Loudspeaker Voice Coil Feedback for Nonlinear Distortion Control
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Solution Overview
Problem
Moving coil acoustic transducers experience increased distortion with higher acoustic output, leading to undesirable size, weight, cost, and inefficiency, particularly in automotive applications, where there is a need for lower distortion and higher output systems capable of active noise cancellation, engine order cancellation, and echo-cancellation.
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 and requiring low processing requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If higher acoustic output is achieved in moving coil transducers, then power and sound output increase, but distortion increases and efficiency decreases
Solution Approach 1:
The system uses a feedback mechanism where the audio amplifier predicts voice coil position based on corrected current signals, calculates expected pressure and passive radiator position, then generates a second predicted position that feeds back to refine the corrected current signal, creating a closed-loop control system that actively compensates for non-linearities
Solution Approach 2:
The system performs preliminary correction by generating a first corrected current signal based on predicted voice coil position before the actual distortion occurs, and further refines this with a second predicted position calculation, proactively compensating for non-linear behavior rather than reacting to it
2Power
If higher acoustic output is achieved in moving coil transducers, then sound output increases, but device size and weight increase
Solution Approach 1:
The system changes the operational parameters of the transducer by dynamically adjusting the current signal based on predicted position and non-linear behavior, allowing a smaller transducer to achieve higher effective output through optimized electrical control rather than physical size increases
3Power
If higher acoustic output is achieved in moving coil transducers, then sound output increases, but manufacturing cost increases
Solution Approach 1:
The invention achieves higher output through parameter optimization via software-based non-linear correction rather than through more expensive hardware components, allowing standard transducers to perform at higher levels through intelligent signal processing
4Power
If higher acoustic output is achieved in moving coil transducers, then sound output increases, but energy efficiency decreases
Solution Approach 1:
The feedback mechanism continuously monitors predicted voice coil position and refines the current signal accordingly, ensuring that electrical energy is converted to acoustic energy with maximum efficiency by compensating for non-linear losses in real-time
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 better control over transducer displacement and excursion, enabling more output while improving the performance of acoustic algorithms and reducing size, weight, and cost, with enhanced stability and adaptability, suitable for automotive applications.
Implementation Method 1
voice coil of a loudspeaker
Implementation Method 2
determine a pressure within a loudspeaker enclosure based at least on the first predicted position of the voice coil
Implementation Method 3
determine a position of a passive radiator based at least on the pressure within the loudspeaker enclosure
Data Source
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.