Segmented Horn Driver for Compact Low-Frequency Sound Reproduction
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Solution Overview
Problem
Conventional sound reproduction systems face challenges in achieving flat acoustic power response across a wide frequency range, particularly above 2 or 3 kHz, due to the limitations of horn driver designs, which result in severe high-frequency roll-off when listeners are not positioned on-axis, and the difficulty in creating compact systems that maintain low-frequency performance.
Innovation Solution
The use of a sound barrier with multiple horn sections and drivers mounted to produce sound outputs in different directions, allowing for dynamic frequency-dependent phase shift and acoustic impedance changes, enabling efficient sound reproduction in compact sizes by tapping into the horn at various points along its length and using additional air volumes for compliance, thereby minimizing harmonic distortion and extending high-frequency response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If exponential-shape curved wall horns are used to achieve flat acoustic power response, then low-frequency performance is improved, but high-frequency roll-off occurs when listeners are not positioned on-axis
Solution Approach 1:
The horn is divided into multiple sections with different expansion rates. The first horn section has a first expansion rate optimized for low-frequency performance, while the second horn section has a second expansion rate optimized for high-frequency performance. This segmentation allows each section to independently optimize for its frequency range, resolving the contradiction between low-frequency flatness and high-frequency off-axis performance.
2Volume of moving object
If horn mouth area is reduced to make the system compact, then device size is reduced, but response peaks and dips become prohibitively large
Solution Approach 1:
Different sections of the horn have different local geometric properties. The first horn section has a larger cross-sectional area with a first expansion rate, while the second horn section has a smaller cross-sectional area with a second expansion rate. This local quality variation allows the horn to maintain smooth frequency response while achieving a compact overall size, as each section is optimized for its specific function.
3Adaptability or versatility
If constant directivity horn design is used to provide consistent sound quality, then off-axis listening is improved, but low-frequency loading on drivers is reduced
Solution Approach 1:
The horn is segmented into two sections with different expansion rates. The first section provides the necessary low-frequency loading with appropriate acoustic impedance, while the second section maintains constant directivity for improved off-axis performance. This segmentation allows the system to achieve both adequate driver loading and consistent sound quality across different listening positions.
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
This approach results in a more efficient and compact sound reproduction system with improved frequency response, reduced group delay, and increased sensitivity, allowing for heretofore unattainable sound quality in practical sizes, especially for low-frequency applications below 100 Hz, while maintaining low-frequency performance and minimizing harmonic distortion.
Implementation Method 1
dynamic frequency-dependent phase shift and acoustic impedance changes
Implementation Method 2
sound outputs in different directions is provided
Data Source
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AI summary
A sound reproduction system (10) is disclosed in which a sound barrier (14) defines a horn passageway having an upstream (22) and a downstream section (24). A driver (12) is mounted at the throat (16) of the upstream section (22) so that its rearward directed output communicates with the downstream section (24). Output from the upstream section and the rearward directed output of the driver are merged at a tap point located at the beginning of the downstream section. By altering the respective areas and lengths of the upstream and downstream sections a variety of different frequency dependent responses are obtained. In one example, low-frequency response systems of heretofore unobtainable compact size are realized.