Loudspeaker Motor Assembly Conducting Elements Linearization
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Solution Overview
Problem
Electrodynamic loudspeakers face nonlinear distortion issues due to the position-dependent force factor and voice coil inductance, which affect sound quality, especially at low signal levels and high frequencies.
Innovation Solution
Incorporating a plurality of non-magnetic conducting elements such as aluminum and copper frames, rings, and caps within the motor assembly to linearize the force factor and voice coil inductance, minimizing their dependence on displacement and current, thereby reducing nonlinear distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional voice coil and magnet assembly is used, then the loudspeaker can produce sound, but nonlinear distortion occurs due to position-dependent force factor and inductance
Solution Approach 1:
A conducting element is introduced as an intermediary component between the voice coil and the magnetic field. This conducting element generates an opposing magnetic flux that compensates for the nonlinear variations in the main magnetic flux, thereby linearizing the force factor and inductance characteristics without requiring changes to the fundamental voice coil or magnet assembly structure
Solution Approach 2:
The invention changes the magnetic flux parameter by introducing a conducting element that modifies the total magnetic flux experienced by the voice coil. By carefully designing the conducting element's geometry and position, the opposing flux is tuned to counteract the nonlinear flux variations, transforming the nonlinear Bl(x) characteristic into a linear one
2Productivity
If voice coil moves in magnetic field, then acoustic signals are produced, but inductance varies with position and current causing distortion
Solution Approach 1:
The conducting element serves as a mediator that stabilizes the inductance by generating an opposing flux that compensates for position-dependent and current-dependent variations. This allows the voice coil to move freely for acoustic output while the inductance remains stable
Solution Approach 2:
The conducting element creates a preliminary opposing magnetic flux that anticipates and counteracts the inductance variations before they affect the acoustic output. This pre-compensation approach maintains inductance stability throughout the voice coil's motion range
3Force
If steel parts surround voice coil, then magnetic field is concentrated, but saturation occurs reducing inductance
Solution Approach 1:
The conducting element is positioned to interact with the magnetic field in the region where saturation occurs. It generates an opposing flux that prevents the steel parts from becoming saturated, thereby maintaining consistent inductance while preserving the magnetic force needed for acoustic output
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 achieves significant linearization of voice coil inductance and force factor, minimizing distortion and impedance variations, leading to improved sound quality and reduced high-frequency attenuation.
Implementation Method 1
the voice coil impedance also incorporates magnetic losses and eddy currents
Implementation Method 2
The alternating current generated in the 'secondary' turn produces an alternating current. This current generates an alternating magnetic flux opposite in sign to the flux generated by the voice coil
Implementation Method 3
An alternating current corresponding to electrical signals conveying audio signals interacts with the constant magnetic field. This interaction results in the Laplace force F, expressed as a product of the magnetic flux density B, the overall length of the voice coil's turns linked to the magnetic flux l, and the value of the electrical current running through the voice coil i, F=Bli
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A loudspeaker includes a motor assembly including a magnet having a first face and a second face, a back plate abutting the magnet first face, a pole piece centrally disposed with respect to the back plate and extending beyond the magnet second face, and a top plate concentrically disposed with respect to the pole piece and extending beyond the magnet second face. A non-magnetic conducting frame is attached to the top plate, a non-magnetic conducting cap is disposed within the motor assembly and encircling the pole piece, a first non-magnetic conducting ring is disposed within the motor assembly and encircling the pole piece, and at least one second non-magnetic conducting ring is disposed within the motor assembly and abutting the back plate.