Electrodynamic Transducer Inner Seal and Waveguide Extension
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Solution Overview
Problem
Electrodynamic acoustic transducers face performance deficiencies at both low and high frequencies due to air leakage between the voice coil and pole piece, leading to noise and distortion issues, with existing solutions only partially addressing these problems.
Innovation Solution
The transducer design incorporates a waveguide extension structure and an inner flexible roll seal made from non-porous material to seal the gap between the voice coil and pole piece, reducing air leakage and providing resistive termination damping to minimize resonances and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a dustcap is used to seal the gap between voice coil and pole piece, then air leakage is reduced and low frequency noise is improved, but high frequency cavity resonances are not eliminated
Solution Approach 1:
The sealing function is divided into two segments: a dustcap for low frequency sealing and an inner flexible roll seal for high frequency sealing. Each segment addresses specific frequency ranges, with the roll seal specifically targeting high frequency cavity resonances that the dustcap cannot eliminate.
Solution Approach 2:
The inner flexible roll seal acts as an intermediary element between the voice coil and pole piece, providing a compliant sealing interface that specifically addresses high frequency acoustic leaks while allowing the dustcap to handle low frequency sealing.
2Object-generated harmful factors
If a waveguide extension structure is used to fill the cavity, then high frequency resonances are reduced, but air leakage through the gap remains unaddressed
Solution Approach 1:
The waveguide extension structure and inner flexible roll seal are merged into a single integrated component that simultaneously performs both functions: filling the cavity to reduce high frequency resonances and sealing the gap to prevent air leakage.
3Loss of energy
If the gap between voice coil and pole piece is sealed, then air leakage is reduced, but the piston area is reduced
Solution Approach 1:
The inner flexible roll seal uses a thin, compliant sealing interface that prevents air leakage while occupying minimal space, thereby preserving the effective piston area of the voice coil.
4Loss of energy
If a rigid seal is used to seal the gap, then air leakage is prevented, but unwanted reflections and resonances increase
Solution Approach 1:
The flexible roll seal provides a compliant sealing interface that absorbs and dampens unwanted reflections and resonances, preventing the rigid reflection issues associated with hard seals.
Solution Approach 2:
The seal material properties are selected to provide appropriate acoustic impedance matching, transforming the seal from a rigid reflector into an absorptive element that reduces reflections while maintaining sealing effectiveness.
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 effectively reduces air leakage, noise, and high-frequency resonances while maintaining efficiency and excursion capabilities, with minimal impact on piston area, moving mass, and efficiency compared to traditional designs.
Implementation Method 1
an inner flexible roll seal made from non-porous material to seal the gap between the voice coil and pole piece, reducing air leakage
Implementation Method 2
providing resistive termination damping to minimize resonances and noise
Implementation Method 3
the coil moves under influence of the Lorentz electromotive force exerted by the magnetic field of the permanent magnet on the charged particles flowing through the voice coil's windings
Data Source
AI summary
An acoustic transducer includes a frame, voice coil movable along a pole, magnetic structure generating magnetic flux in a gap where the voice coil moves, diaphragm attached to the coil, waveguide extension in front of the pole, inner flexible roll seal connecting the waveguide extension to neck area of the diaphragm, and outer seal connecting outer periphery of the diaphragm to the frame. The inner flexible roll seal seals the gap between the voice coil and the pole, isolating the air in front of the diaphragm from the air behind the diaphragm. The inner seal provides damping of unwanted resonances of the diaphragm. Together, the inner seal and the outer seal do not substantially decrease the piston area of the transducer, and do not substantially affect the transducer's movement. In combination, the inner seal and the waveguide extension tend to increase efficiency and decrease audio distortions of the transducer.