Coaxial MF-HF Loudspeaker Assembly With Phase Plug Waveguide
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Solution Overview
Problem
Existing loudspeaker systems face challenges in reproducing the wide range of human auditory frequencies due to the dissimilarities between low-frequency (LF) and high-frequency (HF) drivers, leading to bandwidth limitations, destructive interference, and inefficient mid-frequency (MF) driver performance, particularly in large-scale systems.
Innovation Solution
A loudspeaker assembly with a coaxial configuration of an MF driver and an HF driver, utilizing a phase plug and waveguide design that ensures sufficient acoustic pathlength for MF wavelengths, mitigating axial limitations and enhancing driver alignment to extend the upper frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a two-way loudspeaker system combines LF and HF drivers, then the system can reproduce a wide frequency range, but the dissimilar driver characteristics cause bandwidth limitations and interference at crossover frequencies
Solution Approach 1:
The patent divides the frequency reproduction task into three separate drivers: LF driver for low frequencies, MF driver for mid frequencies (200 Hz to 6 kHz), and HF driver for high frequencies. This segmentation allows each driver to operate within its optimal bandwidth without the interference problems that occur in two-way systems at crossover frequencies.
Solution Approach 2:
The patent transitions from a conventional side-by-side driver arrangement to a coaxial configuration where the MF driver is positioned at the center of the HF driver. This dimensional reorganization allows the MF driver to be acoustically coupled to the horn through the phase plug area, enabling sufficient acoustic pathlength while maintaining compact spacing between drivers.
2Adaptability or versatility
If MF drivers are added to create a three-way system, then driver bandwidth challenges are reduced, but additional crossover regions and system complexity increase
Solution Approach 1:
The patent merges the MF and HF drivers into a single coaxial assembly where the MF driver is positioned at the center of the HF driver. The MF driver is acoustically coupled to the horn through the phase plug area, combining both drivers' functions in one integrated unit. This merging reduces the number of separate crossover regions needed compared to traditional three-way systems with independently mounted drivers.
3Area of stationary object
If horns are closely spaced to reduce interference, then array compactness improves, but the magnet diameter being larger than horn throat limits proximity and causes destructive interference
Solution Approach 1:
The patent reorganizes the driver arrangement from a lateral configuration to a coaxial configuration. By positioning the MF driver at the center of the HF driver along the acoustic axis, the design enables sufficient acoustic pathlength for MF wavelengths without requiring large lateral spacing between horn throats. This dimensional change allows closer horn spacing while maintaining acoustic performance.
Solution Approach 2:
The patent uses the phase plug structure as an intermediary element that facilitates acoustic coupling between the MF driver and the horn. The phase plug area serves as the acoustic interface through which MF sound waves are transmitted to the horn, enabling effective coupling without requiring the MF driver to be positioned far from the horn throat.
4Adaptability or versatility
If MF drivers are derived from scaled LF cone drivers, then mid-range reproduction is achieved, but efficiency and upper band response are poor due to diaphragm mass and stiffness limitations
Solution Approach 1:
The patent designs the MF driver with specific local characteristics optimized for mid-frequency reproduction. Rather than simply scaling down an LF driver, the MF driver uses a diaphragm with appropriate mass and stiffness properties for the 200 Hz to 6 kHz range. The driver is acoustically coupled to a horn through the phase plug area, providing efficient acoustic loading and improved upper band response compared to direct-radiating MF drivers.
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 configuration provides improved acoustic performance by extending the upper frequency range and reducing interference, allowing for coherent reproduction of mid-range frequencies in large-scale systems.
Implementation Method 1
a phase plug disposed between the first driver diaphragm and the second driver, the phase plug positioned within the phase plug outer housing, and defining at least one slot for providing air movement (acoustic coupling) between the first driver diaphragm and the curved passageway
Implementation Method 2
A loudspeaker assembly with a coaxial configuration of an MF driver and an HF driver, utilizing a phase plug and waveguide design that ensures sufficient acoustic pathlength for MF wavelengths, mitigating axial limitations and enhancing driver alignment to extend the upper frequency range
Implementation Method 3
An array of horns and drivers therefore, no matter how closely spaced, results in substantial destructive interference increasing in severity as frequency increases
Data Source
AI summary
A loudspeaker assembly having a waveguide, comprising: a housing comprising an outer duct and a phase plug housing; a first driver comprising a diaphragm; a second driver coaxially disposed in front of the first driver diaphragm and comprising a capsule having a rear surface, wherein a curved passageway is formed around the capsule within a duct; and a phase plug disposed between the first driver diaphragm and the second driver, the phase plug positioned within the phase plug outer housing, and defining at least one slot having an inlet for providing air movement between the first driver diaphragm and the curved passageway; wherein the rear surface of the capsule forms part of the phase plug, and a uniform gap is defined between the first driver diaphragm and the rear surface of the capsule, and wherein the first driver is a lower frequency driver than the second driver.