Low-Halogen PPS Acoustic Membrane for Loudspeaker Distortion
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Solution Overview
Problem
Commercially available polyphenylene sulfide (PPS) films used in loudspeaker membranes have high halogen content, leading to unsatisfactory acoustic distortions and increased temperature loads due to design constraints, which compromise stiffness, damping, and sound quality in micro-loudspeakers.
Innovation Solution
A multi-layer composite membrane is developed using PPS films with a halogen content of no more than 550 ppm, combined with damping layers such as pressure-sensitive adhesives, to maintain high flexural rigidity, low density, and internal damping while reducing acoustic distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If commercially available PPS films with high halogen content are used in loudspeaker membranes, then the membranes achieve high flexural rigidity and low density, but the acoustic distortions increase and sound quality deteriorates
Solution Approach 1:
The patent applies parameter changes by controlling the halogen content of PPS film to not more than 550 ppm, which fundamentally alters the material composition parameter. This parameter change resolves the contradiction by maintaining the structural integrity (flexural rigidity) of PPS while eliminating the harmful acoustic distortions caused by excessive halogen content, thereby improving sound quality without sacrificing mechanical strength
Solution Approach 2:
The patent employs composite materials by creating multi-layer structures that combine low-halogen PPS films with other materials. This composite approach allows the membrane to achieve both high flexural rigidity from the PPS layers and reduced acoustic distortions through the synergistic combination with complementary materials that do not exhibit the same harmful acoustic properties
2Volume of moving object
If micro-loudspeakers are designed to be smaller and flatter to meet device requirements, then the device integration improves, but the temperature load on the membrane increases
Solution Approach 1:
The patent applies parameter changes by selecting PPS films with controlled halogen content (≤550 ppm), which alters the thermal and acoustic properties of the membrane. This parameter change enables the membrane to withstand increased temperature loads in compact designs while maintaining acoustic performance, as the optimized material composition provides better thermal stability and resistance to thermal degradation
3Strength
If the membrane stiffness is increased to generate high sound pressure and cover wide frequency range, then the acoustic output improves, but the damping decreases and frequency response becomes less smooth
Solution Approach 1:
The patent resolves this contradiction by using composite materials in multi-layer constructions. The low-halogen PPS layers provide the necessary stiffness for high sound pressure output and wide frequency coverage, while the combination with other materials in the composite structure introduces effective damping mechanisms. This composite approach allows simultaneous optimization of both stiffness and damping properties that cannot be achieved with single materials
Data Source
AI summary
The invention relates to a multi-layer composite for use as a membrane for electroacoustic transducers, comprising at least one first and one second outer layer (cover layer ), at least one of the cover layers (first cover layer) being made from a polypropylene sulfide-plastic, characterized such that the halogen content of the polyphenylene sulfide plastic (PPS-plastic ) does not exceed 550 ppm.