Loudspeaker Horn Segmentation for Cinema Beamwidth Control
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Solution Overview
Problem
In cinema sound reinforcement systems, large or deeper waveguide horns used to maintain beamwidth control over a wide frequency range suffer from beam spreading due to reflections from the cinema screen, degrading frequency response and beamwidth control.
Innovation Solution
A two-way loudspeaker system with a high channel transducer and low channel cone transducer mounted in close proximity, combined with signal processing circuits that allow the horn to operate below its normal cut-off frequency, controlling beamwidth over a wide frequency range without the need for larger horns, thereby reducing the impact of screen reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If larger waveguide horns are used to maintain beamwidth control over a wide frequency range, then beamwidth control is improved, but beam spreading occurs due to reflections from the cinema screen
Solution Approach 1:
The patent divides the horn into multiple sections with different expansion rates. The first section has a slower expansion rate while the second section has a faster expansion rate, allowing each section to be optimized for different functions. This segmentation enables beamwidth control without requiring a single large horn structure that would cause screen reflections.
Solution Approach 2:
Different sections of the horn are given different geometric properties - the first section has a more gradual expansion while the second section has a steeper expansion. This local differentiation allows the horn to control beamwidth effectively without needing to be uniformly large throughout, reducing the impact on screen reflections.
2Manufacturing precision
If the horn is made physically deeper and larger to obtain control at lower frequencies, then beamwidth control at low frequencies is improved, but the affect of screen reflections on frequency response and beamwidth control increases
Solution Approach 1:
The horn is divided into two sections where the first section handles the transition from high to mid frequencies with a slower expansion, while the second section handles mid to low frequencies with a faster expansion. This allows low frequency control without requiring the entire horn to be excessively deep, minimizing screen reflection effects.
Solution Approach 2:
The patent uses a two-dimensional cross-sectional view showing the horn expanding in both vertical and horizontal dimensions. By controlling the expansion in multiple dimensions rather than simply increasing depth, the horn achieves low frequency control while maintaining a compact profile that reduces screen interaction.
3Device complexity
If a single waveguide horn is used for full range coverage, then device complexity is reduced, but beamwidth control over the entire frequency range cannot be achieved
Solution Approach 1:
The single horn is segmented into two distinct sections with different expansion characteristics. This internal segmentation allows the horn to provide full-range beamwidth control without requiring multiple separate horns or complex arrays, maintaining relative simplicity while achieving the desired 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 system achieves constant beamwidth control in both horizontal and vertical planes from 15 kHz down to 500 Hz, reducing beam spreading and maintaining frequency response integrity, even when placed behind a cinema screen.
Implementation Method 1
a waveguide horn (13) having a front surface, and a low frequency transducer (17) mounted on the front surface of the waveguide horn (13)
Implementation Method 2
using loudspeakers having large or deeper waveguide horns can detrimentally affect the beamwidth and frequency response of the loudspeaker system due to waves reflecting back and forth between the screen and the surface of the horn
Implementation Method 3
a low frequency transducer (17) mounted on the front surface of the waveguide horn (13)
Data Source
AI summary
A loudspeaker system has a high frequency channel for driving a horn loaded high frequency transducer, and a low frequency channel for driving a low frequency transducer. A signal processing circuit is provided which has at least one first order and at least one second order cross-over circuit portion in the high channel and at least one first order and at least one second order cross-over circuit portion in the low frequency channel. These cross-over portions produce a cross-over frequency range for the loudspeaker system that is below the cut-off frequency of the horn. The signal processing circuit, including its cross-over circuit portions and in conjunction with the design of the expansion walls of the horn, extends vertical beamwidth control of the acoustic output of the loudspeaker system at the loudspeaker system's lower frequency range.