Loudspeaker Negative Stiffness Adsorptive Material

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Solution Overview

Problem

Conventional loudspeaker apparatuses with small cabinets face difficulties in reproducing low-frequency sounds due to high acoustic stiffness, which limits the expansion of the low-frequency sound reproduction band and results in increased size, cost, and distortion.

Innovation Solution

Incorporating an adsorptive material like activated charcoal or zeolite inside the housing and a negative stiffness generating mechanism, which includes a non-magnet member and magnetic circuits, to reduce acoustic stiffness and enhance low-frequency sound reproduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If a small-volume cabinet is used in portable loudspeaker apparatus, then the apparatus becomes more portable and compact, but the acoustic stiffness becomes large which prevents sufficient low-frequency sound reproduction

Engineering Contradiction:

Improvecabinet volumeVSAvoidacoustic stiffness

Core Design Contradiction:

Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an adsorptive material with porous structure inside the cabinet to reduce acoustic stiffness. The porous structure allows the material to adsorb gas molecules, effectively reducing the acoustic stiffness without significantly increasing the cabinet volume, thus resolving the contradiction between small cabinet size and low-frequency sound reproduction capability

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The patent changes the physical parameters of the cabinet interior by introducing adsorptive material that modifies the acoustic properties. This parameter change reduces the acoustic stiffness value, enabling better low-frequency reproduction while maintaining the small cabinet volume for portability

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If a negative stiffness generating mechanism is used to reduce acoustic stiffness, then low-frequency sound reproduction is improved, but the size and cost of the magnet increase

Engineering Contradiction:

Improveacoustic stiffnessVSAvoidmagnet size

Core Design Contradiction:

Object-affected harmful factorsVSWeight of stationary object

Solution Approach 1:

The patent introduces an adsorptive material as an intermediary substance that mediates the reduction of acoustic stiffness. Instead of relying solely on a large magnet to generate negative stiffness, the adsorptive material acts as an intermediary that reduces the required negative stiffness magnitude, thereby allowing for smaller, less expensive magnets

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent combines the adsorptive material with the negative stiffness generating mechanism to create a composite system. This combination achieves the desired reduction in acoustic stiffness more effectively than the magnet alone, reducing the burden on the magnet and allowing for smaller size and lower cost

Inventive Principle:

Principle #40Composite materials

3Object-affected harmful factors

If a strong negative stiffness generating mechanism is used to expand the low-frequency reproduction band, then sound quality improves, but distortion increases

Engineering Contradiction:

Improvelow-frequency reproduction bandVSAvoiddistortion

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The patent optimizes the parameters of the adsorptive material and negative stiffness generating mechanism to achieve the desired low-frequency reproduction band expansion while controlling distortion. By carefully selecting the adsorptive material properties and mechanism parameters, the system achieves improved sound quality without excessive distortion

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

The combination of adsorptive material and negative stiffness generating mechanism reduces the required negative stiffness, allowing for a larger low-frequency sound reproduction band without increasing the size or cost of the magnet, thus improving sound quality and reducing distortion.

Implementation Method 1

an adsorptive material provided inside the housing, for physically adsorbing gas inside the housing

Methodology Applied

Scientific EffectPhysical adsorption: Adsorption

Implementation Method 2

a negative stiffness generating mechanism provided inside the housing, for reducing an acoustic stiffness inside the housing, the acoustic stiffness acting on the diaphragm

Methodology Applied

Scientific EffectMagnetic repulsion force: Magnetic Field

Data Source

PatentUS7953240B2Loudspeaker apparatus

Publication Date: 2011.05.31 PANASONIC HOLDINGS CORP

AI summary

A loudspeaker apparatus comprises a housing, an adsorptive material provided inside the housing, for physically adsorbing gas inside the housing, a vibration section including a diaphragm and provided in an opening formed in the housing, a drive section for driving the diaphragm to generate sound from the diaphragm, and a negative stiffness generating mechanism provided inside the housing, for reducing an acoustic stiffness inside the housing, the acoustic stiffness acting on the diaphragm.