Directive Loudspeaker Waveguide with Resistive Resonators
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Solution Overview
Problem
Existing loudspeakers with waveguides face challenges in controlling directivity of sound energy, especially in smaller designs where not all drivers can be centered within the waveguide, leading to sound diffractions and deterioration of audio quality.
Innovation Solution
The solution involves acoustically connecting resistive resonators to the sub-volume of the woofer, allowing the total volume of the loudspeaker to remain small while improving the dynamic performance of the woofer and suppressing unwanted resonances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If drivers are positioned non-coaxially in smaller loudspeakers, then the total volume can be reduced, but sound diffractions occur and audio quality deteriorates
Solution Approach 1:
An acoustically transparent or reflective material is introduced as an intermediary between the non-coaxial drivers and the waveguide. This material allows the waveguide to maintain its continuous form for mid- and high-frequency directivity control while permitting low-frequency sound from non-coaxial drivers to pass through or reflect without creating harmful diffractions
Solution Approach 2:
The front surface is differentiated into regions with different acoustic properties: the waveguide region maintains continuous surfaces for directivity control, while the driver mounting regions use acoustically transparent or reflective materials that allow low-frequency energy to pass or reflect without disrupting the waveguide's directivity control function
2Adaptability or versatility
If the waveguide area is increased to extend directivity control to lower frequencies, then directivity control frequency range is improved, but the loudspeaker size increases
Solution Approach 1:
The acoustic system is segmented into different frequency ranges handled by different components: the waveguide handles mid- and high-frequency directivity control, while non-coaxial drivers with acoustically transparent/reflective materials handle low frequencies. This segmentation allows directivity control to be extended to lower frequencies without proportionally increasing the waveguide area and overall speaker size
3Adaptability or versatility
If non-coaxial drivers are covered with acoustically transparent material, then directivity control is improved, but dynamic performance of drivers deteriorates due to restricted air flow
Solution Approach 1:
The acoustic parameters of the covering material are carefully selected and optimized: the material has high acoustic transparency or reflectivity for mid- and high-frequency directivity control, while maintaining sufficient air flow permeability for low-frequency driver dynamic performance. The material's acoustic properties are tuned to different frequency ranges to balance both requirements
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 enables the formation of a continuous waveguide on the front surface of the loudspeaker for mid- and high frequencies without disturbing resonances from the bass driver, ensuring precise audio range directionality and natural sound distribution in the listening room.
Implementation Method 1
resistive resonators connected to the sub volume of the woofer such that the total volume of the loudspeaker stays as small as possible
Implementation Method 2
continuous waveguide on the front surface of the loudspeaker for mid- and high frequencies
Implementation Method 3
waveguide structure...accurate directing of the sound energy
Data Source
Figure 1
Figure 2~3
Figure 4~7
AI summary
The present invention relates to a loudspeaker (1) including an enclosure (2) having front (15) portion, side portions(21) and back portion (25) defining an inner volume (27), the front portion (15) is formed as a waveguide surface (8) and includes at least one driver (12, 13) in the center of the waveguide surface (8) and is capable to radiate the main acoustic power of the loudspeaker (1) to ambient volume (26) indirection of first acoustic axis (10), and an additional driver (4) attached to the enclosure (2). In accordance with the invention the additional driver (4) is attached inside the enclosure (2) such that a sub volume (22) is formed inside the inner volume (27), the sub volume (22) limited by the driver (4), spacers (33) between the driver (4) and the front portion (15), and the front portion (15) of the enclosure (2), and at least one port (20) is adapted to open from the sub volume (22) to ambient volume (26) either to side portion (21) or back portion (25) of the enclosure (2) and at least one resonator (40) acoustically connected to the sub volume (22), the resonator (40) being tuned to at least one of unwanted resonances of the sub volume (22).