Active Speaker Limiter with Split-Band Clipping Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional limiter systems in active speakers cause undesirable clipping distortion and limit the maximum sound level due to uniform limiting thresholds across all frequencies, especially when dynamic broadband signals with high bass amplitudes are encountered, leading to sudden volume changes in human voices.
Innovation Solution
A limiter system comprising a first equalization filter, low-pass filter, first limiter, high-pass filter, second limiter, and mixer, with a second equalization filter, where signals are divided into low-frequency and high-frequency bands, allowing different limiting thresholds for each band to prevent clipping distortion and increase the maximum sound level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional limiter limits signals at all frequencies below a limiting threshold, then the maximum output voltage is limited to a specific level, but signals at all frequencies are equally compressed causing sudden volume changes in human voices when low-frequency signals appear
Solution Approach 1:
The patent divides the audio signal into multiple frequency bands using bandpass filters, with each band having its own independent limiter. This segmentation allows different limiting thresholds to be applied to different frequency ranges, preventing the uniform compression that causes sudden volume changes in human voices while still protecting against clipping distortion in each band.
Solution Approach 2:
The patent applies different limiting characteristics to different frequency bands. Specifically, the voice frequency band (typically 80-1000Hz) uses a higher limiting threshold to preserve natural volume variations, while other bands use lower thresholds to prevent clipping. This local differentiation of limiting quality maintains sound quality stability while avoiding distortion.
2Reliability
If a conventional limiter is set to a lower gain to avoid clipping noise at crossover frequencies, then clipping distortion is avoided, but the maximum sound level of the speaker system is reduced
Solution Approach 1:
The patent segments the frequency spectrum into multiple bands, allowing the limiter to operate at different gain levels in different bands. At crossover frequencies where clipping is problematic, the limiter uses lower gain to avoid distortion. In frequency bands away from crossover points, the limiter can operate at higher gain to maintain maximum sound level, thus resolving the contradiction between avoiding clipping and maintaining power output.
Solution Approach 2:
The patent implements dynamic limiting thresholds that adapt to the input signal characteristics. When the signal approaches clipping levels at crossover frequencies, the limiting threshold dynamically adjusts to prevent distortion. When the signal is well below clipping levels, the threshold allows higher gain operation, maintaining maximum sound level. This dynamic adjustment resolves the fixed gain limitation of conventional limiters.
Data Source
AI summary
The present disclosure provides a limiter system. The limiter system includes a first equalization filter, a low-pass filter, a first limiter, a high-pass filter, a second limiter, and a mixer. The limiter system provided by the present disclosure further includes a second equalization filter. An audio signal from a signal source first passes through the first equalization filter, the signal equalized for the first time is divided into two signals, one signal is processed by the low-pass filter and the first limiter, the other signal is processed by the high-pass filter and the second limiter, and then the two processed signals enter the mixer to be mixed and outputted. The mixed output signal is subjected to second equalization filtering by the second equalization filter to avoid clipping distortion or to obtain a higher maximum sound level.