Phasing Plug Apertures for Compression Driver Reflection Control
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Solution Overview
Problem
Compression drivers face issues with radial standing waves and high-frequency resonances due to the small radial dimensions of annular diaphragms, leading to irregular frequency responses and potential distortion, which existing solutions like circular slots fail to adequately address.
Innovation Solution
A phasing plug assembly with a base portion and hub portion featuring apertures arranged in a sawtooth or sinusoidal pattern, providing a continuous, reflection-free air path that minimizes high-frequency reflections and enhances sound wave propagation without abrupt turns, thereby smoothing the frequency response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the compression chamber volume is reduced to keep the diaphragm close to the phasing plug, then high frequency signal transmission is improved, but nonlinear compression distortion and rub/buzz increase
Solution Approach 1:
The compression chamber volume is segmented into multiple smaller volumes by introducing partition structures (such as radial walls or diaphragms) that divide the chamber into separate sections. This allows the overall chamber to maintain a larger volume for reduced nonlinear compression, while each segmented section maintains a smaller effective volume for improved high-frequency signal transmission, thereby resolving the contradiction between these two requirements.
2Object-generated harmful factors
If circular slots are used in the phasing plug to suppress air resonances, then resonance suppression is achieved, but high-frequency sound pressure level irregularity remains due to diaphragm breakups
Solution Approach 1:
The patent replaces traditional circular slots with asymmetrically shaped apertures (such as rectangular, elliptical, or irregular shapes) in the phasing plug. This asymmetric configuration disrupts the symmetric resonance patterns caused by circular slots, providing better averaging and randomization of sound pressure. The asymmetric geometry helps mitigate both air resonances and diaphragm breakup effects, achieving smoother high-frequency response.
3Adaptability or versatility
If the phasing plug area is reduced to match the smaller annular diaphragm, then directivity control is improved, but sound wave reflections increase due to abrupt area transitions
Solution Approach 1:
The patent employs curved or tapered transitions in the phasing plug geometry, replacing abrupt area changes with gradual curved surfaces. The phasing plug features a tapered bore or curved walls that provide a smooth acoustic impedance transition from the compression chamber to the horn. This curved geometry reduces sound wave reflections while maintaining the area reduction needed for directivity control, resolving the contradiction between these two requirements.
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 solution achieves a smooth and scalable frequency response with reduced reflections and resonances, ensuring a continuous acoustical connection from the compression chamber to the exit, even in large format drivers, with improved directivity and extended frequency range.
Implementation Method 1
The volume of air entrapped in the compression chamber is characterized by an acoustical compliance which is proportional to the volume of compression chamber
Implementation Method 2
The outer surface of the hub portion having a sawtooth type pattern or a sinusoidal type pattern that corresponds to a configuration of the plurality of apertures
Data Source
Figure 1~2
Figure 3A~3B
Figure 4~5
AI summary
A compression driver includes a phasing plug having a base portion with a first side and an opposed second side, and includes a hub portion extending outwardly from the first side along a central axis, the hub portion including an outer surface. The base portion includes a plurality of apertures that extend therethrough from the first side to the second side, the apertures arranged generally circumferentially about the central axis and oriented generally parallel to the outer surface of the hub portion. A diaphragm is disposed adjacent the phasing plug second side, and a compression chamber is defined between the diaphragm and the phasing plug. A housing is positioned on the phasing plug first side, the housing having a central aperture generally aligned with the hub portion and forming an exit of the compression driver, the housing having an inner surface which forms a waveguide with the outer surface of the hub portion.