What is the goal of a high-quality sound system? Provides a clear, full-range coverage that is as consistent as possible from sitting to sitting. However, the conventional speaker group method, due to the interference caused by the interaction between the sounds, has inherent limitations in achieving this goal. The solution is to provide a system with better sound quality (less comb filtering), better coverage, and more efficient use of amplifier power. Here is an overview:
problem:
1) Covering a large number of listeners with sufficient sound pressure level, requiring multiple speakers (one speaker, which is theoretically the ideal solution, but does not provide the necessary sound pressure level or coverage).
2) Traditionally, this means that multiple trapezoidal speakers are arranged as compact as possible, with one speaker covering a specific area. This is an attempt to minimize the overlap of destructive overlay graphics (which causes time arrival/phase irregularities and comb filtering, uneven frequency response, poor clarity, etc.). The result is a traditional fan-shaped multi-ladder audio array.
3) Even with strict graphics control, pattern overlap between adjacent devices still occurs, causing interference with frequency and position due to different path lengths and signal arrival times (comb filtering). The resulting offset, from sitting to sitting, causes wide variations in frequency response and sound pressure levels.
4) Another inherent limitation of the sector array is that in order to reduce the pattern overlap, only one set of speaker units should point to a given listener area. The total sound pressure level is therefore limited by the capabilities of the set of units. Attempting to increase the sound pressure level of a given area by moving multiple sound sources to the same listener area (essentially flattening the array) increases phase cancellation due to overlapping patterns (comb filtering).
5) The traditional system projects a spherical wavefront that spreads evenly in both horizontal and vertical planes. The sound pressure level (SPL) obeys the inverse square law, which shows that when the distance is doubled, the sound pressure level drops by 6 dB. The practical effect is that for conventional systems, in order to send enough sound pressure level to the back of the overlay pattern, the front of the overlay pattern may be too loud.
6) In an attempt to provide a sufficient sound pressure level, as the number of acoustic units increases, various arrival times and phases cancel out a chaotic sound field. Therefore, in order to overcome the phase cancellation effect in the room at the total sound pressure level, additional power is required.
Solution:
1) The solution to these problems is to create a virtual mono source. This theoretically ideal solution (by definition) eliminates pattern overlap, phase cancellation from neighboring sources, and more. However, implementations throughout the audio band have become complicated.
2) The traditional line array concept was developed by Olson, Beranek and others. In 1988, Dr. Christian Heil and Professor Marcel Urban said that the results required were defined. Under these conditions, individual sound sources can be effectively coupled in an audible frequency range to create a virtual mono source. Relevant parameters include wavelength, surface area of ​​each sound source, and relative sound source spacing.
3) An integral part of this research is the application of Fresnel analysis to the understanding of audio interference phenomena by Dr. Heil and Professor Urban. Using the principles of the early 1800s (analytical optical interference), the criteria for L-ACOUSTICS wavefront correction techniques were determined.
4) Dr. Heil and Professor Urban's paper published in AES in March 1992 cited these guidelines.
They can be summarized as follows:
If one or both of the following conditions are met, a set of sound sources arranged in an array and having a regular spacing between sound sources on a planar or continuously curved surface is equivalent to a single size having the same size as the entire set Sound source:
a. The spacing between sound sources (step size, defined as the distance between the acoustic centers of adjacent sound sources), is less than half the wavelength at all frequencies in the operating band.
b. The wavefront generated by a single sound source is planar (flat and rectangular with a constant phase at the output of the sound source), and the combined area of ​​the sound source (effective emissivity) fills at least the target radiating surface area 80%.
5) The performance of the line source array and the design of the individual speaker box are strictly governed by the physics of the WST guidelines.
6) The size of the speaker dominates the mid-low frequency speaker to meet the first criterion, but the high-frequency compression driver does not control (the size is too large).
7) For proper coupling, the high frequency part must comply with the second criterion. This directly led to the patented DOSC waveguide, which was the first high-frequency device capable of producing a rectangular, invariant phase plane output. This patented DOSC waveguide is the heart of the L-ACOUSTICSV-DOSC, dV-DOSC, and ARCS systems.
8) L-ACOUSTICS applies these concepts to form a virtual single-unit line source system over the entire frequency range, which can be developed and subtly processed as necessary to produce the required overlay pattern.
9) Correctly apply the wavefront correction technique, the cylindrical wavefront generated by the line source system can be reduced by 3dB when the distance is doubled (in contrast, the spherical wavefront of the traditional point source system, when the distance When doubled, it drops by 6dB), forming a more uniform coverage from front to back.
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