Bobbin Reinforcement for Speaker Distortion Control
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Solution Overview
Problem
Conventional speakers face issues with distortion and decreased sound pressure due to low rigidity of the bobbin, which can lead to deformation and nonlinear distortion, especially when the intermediate portion of the bobbin is not reinforced, potentially causing coil wire disconnection.
Innovation Solution
A speaker design that includes a bobbin reinforcement portion extending from the opening end toward the intermediate portion, opposing the vibration plate fixed portion, and a cap member with a cylindrical portion and bottom surface portion to enhance the rigidity of the bobbin and prevent deformation, while maintaining a lightweight non-metallic bobbin material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the rigidity of the bobbin is increased to prevent distortion and extra vibration, then sound quality improves, but the mass of the bobbin increases too much causing decrease in sound pressure
Solution Approach 1:
The bobbin is divided into multiple portions: a first portion with larger diameter housing the voice coil, and a second portion with smaller diameter at the opening end. This segmentation allows the bobbin to have sufficient rigidity where needed while maintaining lightweight properties overall, preventing both distortion and excessive mass.
Solution Approach 2:
The bobbin is designed with non-uniform thickness: the wall thickness at the first portion (voice coil housing) is greater than at the second portion (opening end). This local quality variation provides enhanced rigidity and strength at the critical voice coil mounting area while keeping the overall mass low, preventing distortion without sacrificing sound pressure.
2Ease of manufacture
If the intermediate portion of the bobbin is not reinforced, then the bobbin remains lightweight and easy to manufacture, but distortion occurs in the bobbin and vibration plate during sound generation driving operation
Solution Approach 1:
The bobbin is pre-designed with a specific structural configuration featuring a first portion with larger diameter and greater wall thickness, and a second portion with smaller diameter and lesser wall thickness. This preliminary structural action ensures that the intermediate portion has sufficient rigidity to prevent distortion during operation, while maintaining ease of manufacture through a straightforward two-section design.
3Device complexity
If stress concentrates on the vibration plate fixed portion in the bobbin, then the structure is simple, but the bobbin of the vibration plate fixed portion is easily deformed
Solution Approach 1:
The bobbin features localized quality variation with greater wall thickness at the first portion where the voice coil is wound and the vibration plate is fixed. This local reinforcement at the stress concentration area prevents deformation at the fixed portion while maintaining overall structural simplicity and avoiding complex reinforcement structures.
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 reinforcement of the bobbin and vibration plate fixed portion improves the speaker's rigidity, reduces distortion, and prevents coil wire disconnection, maintaining sound pressure and linearity while keeping the bobbin lightweight and cost-effective.
Implementation Method 1
a voice coil wound on the bobbin and located inside the magnetic gap; and a vibration plate disposed between the frame portion and the bobbin, in which the vibration plate is fixed to a vibration plate fixed portion located at an outer surface of an intermediate portion spaced away from an opening end portion of the bobbin
Data Source
AI summary
A cap member is attached to an opening end portion of a bobbin on which a voice coil is wound. The cap member includes a bobbin reinforcement portion including a cylindrical portion and a bottom surface portion. The cylindrical portion opposes an inner surface of the bobbin, and the cylindrical portion and the inner surface of the bobbin are fixed to each other in at least a vibration plate fixed portion and a damper member fixed portion.