Speaker Magnetic Stiffness Control for Low-Frequency Output
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Solution Overview
Problem
Audio transducers, particularly speakers in compact electronic devices, face challenges in generating low-frequency sounds due to increased stiffness caused by trapped air in the back volume, which limits membrane movement.
Innovation Solution
Implementing magnetic structures on, near, or within the voice coil of a speaker to interact with a permanent magnet, forming bi-stable or tri-stable systems that provide negative stiffness to counteract the stiffness generated by trapped air, thereby reducing the overall stiffness of the membrane suspension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the back volume is reduced in compact electronic devices, then the device size is reduced, but the stiffness of the membrane suspension increases, limiting low-frequency sound generation
Solution Approach 1:
The patent replaces the mechanical air spring system with a magnetic field-based stiffness control system. By using magnetic structures and permanent magnets to generate magnetic forces, the system substitutes the mechanical compression of trapped air with a controllable magnetic field that provides the necessary restoring force while allowing for reduced back volume.
Solution Approach 2:
The patent changes the physical parameters of the suspension system by introducing magnetic structures with specific magnetic moments and using permanent magnets with controlled field strengths. This allows the stiffness parameter to be adjusted independently of the back volume, enabling low-frequency sound generation even in compact enclosures.
2Productivity
If magnetic structures are added to reduce stiffness, then low-frequency sound generation is improved, but the device complexity increases
Solution Approach 1:
The patent merges the stiffness reduction function with the existing voice coil structure by forming magnetic structures directly on or near the voice coil. This integration eliminates the need for separate stiffness control mechanisms, reducing overall device complexity while achieving the desired low-frequency sound generation capability.
Solution Approach 2:
The magnetic structures serve multiple functions: they provide the restoring force for membrane suspension, enable stiffness control for low-frequency response, and can be integrated with the voice coil assembly. This multi-functionality reduces the need for additional components, thereby limiting the increase in device complexity.
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 magnetic structures effectively reduce the stiffness of the speaker membrane, allowing for improved generation of low-frequency sounds without increasing power consumption or requiring additional centering operations.
Implementation Method 1
magnetic structures on, near, or within the voice coil of a speaker to interact with a permanent magnet
Implementation Method 2
forming bi-stable or tri-stable systems that provide negative stiffness to counteract the stiffness generated by trapped air
Implementation Method 3
providing a current through a voice coil that includes a first plurality of windings formed from a non-magnetic material and a second plurality of windings formed from a magnetic material; wherein the current generates a magnetic field that interacts with a fixed magnet
Data Source
AI summary
Aspects of the subject technology relate to stiffness reduction for audio transducers, such as speakers. Stiffness reduction can be provided using one or more magnetic structures configured to move with a voice coil and/or a diaphragm of the speaker, and assist in the motion of the voice coil and/or diaphragm via magnetic interaction with one or more magnets of the speaker. In one or more implementations, the one or more magnetic structures may form a tri-stable system with the one or more magnets.