Subwoofer Distance Measurement Using Pulse Width Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing home theater systems face challenges in accurately measuring the distance of subwoofers from a listening position due to the band-limited response and built-in low-pass crossover, leading to inaccurate sound optimization.
Innovation Solution
The solution involves using an adjustable factor based on both pulse location and width, derived from empirical data through polynomial curve fitting or lookup tables, to correct for subwoofer crossover settings and characteristics, ensuring accurate distance calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional impulse response peak detection is used to measure subwoofer distance, then the measurement process is simple, but the measurement precision is poor due to band-limited response and crossover settings
Solution Approach 1:
The patent transforms the distance measurement from relying solely on peak detection time to using both peak detection time and impulse width parameters. By incorporating impulse width (measured at specific amplitude thresholds like 0.707 or 0.5 of peak amplitude) into the distance calculation, the system compensates for the distorting effects of band-limited response and crossover networks, thereby improving measurement precision without requiring complex additional hardware
Solution Approach 2:
The patent introduces an intermediary calculation layer that uses empirically derived relationships between impulse width, peak location, and actual distance. By creating a correction model based on measured impulse characteristics, the system mediates between the raw impulse response data and the final distance measurement, eliminating the need for direct peak-only detection while maintaining computational feasibility
2Measurement precision
If subwoofer crossover settings are adjusted to improve distance measurement accuracy, then measurement precision improves, but ease of operation deteriorates as it requires consumer expertise
Solution Approach 1:
The patent enables the measurement system to automatically compensate for crossover settings without requiring user intervention. By measuring the impulse response characteristics directly from the subwoofer's actual output (including its inherent crossover filtering) and using these characteristics to calculate distance, the system makes the subwoofer's own response characteristics serve the measurement process rather than requiring the user to modify those characteristics
Solution Approach 2:
The patent extracts the essential measurement information (peak location and impulse width) directly from the impulse response without requiring separation or modification of the crossover effects. By taking out only the necessary temporal characteristics of the impulse response, the system avoids the need to physically adjust crossover settings while still achieving accurate distance measurement
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 approach significantly increases the accuracy of subwoofer distance measurement, allowing for optimal sound setup without requiring changes to the subwoofer crossover settings or consumer expertise.
Implementation Method 1
a noise source 210 may be used to generate a sound pattern or series of impulses or the like through speaker 220
Data Source
AI summary
The present invention automatically corrects for subwoofer or other speaker crossover settings or other parameters by providing an adjustable factor passed upon not only pulse location, but on pulse width. In FIG. 2, as the low-pass frequency of the subwoofer is decreased, either by the crossover setting or the physical design of the subwoofer, the impulse response is shifted to the right and the width of the impulse increases. By relating the adjustment factor to the width of the impulse, the accuracy of the computed distance is greatly increased. The relation may be found doing a simple polynomial curve fitting to empirical data from several subwoofers at various crossover settings and distances, storing that data, and then measuring pulse location and width of the actual subwoofer during the setup routine, and adjusting the distance (delay) calculations accordingly.