Multi-Coil Loudspeaker Driver With Delayed Digital Coil Signals
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Solution Overview
Problem
Existing loudspeaker systems in portable devices face challenges in producing high volume audio outputs without increasing physical volume or requiring a boosted power supply, and multi-coil loudspeakers often require complex signal encoding and protection systems.
Innovation Solution
A system that uses a modulator and clock-controlled delay elements to generate delayed digital signals for multiple coils, forming a Finite Impulse Response (FIR) filter arrangement, which enhances audio output without needing increased power and simplifies signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a boosted power supply is used to drive a relatively large loudspeaker, then high volume audio output is achieved, but the physical volume occupied increases and sensitivity decreases
Solution Approach 1:
The audio signal is segmented into multiple frequency bands using a pulse density modulator and digital filtering, with each band driving a separate coil. This allows a single loudspeaker to achieve high volume output through coordinated operation of multiple coils rather than relying on a single large driver, thus avoiding the need for increased physical volume or boosted power supply.
2Power
If two loudspeakers are mounted in a back to back configuration, then loudness of audio output increases, but the physical volume occupied doubles and resistance is presented in parallel
Solution Approach 1:
Multiple coils are merged within a single loudspeaker housing, sharing common magnetic circuit and suspension structure. The coils are driven by frequency-separated signals that combine to produce high volume output, achieving the loudness benefit of multiple speakers without the doubled physical volume or parallel resistance configuration.
3Power
If a loudspeaker includes a plurality of different coils responsive to different frequency bands, then high volume audio output is achieved, but complex signal encoding and filtering are required
Solution Approach 1:
A pulse density modulator converts the audio signal into a high-frequency pulse train, which is then filtered into multiple frequency bands. This periodic modulation approach simplifies the filtering requirements compared to traditional multi-band encoding, as the high-frequency carrier allows for sharper, more selective filters and reduces inter-band interference.
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 solution increases loudness of audio output from a single loudspeaker without the need for a boosted power supply, reduces physical volume, and improves signal quality by filtering out-of-band signals and jitter.
Implementation Method 1
a modulator for outputting a digital output signal representative of a received analogue input signal
Implementation Method 2
a clock controlled delay element for applying a delay to the digital output signal to generate a first delayed signal
Implementation Method 3
improves signal quality by filtering out-of-band signals and jitter
Data Source
AI summary
A system for driving a transducer having a plurality of coils, the system comprising: a modulator for outputting a digital output signal representative of a received analogue input signal at a modulator output; a clock controlled delay element for applying a delay to the digital output signal to generate a first delayed signal at a delay element output; wherein the modulator output is couplable to a first coil of the plurality of the coils of the transducer and the delay element output is couplable to a second coil of the plurality of coils of the transducer.