Active Speaker Band-Split Limiter for Clipping-Free Higher SPL
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Solution Overview
Problem
Conventional limiter systems in active speakers cause undesirable clipping distortion and limit the maximum sound level due to their inability to differentiate between frequency bands, leading to uneven volume adjustments across all frequencies when low-frequency signals exceed the voltage limit.
Innovation Solution
A limiter system comprising a first equalization filter, low-pass filter, first limiter, high-pass filter, second limiter, and a mixer, with a second equalization filter, where signals are divided into low-frequency and high-frequency bands, and limited separately to avoid exceeding the maximum voltage limit, and the second equalization filter adjusts the mixed signal to prevent clipping distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional limiter limits signals at all frequencies below a limiting threshold, then the maximum voltage limit is protected, but the volume of human voices at higher frequencies suddenly drops when low-frequency signals appear
Solution Approach 1:
The audio signal is divided into multiple frequency bands using band-pass filters, with each band having its own independent limiter. This segmentation allows different limiting thresholds to be applied to different frequency ranges, preventing the volume instability that occurs when a single limiter compresses all frequencies uniformly.
Solution Approach 2:
Different limiting thresholds are assigned to different frequency bands according to their specific characteristics. The limiter applies localized control to each frequency band rather than uniform control across the entire spectrum, allowing bass frequencies to be limited at one threshold while preserving volume stability for mid-range human voice frequencies at a different threshold.
2Reliability
If the limiter is set to a lower gain to avoid clipping distortion at crossover frequency, then clipping noise is avoided, but the maximum sound level of the speaker system is reduced
Solution Approach 1:
The frequency spectrum is segmented into multiple bands, each with optimized limiting thresholds. This allows the system to maintain higher overall gain settings because each band can be limited independently at appropriate levels, preventing the need to reduce the global gain to avoid clipping in any single band.
Solution Approach 2:
The limiting threshold parameter is changed from a single uniform value to multiple frequency-dependent values. By adjusting the threshold parameter differently for each frequency band, the system can operate at higher maximum sound levels while still preventing clipping distortion in vulnerable frequency regions.
3Device complexity
If a single limiting threshold is used for all frequencies, then the limiter structure is simple, but signals at different frequencies are equally compressed causing undesirable volume changes
Solution Approach 1:
The audio signal path is segmented into multiple frequency bands, each processed by its own limiter with independent threshold control. This segmentation transforms the simple single-threshold structure into a multi-threshold structure that maintains volume consistency across different frequencies by allowing each band to be limited independently.
Solution Approach 2:
The limiting threshold is made dynamic and frequency-dependent rather than static and uniform. Each frequency band can have its threshold adjusted dynamically based on the signal characteristics in that band, allowing the system to adapt to different musical content while maintaining natural volume relationships between frequencies.
Data Source
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AI summary
The present disclosure provides a limiter system (100) including a first equalization filter (110), a low-pass filter (120), a first limiter (130), a high-pass filter (140), a second limiter (150), and a mixer (160). The limiter system (100) further includes a second equalization filter (170). An audio signal from a signal source first passes through the first equalization filter (110), the signal equalized for the first time is divided into two signals, one signal is processed by the low-pass filter (120) and the first limiter (130), the other signal is processed by the high-pass filter (140) and the second limiter (150), and then the two processed signals enter the mixer (160) to be mixed and outputted. The mixed output signal is subjected to second equalization filtering by the second equalization filter (170) to avoid clipping distortion or to obtain a higher maximum sound level.