Loudspeaker Module Passive Radiator Low-Frequency Boost
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Solution Overview
Problem
Conventional loudspeaker modules in portable devices face challenges in achieving high efficiency and extended low-frequency response due to the fundamental theoretical limits of small enclosures, making it difficult to effectively radiate sound to both the outside and inside spaces.
Innovation Solution
The design includes a loudspeaker module with a first and second front cavity, a rear cavity, and a passive radiator that radiates low-frequency sound to both the outside and inside spaces through strategically placed output ports and channels, utilizing vibratable diaphragms and acoustical resonators to enhance sound radiation and reduce mechanical displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the back cavity of the loudspeaker module is sealed to prevent sound radiation to the interior space, then sound isolation is improved, but low-frequency response and efficiency deteriorate due to fundamental theoretical limits of small enclosures
Solution Approach 1:
The loudspeaker module is divided into separate functional cavities: a first front cavity for the transducer, a second front cavity for the passive radiator, and a rear cavity. This segmentation allows independent optimization of each cavity's function, enabling the passive radiator to radiate low-frequency sound through the second front cavity to the inside space while the transducer operates in the first front cavity with controlled sound radiation.
Solution Approach 2:
The second front cavity serves multiple functions: it acts as a sealed enclosure for the passive radiator, provides a radiation path for low-frequency sound to the inside space of the portable device, and enables the passive radiator to function as both a low-frequency driver and a sound isolation element. This multi-functionality resolves the contradiction between sound isolation and low-frequency response.
2Volume of moving object
If the enclosure size is reduced for portable devices, then device compactness is improved, but low-frequency sound radiation capability deteriorates due to fundamental theoretical limits
Solution Approach 1:
The passive radiator is designed as a vibratable diaphragm that resonates at low frequencies. By utilizing mechanical vibration and resonance of the passive radiator diaphragm, the system can generate effective low-frequency sound radiation from a compact enclosure, overcoming the theoretical limits that would otherwise prevent low-frequency radiation from small volumes.
Solution Approach 2:
The system uses acoustic pressure waves and air movement through the second front cavity to enable low-frequency sound radiation. The passive radiator diaphragm moves in response to pressure changes from the transducer, creating acoustic output without requiring a large enclosure volume, thus resolving the contradiction between compact size and low-frequency radiation capability.
3Productivity
If a passive radiator is added to radiate low-frequency sound, then low-frequency output is improved, but device complexity increases
Solution Approach 1:
The passive radiator is integrated into the existing loudspeaker module structure, sharing the rear cavity and mounting structure with the transducer. The second front cavity is incorporated into the same housing as the first front cavity, allowing both the transducer and passive radiator to operate within a unified enclosure. This merging approach minimizes the increase in device complexity while achieving improved low-frequency output.
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 configuration significantly increases low-frequency output and reduces displacement, achieving a larger acoustical output compared to conventional sealed modules, while maintaining a compact design and minimizing high-frequency modulation distortion.
Implementation Method 1
the first passive radiator is capable of radiating low-frequency sound to the outside of the enclosure or the inside space of the enclosure via the second front cavity
Implementation Method 2
a first passive radiator disposed between the second front cavity and the rear cavity
Data Source
AI summary
An electronic device includes an enclosure defining a chamber and a first output port communicating the chamber with outside of the enclosure; a loudspeaker module disposed within the chamber. The loudspeaker module includes a first front cavity in communication with the first output port, a second front cavity acoustically connected with an inside space of the enclosure, a rear cavity, a transducer disposed between the first front cavity and the rear cavity, and a first passive radiator disposed between the second front cavity and the rear cavity. The passive radiator is capable of radiating low-frequency sound to the inside space of the enclosure via the second front cavity and an inside port or a second passive radiator. Then, the low-frequency sound re-radiates through surfaces of the enclosure and possible leaks in the enclosure to the outside environment. The low-frequency output is boosted.