Twisted Radial Phase Plug for Loudspeaker Wavefront Control
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Solution Overview
Problem
Horn-loaded diaphragm type loudspeakers suffer from phase differences in sound waves reaching the throat, leading to distortion and diminished high-frequency sound due to unequal path lengths, which existing phase plugs have not adequately addressed.
Innovation Solution
A phase plug with a central cone and radially extending vanes that twist and taper, creating radially twisted phase leveling channels to ensure planar wavefronts and minimize diffraction, thereby reducing phase differences and distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional horn loading is used to control sound radiation direction and improve impedance matching, then loudspeaker efficiency is improved, but phase differences occur in sound waves reaching the horn throat leading to distortion and diminished high-frequency sound
Solution Approach 1:
The phase plug is segmented into multiple radial channels separated by vanes, with each channel receiving sound from a specific radial section of the diaphragm. This segmentation allows independent path length control for different radial portions, enabling phase alignment while maintaining the horn's efficient sound radiation.
Solution Approach 2:
Different radial sections of the phase plug have different channel lengths and geometries tailored to their specific function. The vanes are positioned and dimensioned to create locally optimized paths that compensate for the varying distances from different diaphragm portions to the horn throat, achieving uniform phase across the entire sound field.
2Manufacturing precision
If the sound front is made planar to reduce distortion at high frequencies, then sound quality is improved, but the path length differences between various diaphragm portions must be precisely controlled increasing device complexity
Solution Approach 1:
The phase plug employs a spherical diaphragm surface that naturally focuses sound waves to a common point (the horn throat). This spherical geometry, combined with radially arranged channels of equal length, automatically equalizes path lengths without requiring complex variable-depth structures, achieving planar wavefronts with relatively simple construction.
Solution Approach 2:
The phase plug merges the functions of path length equalization, wavefront shaping, and impedance transformation into a single integrated structure. The radial vanes and channels are combined with the horn throat geometry to simultaneously achieve phase alignment and efficient sound radiation, reducing the need for separate components.
3Ease of manufacture
If radial channels are used instead of annular channels to simplify manufacture, then ease of manufacture is improved, but diffraction effects may increase
Solution Approach 1:
The radial vanes are designed with locally optimized geometries where the aperture width and channel depth vary along the radial direction. This local quality control minimizes diffraction effects at each radial position while maintaining the overall simplicity of the radial channel structure, balancing manufacturability with acoustic performance.
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 effectively generates acoustic planar wavefronts, reducing distortion and enhancing high-frequency sound reproduction by maintaining consistent phase across the loudspeaker diaphragm and horn throat interface.
Implementation Method 1
Wente proposed a 'sound translating device,' or what today would be called a phase plug, to control path distance between sections of a loudspeaker diaphragm and a horn throat
Implementation Method 2
generation of a sound field characterized by planar wavefronts from a diaphragm type loudspeaker reduces distortion at a point of reception, particularly at high frequencies
Data Source
AI summary
A loudspeaker assembly comprises a casing with a diaphragm loudspeaker mounted in the casing. A phase plug is mounted in the casing adjacent the diaphragm loudspeaker. The phase plug has a central cone with a longitudinal axis extending from an input end adjacent the diaphragm loudspeaker to an output end with its base at the input end tapering to an apex at the output end. A plurality of vanes extend radially outwardly from the central cone with the plurality of vanes being thickest at the input end and progressively thinning toward the output end. Radially outward edges of the plurality of vanes are twisted relative to the longitudinal axis with the degree of twist being progressively greater with increasing proximity to the output end. The plurality of vanes tapers in width along their longitudinal extent from the input end to the output end.