Expanded Material Acoustic Diaphragm for Stiffness and Mass Trade-off
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Solution Overview
Problem
Conventional acoustic diaphragms face challenges in achieving the ideal balance of rigidity and low mass, which affects their performance in sound reproduction by requiring high starting force and energy storage.
Innovation Solution
The development of an acoustic diaphragm utilizing an expanded material with more than 55% volume voids, composed of cellulose, synthetic fibers, or glass fibers, often with a skin made from different materials and an adhesive, to enhance stiffness and damping, while maintaining low density and variable thickness for tailored performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the diaphragm mass is reduced to minimize starting force requirements, then the force requirements are reduced, but the rigidity decreases leading to uncontrolled motions
Solution Approach 1:
The diaphragm uses a composite structure combining an expanded low-density core material (providing low mass) with high-density peripheral regions or reinforcement structures (providing rigidity). This composite approach allows the diaphragm to achieve both low overall mass for reduced starting force and sufficient local rigidity to control motion.
Solution Approach 2:
The diaphragm employs non-uniform density distribution where the expanded material provides low density in central regions for lightness, while peripheral regions or specific structural zones maintain higher density for rigidity. This local variation in material properties allows simultaneous optimization of mass and strength.
2Weight of moving object
If the diaphragm mass is reduced to minimize energy storage issues, then energy storage problems are reduced, but the structural integrity and controlled motion capability deteriorate
Solution Approach 1:
The composite structure with expanded core and reinforced periphery or damping materials provides both low mass for reduced energy storage issues and sufficient structural integrity for controlled motion. The high-density regions or damping layers ensure reliable, predictable motion behavior.
Solution Approach 2:
The expanded porous material provides low density while maintaining structural integrity through its cellular structure. The porous architecture allows the diaphragm to remain lightweight yet sufficiently rigid to achieve controlled, reliable motion without excessive energy storage.
3Weight of moving object
If the diaphragm density is reduced to achieve low areal density, then the starting force requirements are minimized, but the bending resistance decreases
Solution Approach 1:
The diaphragm features non-uniform density distribution with low-density expanded material in regions where bending resistance is less critical, and higher-density regions or reinforcement structures where bending resistance is needed. This local quality variation optimizes both areal density and bending resistance.
Solution Approach 2:
The composite construction combines low-density expanded core material with higher-density peripheral regions, skins, or reinforcement layers. This allows the overall areal density to remain low while providing sufficient bending resistance through the strategically placed higher-density components.
Data Source
AI summary
An acoustic diaphragm made at least in part from an expanded material. The expanded material includes one or more of cellulose, synthetic fibers and glass fibers. The expanded material has more than about 55% by volume voids.