Loudspeaker Voice Coil Prediction for Nonlinear Distortion Control
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Solution Overview
Problem
Moving coil acoustic transducers experience increased distortion as they amplify sound, leading to size, weight, and cost inefficiencies, particularly in automotive applications, where there is a need for higher output with lower distortion and compatibility with active noise cancellation, engine order cancellation, and echo-cancelation systems.
Innovation Solution
An active sensor-less, low MIPS algorithm and apparatus for non-linear correction in loudspeakers using moving coil transducers, which models and corrects distortion caused by diaphragm suspension and voice coil motor as a function of voice coil position, compatible with automotive hardware, allowing for better control over displacement and excursion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If moving coil acoustic transducers amplify sound at higher levels, then output power increases, but distortion increases
Solution Approach 1:
The system performs preliminary action by predicting the voice coil position and calculating the required pressure compensation before the distortion occurs. The controller uses the predicted position to determine the appropriate compensation signal, preventing distortion rather than correcting it after the fact. This is evident in the claims where the controller generates a compensation signal based on predicted voice coil position to counteract non-linear effects before they manifest in the audio output.
Solution Approach 2:
The system applies dynamics by continuously adapting the compensation signal based on the real-time predicted voice coil position. Rather than using fixed compensation values, the system dynamically adjusts the compensation amount according to the instantaneous position of the voice coil, allowing optimal distortion cancellation across the entire range of motion. This is reflected in the claims where the compensation signal is generated as a function of the predicted voice coil position.
2Object-generated harmful factors
If traditional distortion correction methods are implemented, then distortion is reduced, but device complexity and processing requirements increase
Solution Approach 1:
The system replaces complex mechanical measurement systems with a computational approach. Instead of using physical sensors to measure voice coil position and the associated processing complexity, the system uses a predictive model that calculates position based on electrical parameters and known transducer characteristics. This substitution of mechanical measurement with computational prediction reduces device complexity while maintaining distortion correction effectiveness, as described in the claims where position is predicted rather than directly measured.
Solution Approach 2:
The system applies self-service by using the transducer's own electrical characteristics and control signals to determine its mechanical state. The controller utilizes existing electrical parameters (current, voltage) and the known relationship between electrical input and mechanical output to predict position without requiring external sensors or complex measurement systems. This self-service approach reduces system complexity by making the transducer monitor and correct its own distortion using its inherent characteristics.
3Measurement precision
If voice coil position is directly measured using sensors, then position accuracy improves, but system cost and complexity increase
Solution Approach 1:
The system introduces an intermediary computational model that translates easily measurable electrical parameters into accurate position information. Rather than directly measuring position with complex sensors, the system uses the electrical control signals and known transducer characteristics as intermediaries to infer position accurately. This intermediary approach maintains measurement precision while avoiding the complexity of direct position sensing, as the controller calculates position from electrical parameters through a predictive relationship.
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
The solution provides improved size, weight, and cost efficiency, enabling more output while enhancing performance in active noise cancellation and echo-cancelation systems by effectively addressing non-linear distortion in moving coil transducers.
Implementation Method 1
moving coil acoustic transducers experience increased distortion as they amplify sound
Implementation Method 2
distortion caused by diaphragm suspension and voice coil motor as a function of voice coil position
Data Source
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AI summary
In at least one embodiment, an audio amplifier system including a memory and an audio amplifier is provided. The audio amplifier includes the memory and is programmed to receive an audio input signal and to generate a target current signal based on the audio input signal. The audio amplifier is further configured to generate a first predicted position of a voice coil of a loudspeaker and to generate a first corrected current signal based on the target current signal and on the first predicted position of the voice coil. The audio amplifier is further configured to determine a pressure within a loudspeaker enclosure based at least on the first predicted position of the voice coil and determine a position of a passive radiator based at least on the pressure within the loudspeaker enclosure. The audio amplifier is further configured to generate a second predicted position of the voice coil.