Loudspeaker Equalizer Using Global Transfer Function Gain Limits
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Solution Overview
Problem
Existing methods for equalizing loudspeakers in rooms often result in severe sound quality degradation when listeners move outside the designated listening position, require numerous manual corrections, or introduce high gains at specific frequencies due to room modes, leading to poor sound reproduction across larger areas.
Innovation Solution
A method that measures the listening position transfer function and determines a global transfer function to create an equalizing filter with frequency-dependent upper and lower gain limits, limiting gains to adapt to the room's general acoustic properties, thereby reducing coloration and power consumption while maintaining sound quality across a larger area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single point equalizing approach is used to correct frequency characteristics at the listening position, then sound reproduction quality is improved at that position, but sound quality degrades significantly for listeners outside the listening position
Solution Approach 1:
The patent applies local quality by creating multiple equalizing filters tailored to different spatial zones within the room. Each filter is optimized for specific listening positions, allowing the system to provide accurate frequency correction locally while maintaining overall adaptability across the entire listening area through selective filter application.
Solution Approach 2:
The patent segments the listening area into multiple zones with distinct acoustic characteristics. By dividing the room into different spatial regions and creating separate equalizing filters for each zone, the system maintains precise frequency correction for each segment while collectively covering the entire listening area, thus resolving the contradiction between local precision and global adaptability.
2Adaptability or versatility
If a multi-point equalizing approach is used to average transfer characteristics in multiple positions, then sound reproduction is improved for a larger listening area, but a large number of manual corrections are required
Solution Approach 1:
The patent implements self-service by enabling the system to automatically perform equalizing filter design and selection without requiring skilled operators to manually adjust multiple filters. The system autonomously measures room acoustic characteristics, generates appropriate equalizing filters, and applies them based on detected listening positions, thereby achieving multi-point equalizing coverage while eliminating complex manual corrections.
Solution Approach 2:
The patent utilizes parameter changes by automatically adjusting filter coefficients and selecting appropriate equalizing filters based on measured acoustic parameters at different listening positions. This automated parameter optimization allows the system to adapt to multiple positions and achieve broad area coverage without requiring manual intervention for each position's correction.
3Measurement precision
If equalizing filter gain is increased to compensate for room modes at specific frequencies, then frequency response is corrected at the listening position, but high gains cause power consumption increase and potential distortion
Solution Approach 1:
The patent applies partial action by implementing frequency-dependent gain limits that allow sufficient correction only where necessary to achieve acceptable frequency response, rather than attempting complete compensation at all frequencies. This approach provides adequate frequency correction while avoiding excessive gains that would waste power and potentially cause distortion, thus resolving the contradiction between correction precision and energy efficiency.
Data Source
AI summary
Disclosed is a method for equalizing a first loudspeaker positioned in a room in order to compensate for an influence of the room, the method comprising the steps of 1) measuring a listening position transfer function from electrical input of the first loudspeaker to a sound pressure at a listening position in the room, 2) determining a global transfer function representing a spatial average of sound pressure level in the room generated by the first loudspeaker, 3) determining an upper gain limit as a function of frequency, the upper gain limit being based on an inverse of the global transfer function, 4) determining an equalizing filter based on an inverse of the listening position transfer function, wherein a gain of the equalizing filter is limited to a maximum gain in accordance with the upper gain limit, and 5) equalizing the first loudspeaker according to the equalizing filter.