Elastomer Micro Speaker Diaphragm for Compact Wide-Band Audio
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional micro speakers face a conflict between being compact and achieving a wide range of frequencies due to the interdependence of membrane and back volume stiffness, resulting in high resonant frequencies that limit bass quality and compactness.
Innovation Solution
A micro speaker design featuring an elastomer membrane with a thickness less than 0.3mm and a Young's modulus below 100MPa, significantly increasing membrane compliance to dominate the resonant frequency, allowing for a minimized back volume and compact size while maintaining wide-band performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional thermoplastic foil membrane is used with deep drawing or stamping, then the membrane can be manufactured with standard processes, but the resonant frequency is high (at least 750Hz) which limits wide-band performance
Solution Approach 1:
The patent changes the material parameter from thermoplastic foil (Young's modulus 1-2GPa) to elastomer material (Young's modulus below 100MPa, preferably 10-50MPa). This parameter change in material stiffness enables the membrane to dominate the resonant frequency determination while maintaining manufacturability through injection molding processes.
2Volume of moving object
If the back volume is reduced to achieve compactness, then the speaker size is minimized, but the resonant frequency increases which degrades wide-band performance
Solution Approach 1:
The patent changes the membrane stiffness parameter by using elastomer material with Young's modulus below 100MPa. This enables the membrane compliance to be at least a factor of 10 higher than back volume compliance, allowing the back volume to be reduced to minimum size while maintaining low resonant frequency through the relationship: resonant frequency is dominated by membrane compliance when membrane compliance >> back volume compliance.
3Strength
If the membrane stiffness is increased to improve structural integrity, then the membrane can support higher frequencies, but the resonant frequency increases which reduces bass quality and wide-band performance
Solution Approach 1:
The patent inverts the conventional approach by making the membrane extremely compliant (Young's modulus below 100MPa) rather than stiff. This inversion enables the membrane to dominate resonant frequency determination in the desired direction (low frequency for wide-band performance) while the back volume structure provides the necessary structural support.
4Manufacturing precision
If the membrane thickness is reduced to increase compliance, then the resonant frequency decreases improving wide-band performance, but the membrane becomes too thin for standard manufacturing processes
Solution Approach 1:
The patent changes both material parameter (to elastomer) and thickness parameter (to less than 0.3mm, preferably 0.05-0.2mm). The elastomer material's low Young's modulus compensates for the reduced thickness, maintaining sufficient compliance while enabling manufacturing through injection molding processes that can reliably produce thin-walled elastomer components.
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
The solution enables a resonant frequency below 300 Hz, achieving improved bass quality and compactness by making the back volume the primary determinant of the resonant frequency, reducing manufacturing variations, and ensuring stability across temperature ranges.
Implementation Method 1
the membrane is an elastomer membrane of a thickness less than 0.3mm and with a Young's modulus below 100MPa
Implementation Method 2
The performance of the speaker is dependent on the resonant frequency. Above the resonant frequency, the output response is relatively flat.
Implementation Method 3
The speaker comprises a membrane attached to a voice coil, which is positioned within a magnetic field defined by a permanent magnet and yoke arrangement
Data Source
Figure 1~2
AI summary
A speaker comprises a permanent magnet (2) and a coil (8) positioned around the permanent magnet (2) and attached to a membrane (10), wherein the membrane comprises an elastomer of thickness less than 0.3mm and with a Young's modulus below 100MPa.