Panel Loudspeaker Actuator Coil Winding Density
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Solution Overview
Problem
Conventional panel audio loudspeaker magnet systems face performance limitations due to increased inductance and electrical impedance at high frequencies, and temperature and electrical resistance issues that reduce maximum force generation and acoustic output.
Innovation Solution
The design incorporates a coil with varying winding densities, where one region has a lower winding density and another region has a higher winding density than the average, along with a cap for improved mechanical strength, to enhance force generation and frequency response, and includes a magnet assembly suspended by compliant members for increased robustness and resonance tuning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional uniform coil winding density is used, then manufacturing is simple, but force generation efficiency is limited and high frequency performance deteriorates
Solution Approach 1:
The coil is designed with non-uniform winding density where different axial regions have different numbers of windings. Specifically, the coil has a first winding density in a first axial region and a second winding density in a second axial region, with the ratio between them optimized to maximize force generation in the air gap region while maintaining manufacturing feasibility. This local variation in winding density directly addresses the force generation efficiency problem without requiring complete redesign of the entire actuator system.
2Force
If soft magnetic material is used in magnet assembly, then magnetic field generation is effective, but inductance and electrical impedance increase with frequency reducing acoustic output
Solution Approach 1:
The patent optimizes the parameters of the soft magnetic material including permeability, saturation flux density, and loss characteristics. By selecting materials and designing the magnet assembly geometry with specific parameter ranges, the system achieves effective magnetic field generation while controlling the frequency-dependent increase in inductance and electrical impedance that would otherwise reduce acoustic output at high frequencies.
3Force
If high current is used to increase force, then maximum force generation improves, but temperature and electrical resistance increase causing power compression
Solution Approach 1:
The non-uniform winding density distribution concentrates more windings in regions where the magnetic field is strongest (within the air gap), which maximizes force generation efficiency per unit current. This allows the actuator to achieve higher maximum force at lower overall current levels, thereby reducing I²R heating and power compression effects that would otherwise limit performance.
4Reliability
If coil mechanical compliance is increased, then robustness improves, but resonance control becomes more difficult
Solution Approach 1:
The coil's mechanical compliance is varied axially to match the magnetic field distribution. Regions with higher winding density have lower compliance while regions with lower winding density have higher compliance. This localized compliance variation provides robustness in high-stress areas while maintaining controllability of resonance characteristics through the overall compliance gradient, balancing reliability with ease of resonance tuning.
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 configuration provides improved efficiency, robustness, and frequency response, allowing for higher force generation at the same voltage and additional resonance modes tailored for specific audio frequencies, enhancing the overall performance of panel audio loudspeakers.
Implementation Method 1
An electronic control module is electrically coupled to the coil and programmed to energize the coil to cause axial motion of the magnet assembly relative to the coil
Implementation Method 2
The magnet assembly can be suspended from the panel by one or more compliant members
Implementation Method 3
The first and second regions can be configured so that the panel audio loudspeaker includes a resonant mode at a frequency in a range from 5 kHz to 20 kHz that is not present in a comparable panel audio loudspeaker having a coil with a uniform coil winding density
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A panel audio loudspeaker includes a panel and an actuator rigidly coupled to a surface of the panel. The actuator includes: a magnet assembly that includes a permanent magnet arranged within a cup, wherein an air gap exists between sidewalls of the cup and the permanent magnet; and a coil rigidly coupled to the panel, the coil including a length of an electrically conducing wire wound in a coil and extending along an axis. The coil includes a first region having a first winding density and a second region having a second winding density higher than the first winding density, the second region at least partially extending into the air gap of the magnet assembly.