Multi-Band Speaker Limiting for Bass Extension and Low Distortion
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Solution Overview
Problem
Conventional single-band limiters in audio systems compromise between bandwidth and maximum sound level, often requiring a trade-off between bass capability and distortion performance, leading to substantial distortion at high output levels.
Innovation Solution
A system and method that utilize multiple filter circuitries, including lowpass, highpass, and allpass filters, along with independent limiter circuitries, to selectively limit and combine audio signals, allowing for independent threshold settings and frequency management to extend bass frequency range while maintaining sound level at maximum output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional single-band limiter applies a limiting gain to all frequencies equally, then the maximum output sound level can be increased, but the distortion performance deteriorates due to the compromise between bandwidth and maximum output sound level
Solution Approach 1:
The patent divides the audio signal into multiple frequency bands using filter circuitries (lowpass, highpass, and bandpass filters). Each frequency band is then processed by independent limiter circuitries with separate threshold settings. This segmentation allows different limiting strategies to be applied to different frequency ranges, enabling the system to maintain higher maximum output sound levels in certain bands while controlling distortion in others, thereby resolving the contradiction between power and distortion.
2Adaptability or versatility
If the cutoff frequency of the high pass filter is increased to retain deeper bass frequencies, then the bass capability is improved, but the operation bandwidth is reduced and much of the bass content is removed
Solution Approach 1:
The patent employs multiple filter circuitries to segment the frequency spectrum into distinct bands. By using independent lowpass, highpass, and bandpass filters, the system can preserve deep bass frequencies in dedicated low-frequency bands while maintaining adequate bandwidth for mid and high frequencies. Each band is processed independently, allowing the system to optimize bass capability without sacrificing overall operational bandwidth.
Solution Approach 2:
The patent extends the frequency response into the sub-bass region (below 20 Hz) by adding dedicated lowpass filter circuitries with cutoff frequencies set to include sub-bass content. This dimensional extension into lower frequencies allows the system to enhance bass capability beyond the conventional audible range while maintaining the necessary bandwidth for full-range audio reproduction through parallel processing paths.
3Object-generated harmful factors
If the limiter is tuned in a very aggressive way to lower the sound level at maximum output, then the distortion performance is improved, but the bass capability and maximum output sound level are reduced
Solution Approach 1:
The patent applies different limiting characteristics to different frequency bands. Low-frequency bands can use more aggressive limiting with lower thresholds to control distortion in the bass region, while mid and high-frequency bands use more conservative limiting with higher thresholds to preserve maximum output sound level and dynamic range. This localized quality control allows the system to achieve good distortion performance in critical bass frequencies without sacrificing overall power and maximum output levels.
Data Source
AI summary
A system is provided for limiting distortion of an audio speaker. The system includes a first lowpass filter circuitry that is configured to receive a system input signal and generate a first lowpass filtered output signal. The system also includes a first limiter circuitry that is configured to limit the first lowpass filtered output signal. Limiting the first low pass filtered output signal includes reducing an amplitude of the first lowpass filtered output signal below a first predetermined threshold value, thereby to generate a first limited output signal. A second lowpass filter circuitry is configured to receive the first limited output signal and to generate a second lowpass filtered output signal.