Speaker Crossover Optimization With All-Pass Phase Alignment
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Solution Overview
Problem
Modern sound systems face challenges in achieving accurate sound reproduction due to the inability of existing cross-over filters to produce a flat amplitude response across the crossover region, leading to spectral notches and amplitude variations when sound waves from subwoofer and satellite speakers are out of phase, resulting in inefficient sound reproduction.
Innovation Solution
A method that optimizes the crossover frequency by minimizing an objective function measuring magnitude response variation and applies all-pass filtering to reduce incoherence between speakers, using recursive adaptive or constrained optimization algorithms to derive all-pass filters for signal processing circuitry associated with satellite and subwoofer channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional cross-over filters are used to allocate frequency bands to speakers, then frequency domain splitting is achieved, but spectral notches and amplitude variations occur in the crossover region due to out-of-phase sound waves from multiple speakers
Solution Approach 1:
The patent changes the phase parameter of signals in the crossover region using all-pass filters. By applying frequency-dependent phase adjustments through adjustable all-pass filters, the system modifies the phase relationship between signals from different speakers without altering their magnitude responses, thereby eliminating spectral notches caused by out-of-phase cancellation
Solution Approach 2:
The system employs an optimization process that measures the actual frequency response in the crossover region and adjusts the all-pass filter parameters to minimize spectral deviations. This feedback loop continuously optimizes the phase alignment between speakers based on measured performance, reducing harmful spectral notches while maintaining frequency domain splitting
2Adaptability or versatility
If sound waves from multiple speakers at non-coincident positions are combined, then full frequency range coverage is achieved, but incoherent addition creates large variations in magnitude response
Solution Approach 1:
The patent applies phase parameter changes through all-pass filters to align the phase of sound waves from speakers at non-coincident positions. By adjusting the phase of individual speaker signals in the crossover region, the system ensures coherent addition of sound waves, maintaining consistent magnitude response across the full frequency range while preserving the benefits of multiple speaker positions
Data Source
AI summary
A system and method provide at least a single stage optimization process which maximizes the flatness of the net subwoofer and satellite speaker response in and around a cross-over region. A first stage determines an optimal cross-over frequency by minimizing an objective function in a region around the cross-over frequency. Such objective function measures the variation of the magnitude response in the cross-over region. An optional second stage applies all-pass filtering to reduce incoherent addition of signals from different speakers in the cross-over region. The all-pass filters are preferably included in signal processing for the satellite speakers, and provide a frequency dependent phase adjustment to reduce incoherency between the center and left and right speakers and the subwoofer. The all-pass filters are derived using a recursive adaptive algorithm.