Dual Voice-Coil Loudspeaker Drive for Displacement Control

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Solution Overview

Problem

Existing loudspeaker designs face challenges in maintaining drive force while minimizing power consumption and preventing operation failures such as output distortion and over-amplitude, particularly due to voice coil displacement affecting magnetic flux interaction.

Innovation Solution

The system employs two voice coils with different axial lengths and amplification factors, where the shorter coil interacts with magnetic flux only when aligned, and the longer coil maintains drive force when misaligned, using a sensor to adjust amplification based on displacement to optimize power usage and prevent failures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the height of the voice coils is set to be sufficiently greater than the height of the gap, then the voice coils can be prevented from being displaced to a position offset from the gap, but the drive force acting on the voice coils becomes lower and initial sensitivity deteriorates

Engineering Contradiction:

Improveprevention of voice coil displacement from gapVSAvoiddrive force on voice coils

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The voice coil is divided into two separate coils: a first voice coil with height greater than the gap height for reliability, and a second voice coil with height equal to or less than the gap height for optimal drive force. These coils operate in different conditions based on displacement detection

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system dynamically switches between driving the first voice coil and the second voice coil based on the detected displacement of the vibration system. When displacement is within a predetermined range, the second coil is driven; when displacement exceeds this range, the first coil is driven instead

Inventive Principle:

Principle #15Dynamics

2Force

If the height of the voice coils is set to be approximately equal to the height of the gap, then the drive force is maximized, but the voice coils may be displaced to a position offset from the gap causing operation failures

Engineering Contradiction:

Improvedrive force on voice coilsVSAvoidprevention of operation failures

Core Design Contradiction:

ForceVSReliability

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system changes the operational parameter (which voice coil is driven) based on the detected displacement. When displacement is within a predetermined range, the second coil is driven; when displacement exceeds this range, the first coil is driven instead

Inventive Principle:

Principle #35Parameter changes

3Force

If the amplification factor is increased to increase drive force on the voice coils, then the drive force is improved, but power consumption increases

Engineering Contradiction:

Improvedrive force on voice coilsVSAvoidpower consumption

Core Design Contradiction:

ForceVSUse of energy by moving object

Solution Approach 1:

The system dynamically adjusts the amplification factor based on the detected displacement. When displacement is within a predetermined range, a first amplification factor is applied; when displacement exceeds this range, a second amplification factor is applied instead

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the amplification factor parameter based on operating conditions (detected displacement) to optimize the balance between drive force and power consumption

Inventive Principle:

Principle #35Parameter changes

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 approach ensures required drive force while minimizing power consumption by dynamically adjusting amplification, preventing operation failures, and maintaining audio quality.

Implementation Method 1

a sensor configured to detect a displacement of a vibration system of the loudspeaker in an axial direction of the loudspeaker

Methodology Applied

Scientific EffectSensor detection:

Implementation Method 2

a first voice coil and a second voice coil that, when viewed in a radial direction of the loudspeaker, are situated in a gap in which a magnetic flux propagates

Methodology Applied

Scientific EffectElectromagnetic interaction: Lorentz Force

Data Source

PatentEP4645907A1Acoustic system

Publication Date: 2025.11.05 ALPS ALPINE CO LTD

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AI summary

To provide "acoustic system" for obtaining required drive force with low power, first voice coil greater in height dimension than gap in which magnetic flux propagates and second voice coil equal in height dimension to gap are provided such that their height-direction centers coincide. When amplification factors of audio signal applied to first and second voice coils are defined as A1 and A2, respectively, A1 is set to 0 and A2 is set to A2st when detected displacement of loudspeaker is within displacement range where second voice coil is at position where it can properly interact with magnetic flux in gap. A2 is set to 0 and A1 is set to A1st when detected displacement is within range where A2 is not set to A2st. A2st is smaller than A1st. Ranges where second voice coil is offset from gap are included in displacement ranges where A1 is set to A1st.