Bass-Reflex Speaker Cabinet Recessed Port Phase Shift Reduction
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Solution Overview
Problem
Conventional bass-reflex speaker cabinets experience significant phase shifts and resonance frequency peaks, leading to uneven frequency response and directional radiation variations, which cannot be corrected by signal processing.
Innovation Solution
Incorporating a recess in the port's inlet, which is formed by edges of the casing, to reduce phase shifts between the loudspeaker and port, thereby smoothing the frequency response and stabilizing angular radiation patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional port design is used in a bass-reflex cabinet, then the low-frequency radiation efficiency is improved, but significant phase shifts and resonance frequency peaks occur causing uneven frequency response
Solution Approach 1:
The patent modifies the port geometry by introducing a recess at the inlet, changing the physical parameters of the port structure. This geometric parameter change alters the acoustic impedance and reduces higher-order resonance frequencies, thereby smoothing the frequency response while maintaining low-frequency radiation efficiency
Solution Approach 2:
The recess introduced in the port inlet creates a curved or non-linear geometric feature that modifies the acoustic flow path. This curvature change helps to reduce phase shifts and resonance peaks by altering the way sound waves propagate through the port, leading to a flatter frequency response
2Power
If a conventional port design is used in a bass-reflex cabinet, then the low-frequency power is enhanced, but the angular coverage and radiation consistency deteriorate due to phase shifts
Solution Approach 1:
By modifying the port inlet geometry with a recess, the patent changes the acoustic parameters that govern radiation patterns. This geometric modification reduces phase shifts between the port and loudspeaker radiation, resulting in more consistent angular coverage and radiation patterns across different frequencies
3Device complexity
If the port casing is formed by cabinet walls to reduce complexity, then the device complexity is reduced, but the manufacturing precision and control over resonance frequencies become more difficult
Solution Approach 1:
The patent applies a localized modification (the recess) only at the port inlet area, while the rest of the port casing can continue to be formed by cabinet walls. This local quality change allows for precise control of resonance frequencies through the recess geometry without requiring complete redesign of the entire port structure, thus maintaining ease of manufacture while improving resonance control
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 recess design minimizes higher-order resonance frequencies, resulting in a flatter frequency response and more consistent radiation patterns across various orientations, improving the overall acoustic performance of the speaker cabinet.
Implementation Method 1
the inlet of the port has at least one recess in the casing, for example formed by at least one edge of the casing... to reduce phase shifts between the loudspeaker and port
Implementation Method 2
a port (or several ports) radiating around a tuning frequency fc (EV curve)... the loudspeaker and the port radiate in phase which increases the efficiency of the radiation
Implementation Method 3
the two resonance frequencies (f1 and f2) of the system and the tuning frequency (fc) situated between these two resonance frequencies... These two resonance frequencies f1 and f2 are characteristic of a system with two degrees of freedom
Data Source
AI summary
The speaker cabinet (1) includes at least one loudspeaker (2) and at least one port (3), the port having an outlet (32) formed in a wall of the cabinet (1), an inlet (31) inside the cabinet (1), and a casing connecting the inlet (32) and the outlet (31) together, the inlet (32) of the port (3) further having at least one recess in the casing.