitude is used to minimize interference with audio output. This dynamic adjustment resolves the contradiction between measurement robustness and audio quality by adapting the measurement signal level to the current signal conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method provides effective mechanical protection for loudspeakers by accurately monitoring and managing diaphragm displacement, extending the device's lifespan and maintaining high-quality audio output under varying signal conditions.
Implementation Method 1
determine, from the measured voltage and current at a frequency corresponding to said measurement signal, time-varying impedance information of the loudspeaker
Implementation Method 2
A loudspeaker is a device having a voicecoil that moves a diaphragm and converts an electrical signal into an acoustic one
Data Source
Figure 1~2
Figure 3
AI summary
A loudspeaker controller (1) for controlling a loudspeaker (2), configured to determine time-varying impedance information of the loudspeaker (2) based on a loudspeaker voltage and a measure of a loudspeaker current and provide for control of the loudspeaker (2) in accordance with said time-varying impedance information.