Coaxial Loudspeaker Waveguide Segmentation for Directivity Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Coaxial loudspeakers suffer from compromised directivity patterns across their frequency spectrum due to axisymmetric cone shapes imposing a non-optimal high-frequency directivity pattern and beamwidth, which is further compromised by the need for a steep cone neck to ensure good low/mid-frequency performance.
Innovation Solution
The implementation of a coaxial loudspeaker design with a first waveguide extending from a low/mid-frequency unit, a second waveguide extending from the first, and a third waveguide extending from the second, forming an enlarged effective waveguide system that includes a static waveguide with a flange and apertures to minimize interference and enhance acoustic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an axisymmetric cone shape is used for the low/mid-frequency unit, then good low/mid-frequency performance is achieved, but the high-frequency directivity pattern is compromised and beamwidth decreases with increasing frequency
Solution Approach 1:
The waveguide is divided into multiple sections (first, second, and third waveguides) with different geometries. The first waveguide has a steep neck angle for low/mid-frequency performance, while the second and third waveguides have progressively shallower angles to control high-frequency directivity independently, allowing each section to optimize for its frequency range without compromising the other.
2Reliability
If the cone neck angle is made steep to ensure good low/mid-frequency performance, then low/mid-frequency response is improved, but the high-frequency beamwidth decreases further compromising the design
Solution Approach 1:
The solution transitions from a single-dimensional cone geometry to a multi-dimensional waveguide system where the cross-sectional area changes progressively through multiple sections. This allows independent control of acoustic impedance at different stages of sound wave propagation, enabling steep initial angles for low frequencies while using subsequent shallower angles to maintain high-frequency beamwidth.
3Reliability
If discrete axially offset acoustic sources are used, then system directivity is improved through the crossover region, but off-axis phase cancellation occurs
Solution Approach 1:
The low/mid-frequency cone and high-frequency waveguide are merged into a coaxial arrangement where the waveguide extends from the cone's axis. This integration ensures that sound waves from both units propagate along the same axial path, eliminating the off-axis phase cancellation that occurs with offset sources while maintaining improved directivity through the crossover region.
4Shape
If acoustic elements are occluded to improve directivity, then directivity pattern is enhanced, but acoustic performance is impaired
Solution Approach 1:
Different sections of the waveguide have different geometric properties tailored to specific functions. The first waveguide section has a steep neck angle optimized for low/mid-frequency coupling, while the second and third sections have progressively shallower angles optimized for high-frequency directivity control. This local optimization allows each section to enhance specific aspects of acoustic performance without impairing overall system reliability.
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 provides improved efficiency and performance by reducing occlusion, enhancing acoustic dispersion, and maintaining consistent sound pressure level across a broader frequency range, addressing the compromised directivity issues of conventional coaxial loudspeakers.
Implementation Method 1
a first waveguide extending from a low/mid-frequency unit, a second waveguide extending from the first, and a third waveguide extending from the second
Implementation Method 2
The third waveguide is arranged to extend substantially, and preferably directly, in prolongation of at least a portion of the first unit, preferably in a region where no second waveguide is provided
Data Source
Figure 1
Figure 2a
Figure 2b
AI summary
A coaxial loudspeaker apparatus (10) comprising: a first unit, being arranged to propagate sound in a first frequency range; a second unit, being arranged to propagate sound in a second frequency range that is higher than the first frequency range, comprising a first waveguide (30); a second waveguide (60) arranged to extend substantially in prolongation of the first waveguide (30); and a third waveguide (100) arranged to extend substantially in prolongation of the second waveguide (60).