Subwoofer Crossover Control for Sound Localization Stability
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Solution Overview
Problem
In home theater systems, the increased volume of subwoofers leads to mislocalization of sound and degradation of sound quality due to differences in reproducing abilities between subwoofers and speakers, as existing methods fail to maintain a balance of sound volume beyond the crossover frequency.
Innovation Solution
A signal processing device and method that adjusts the output level and cut-off frequency of the subwoofer to maintain its output at the crossover frequency, shifting the cut-off frequency to the low-pitched or high-pitched sound side and changing the filter order in response to changes in sound volume, ensuring balanced sound distribution across frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the sound volume of the subwoofer is increased to emphasize low-pitched sounds, then the low-pitched sound reproduction is improved, but the localization of sounds is moved to the subwoofer side or a feeling of localization is lacking
Solution Approach 1:
The patent dynamically adjusts the cut-off frequency of the low-pass filter applied to the subwoofer signal based on the subwoofer's output level. When the subwoofer volume is increased, the cut-off frequency is shifted to a lower value, preventing the subwoofer from emitting excessive mid-pitched sounds that would cause localization issues. This parameter change resolves the contradiction by allowing volume enhancement while maintaining proper frequency separation.
Solution Approach 2:
The system implements dynamic control where the cut-off frequency is not fixed but varies according to the subwoofer's output level. This dynamic adjustment ensures that as the subwoofer volume changes, the frequency boundary between subwoofer and speaker remains optimal, preventing localization degradation while allowing flexible volume control.
2Power
If the sound volume of the subwoofer is increased to emphasize low-pitched sounds, then the low-pitched sound reproduction is improved, but the sound quality is degraded due to loss of balance in the band exceeding the crossover frequency
Solution Approach 1:
The patent changes the cut-off frequency parameter of the low-pass filter in response to subwoofer output level changes. When subwoofer volume is increased, the cut-off frequency is lowered to prevent the subwoofer from emitting mid-pitched sounds that would unbalance the sound field. This maintains sound quality by ensuring proper frequency distribution across the audio spectrum.
Solution Approach 2:
The system employs feedback control where the subwoofer's output level is monitored and used to adjust the cut-off frequency accordingly. This closed-loop control ensures that the frequency balance is maintained dynamically, preventing sound quality degradation that would result from unbalanced frequency emission.
3Measurement precision
If the cut-off frequency is shifted to maintain subwoofer output level, then the localization feeling is preserved, but the filter characteristics must be dynamically adjusted increasing system complexity
Solution Approach 1:
The patent implements a dynamic filter control system where the cut-off frequency is automatically adjusted based on subwoofer output levels. While this increases control system complexity, it enables the system to maintain optimal localization characteristics across different volume levels. The dynamic nature of the control allows a single system to adapt to various operating conditions.
Data Source
AI summary
A signal processing device for supplying sound signals to a first speaker for emitting a sound on a low-pitched sound side and a second speaker for emitting a sound on a high-pitched sound side higher than the low-pitched sound side, includes a control portion that controls a characteristic of the sound signal supplied to the first speaker so that an output level of the first speaker is maintained at a crossover frequency between the first speaker and the second speaker, when an output level of the sound signal supplied to the first speaker is changed.