Vehicle Loudspeaker Back-Space Taper for Low-Tone Sensitivity
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Solution Overview
Problem
Existing vehicle-mounted loudspeakers face challenges in increasing output sensitivity for low-tone sounds due to acoustic resistive load limitations, which restrict diaphragm movement and reduce sound pressure applied to the vehicle interior, especially around the Helmholtz resonance frequency.
Innovation Solution
The loudspeaker design includes a diaphragm with a tapered part and a case with a tapered inner wall surface, where the area of the back space between the diaphragm and the case increases gradually towards the duct, reducing resistive load and allowing for a higher Helmholtz resonance frequency without increasing duct opening size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inner volume of the back space is reduced to increase the resonance frequency of the Helmholtz resonator, then the resonance frequency increases, but the counter distance between the inner wall surface and the diaphragm is shortened, increasing resistive load and reducing output sensitivity
Solution Approach 1:
The patent applies curvature by forming the back space with a tapered inner wall surface that gradually increases in cross-sectional area from the diaphragm toward the duct opening. This curved/tapered geometry allows the air to flow more smoothly with reduced turbulence and resistive load, thereby maintaining high output sensitivity even when the overall back space volume is reduced to achieve higher resonance frequency.
2Reliability
If the duct is made thicker and shorter to increase resonance frequency, then the resonance frequency increases, but the opening diameter cannot be increased due to vehicle constraints and foreign matter intrusion concerns
Solution Approach 1:
The patent applies local quality by creating a non-uniform cross-sectional area distribution within the back space through the tapered inner wall surface. The cross-sectional area is smaller near the diaphragm and gradually increases toward the duct opening, optimizing the local flow characteristics in different regions. This allows the duct to maintain a constrained opening diameter while still achieving the desired resonance frequency and minimizing resistive load.
3Reliability
If the case is made smaller to increase resonance frequency, then the resonance frequency increases, but the counter distance is shortened, increasing resistive load and reducing low-tone sound output sensitivity
Solution Approach 1:
The patent applies curvature by forming the back space with a tapered inner wall surface that gradually increases in cross-sectional area from the diaphragm toward the duct opening. This curved/tapered geometry allows the air to flow more smoothly with reduced turbulence and resistive load, thereby maintaining high output sensitivity even when the overall back space volume is reduced to achieve higher resonance frequency.
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 design enhances sound pressure application to the vehicle interior by reducing resistive load, allowing for higher resonance frequencies and improved output sensitivity, particularly in the frequency band used as a woofer.
Implementation Method 1
The case having the duct operates as a Helmholtz resonator. Around the resonance frequency of the Helmholtz resonator, the resonance of air in the duct increases the inner pressure in the case
Implementation Method 2
When a cross-section including a center line of vibration and a center of an opening of the duct is defined as a longitudinal cross-section... an area of a back space... is larger when seen in a transverse cross-section than when seen in the longitudinal cross-section... capable of reducing an acoustic resistive load moving from a back space between an inner wall surface of a case and a diaphragm toward a duct when the diaphragm vibrates
Data Source
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AI summary
A vehicle-mounted loudspeaker capable of reducing a load mass acting on a diaphragm, even with reduction in the volume of a back space of a case, is provided. A case has a flat region and a tapered region on the periphery of the flat region. The centroid of the flat region is set at a position closer to a duct than the center line of vibration of the diaphragm is. The width dimension of the tapered region when seen in a plane is larger at positions apart from the duct and narrower at positions closer to the duct along circumferential loci. As a result, the back space in the case gradually widens from the position apart from the duct toward the duct along the circumferential loci.