Dual Magnetic Gap Speaker Control for Long Stroke Output

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Solution Overview

Problem

Existing speakers face challenges in enlarging stroke width without increasing winding width, which leads to reduced driving force, increased power consumption, and weight, making it difficult to effectively control drive and maintain output sound pressure.

Innovation Solution

A speaker system with multiple voice coils positioned within different magnetic gaps, each with opposite magnetic flux directions, and a displacement detector to control drive polarity based on coil position, allowing selective application of voice coils within these gaps to enhance stroke width and control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If the winding width of the voice coil is increased to enlarge the stroke width, then the stroke width is improved, but the weight of the vibration system increases and the driving force becomes smaller when the winding width exceeds the magnetic gap width

Engineering Contradiction:
Improvestroke widthVSAvoidweight of vibration system
Core Design Contradiction:
Length of moving objectVSWeight of moving object

Solution Approach 1:

The voice coil is divided into multiple segments (first voice coil and second voice coil) positioned at different locations. Each segment has a relatively small winding width, but together they enable a larger effective stroke width by being selectively activated based on displacement detector feedback, avoiding the need for a single large-width coil that would increase weight.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The system dynamically switches between different voice coil segments based on the real-time position detected by the displacement detector. This dynamic activation allows the stroke width to be effectively enlarged without permanently increasing the winding width of individual coils, thereby avoiding unnecessary weight increase while maintaining adequate driving force.

Inventive Principle:
Principle #15Dynamics

2Length of moving object

If the winding width of the voice coil is increased to enlarge the stroke width, then the stroke width is improved, but the driving force acting on the voice coil becomes smaller when the winding width is larger than the width of the magnetic gap

Engineering Contradiction:
Improvestroke widthVSAvoiddriving force
Core Design Contradiction:
Length of moving objectVSForce

Solution Approach 1:

The voice coil is divided into multiple segments (first voice coil and second voice coil) positioned at different locations. Each segment has a relatively small winding width, but together they enable a larger effective stroke width by being selectively activated based on displacement detector feedback, avoiding the need for a single large-width coil that would increase weight.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The system dynamically switches between different voice coil segments based on the real-time position detected by the displacement detector. This dynamic activation allows the stroke width to be effectively enlarged without permanently increasing the winding width of individual coils, thereby avoiding unnecessary weight increase while maintaining adequate driving force.

Inventive Principle:
Principle #15Dynamics

3Force

If the input gain of the voice coil is increased to increase the driving force, then the driving force is improved, but the power consumption increases

Engineering Contradiction:
Improvedriving forceVSAvoidpower consumption
Core Design Contradiction:
ForceVSUse of energy by moving object

Solution Approach 1:

The system dynamically switches between different voice coil segments based on the real-time position detected by the displacement detector. This dynamic activation allows the stroke width to be effectively enlarged without permanently increasing the winding width of individual coils, thereby avoiding unnecessary weight increase while maintaining adequate driving force.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

Different voice coil segments are activated based on the local position of the vibration system. Only the necessary segments are driven at any given time, optimizing the distribution of power consumption and avoiding unnecessary energy expenditure on segments that are not currently contributing to the stroke.

Inventive Principle:
Principle #3Local quality

4Length of moving object

If a single voice coil with large winding width is used to enlarge stroke width, then the stroke width is improved, but the system becomes uncontrollable when the voice coil is displaced outside the magnetic gap

Engineering Contradiction:
Improvestroke widthVSAvoidcontrollability
Core Design Contradiction:
Length of moving objectVSReliability

Solution Approach 1:

The voice coil is divided into multiple segments (first voice coil and second voice coil) positioned at different locations. Each segment has a relatively small winding width, but together they enable a larger effective stroke width by being selectively activated based on displacement detector feedback, avoiding the need for a single large-width coil that would increase weight.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The displacement detector provides real-time feedback on the position of the vibration system, enabling the control unit to dynamically switch between different voice coil segments. This feedback mechanism ensures that the appropriate segments are always activated, maintaining controllability and reliability even as the stroke width is effectively enlarged.

Inventive Principle:
Principle #23Feedback

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 system effectively enlarges stroke width while minimizing winding width, maintaining driving force and reducing power consumption, without generating asymmetric distortion, and ensuring consistent sound output.

Implementation Method 1

the first magnetic gap is configured to propagate magnetic flux in one of radial directions of the speaker, the second magnetic gap is configured to propagate magnetic flux in another of the radial directions of the speaker

Methodology Applied
Scientific EffectElectromagnetic force: Lorentz Force

Data Source

PatentEP4694202A1Acoustic system
Publication Date: 2026.02.11 ALPS ALPINE CO LTD
  • EP4694202A1 patent drawingFigure 1
  • EP4694202A1 patent drawingFigure 2A
  • EP4694202A1 patent drawingFigure 2B

AI summary

An acoustic system provided with a speaker includes a displacement detector, and a drive unit, wherein the speaker includes a first magnetic gap, a second magnetic gap, and voice coils, wherein the first magnetic gap propagates magnetic flux in one of radial directions of the speaker, the second magnetic gap propagates magnetic flux in another of the radial directions of the speaker, a space between the first magnetic gap and the second magnetic gap in the axial direction is larger than a winding width of each of the voice coils, the vibration system vibrates between a position where at least a portion of the voice coils is positioned within the first magnetic gap and a position where at least a portion of the voice coils is positioned within the second magnetic gap, and the drive unit drives each of the voice coils using the audio signal as a drive signal.