Magnetic Negative Spring Loudspeaker for Radial Stability Control
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Solution Overview
Problem
Loudspeakers with magnetic negative springs (MNS) face issues such as radial instability, non-linear force vs displacement curves leading to audible distortions, inner stator magnet segments breaking free, and instability at high altitudes due to decreased air pressure.
Innovation Solution
The design incorporates a magnetic negative spring with specific magnet arrangements for radial stability, a variable air volume system to adjust resonance frequency, and a moveable ferromagnetic plunger to adjust magnetic reluctance, along with an armature centering mechanism and pressure sensors for feedback control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a magnetic negative spring is used to cancel large pressure forces on the sound panel, then the force balance is improved, but radial instability occurs causing the armature to contact stator magnets
Solution Approach 1:
A ferromagnetic centering ring is introduced as an intermediary component between the armature magnets and the stator magnets. This centering ring provides a magnetic path that generates centering forces to counteract radial instability, while allowing the MNS to continue providing pressure force cancellation. The centering ring acts as a mediator that resolves the conflict between force balance and radial stability.
Solution Approach 2:
The magnetic properties are distributed non-uniformly through the use of multiple armature magnets with different polarities arranged around the periphery, and corresponding stator magnets arranged in alternating polarity patterns. This local variation in magnetic polarity creates localized centering forces at different angular positions, which collectively provide overall radial stability while maintaining the global force balance function of the MNS.
2Stability of the object's composition
If permanent magnets are used for the MNS to provide radial stability, then radial stability is improved, but the inner stator magnet segments break free from epoxy bonds
Solution Approach 1:
The ferromagnetic centering ring serves as an intermediary that carries the magnetic flux and provides centering forces without requiring the stator magnet segments to be strongly bonded. The centering ring distributes the magnetic forces more evenly, reducing the peak stresses that cause epoxy bond failure in the stator magnet segments.
3Force
If the MNS provides strong magnetic forces for pressure cancellation, then force balance is improved, but the system becomes unstable at high altitudes due to decreased air pressure
Solution Approach 1:
The system is made dynamically adaptable to changing environmental conditions through the use of electronically controlled electromagnets instead of fixed permanent magnets. The controller adjusts the current through the voice coil and electromagnet windings to maintain optimal magnetic forces despite changes in air pressure at different altitudes. This dynamic adjustment allows the system to maintain both force balance and stability across varying atmospheric conditions.
4Power
If the magnetic field strength is increased to improve force per unit current, then the actuator efficiency is improved, but the radial instability increases causing armature-stator contact
Solution Approach 1:
The ferromagnetic centering ring is positioned within the air gap to provide a localized magnetic path that generates centering forces. This allows the main magnetic field to be optimized for force production while the centering ring's magnetic field specifically addresses radial stability. The centering ring effectively decouples the optimization of force strength from the constraint of radial stability.
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 design enhances radial stability, linearizes the force curve, prevents stator magnet segments from breaking, and maintains stability across varying altitudes by dynamically adjusting resonance frequency and magnetic stiffness.
Implementation Method 1
The magnetic negative spring is operable to provide a first magnetic negative spring force when the sound panel is moving toward the enclosure and a second magnetic negative spring force when the sound panel is moving away from the enclosure. The first magnetic negative spring force is oppositely directed to the first air pressure force. The second magnetic negative spring force is oppositely directed to the second air pressure force.
Implementation Method 2
one pole width of the voice coils 1815a-1815b are always immersed in the magnetic field (which makes the force per unit current input approximately constant at all armature positions)
Implementation Method 3
a moveable ferromagnetic plunger to adjust magnetic reluctance
Implementation Method 4
a variable air volume system to adjust resonance frequency
Implementation Method 5
an actuator operable to convert electrical energy into mechanical energy
Data Source
AI summary
Electroacoustic drivers that can be utilized in loudspeaker systems that utilize drivers having a magnetic negative spring (MNS). The magnets of the MNS can be arranged for radial stability and/or to provide for linear magnetic forces. A variable reluctance device can be used to vary the resonant frequency of electroacoustic driver in response to a feedback signal.