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Speaker Speaker Line Array Knowledge Q & A

What is the goal of a high quality sound system? Provide clear coverage from the sitting position to the seat as much as possible. However, the traditional speaker group method, due to the interaction between the sound generated by the interference, in achieving this goal, there are inherent limitations. The solution is to provide a system with better sound quality (less comb filter), better coverage, and more efficient use of amplifier power. Here is an overview:

Question:

1) Covering a large number of listeners with sufficient sound pressure levels requires more than one speaker (a loudspeaker, theoretically the ideal solution, but can not provide the necessary sound pressure level or coverage).

2) Traditionally, this means that multiple trapezoidal speakers are arranged as compact as possible and a speaker covers a particular area. This is an attempt to minimize the overlap of the destructive overlay (which causes time arrival / phase irregularities and the formation of comb filtering, uneven frequency response, poor sharpness, etc.). The result is a traditional fan-shaped multi-trapezoidal sound array.

3) Even with strict graphical control, the pattern overlap between adjacent devices still occurs, resulting in interference with frequency and position (comb filtering) due to different path lengths and signal arrival times. The resulting offset, from sitting to sitting, causes extensive changes 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 be directed to a given listener area. The total sound pressure level is therefore limited by the capabilities of the set of units. An attempt is made to increase the phase offset by increasing the sound pressure level of a given area (substantially making the array flat) by pointing a plurality of sound sources to the same listener area, due to the overlapping pattern (comb filter).

5) The traditional system is projected by the spherical wave front, evenly expanding in both horizontal and vertical planes. The beats earbuds sound pressure level (SPL) obeys the inverse square law, which indicates that the sound pressure level drops by 6 dB when the distance is doubled. The practical effect is that for a conventional system, in order to send enough sound pressure level to the back of the overlay, it is possible to cover the front of the pattern.

6) In the process of trying to provide sufficient sound pressure level, as the number of sound units increases, various arrival times and phase cancellation form a chaotic sound field. Therefore, in order to overcome the room within the total sound pressure level on the phase offset effect, requiring additional power.

Solution:

1) The solution to these problems is to create a virtual single source. This theoretically ideal solution (by definition) eliminates pattern overlaps, phase offsets from adjacent sound sources, and so on. However, the implementation in the entire audio frequency band becomes complicated.

2) The traditional line beats by dre array concept was developed by Olson, Beranek, and others. In 1988, Dr. Christian Heil and Professor Marcel cheap beats Urban were engaged in the study, resulting in the definition of the required conditions. Under these conditions, it is possible to effectively couple a separate sound source in the audible frequency range to create a virtual single source. The relevant parameters include wavelength, surface area of ??each sound source, relative sound source spacing.

3) An integral part of this study was Professor Heil and Urban Professor who applied Fresnel analysis to understand the phenomenon of audio interference. Based on the principle of early 1800 (analysis of optical interference), the criterion of L-ACOUSTICS wavefront correction technique is determined.

4) Prof. Heil and Urban, who published these papers in AES in March 1992,

They can be summarized as follows:

If one or both of the following conditions are met, they are arranged in an array on a flat or continuous curved surface and there is a set of sound sources with regular spacing between the sound sources, equivalent to a single individual of the same size as the entire set Sound source:

A. The spacing between the sound sources (step length, defined as the distance between the acoustic centers of the adjacent sound sources), at all frequencies in the operating band, is less than half the wavelength.

B. The individual wave sources generated by the individual sound sources are planar (flat and rectangular, have a constant phase at the output of the sound source), and the combined area of ??the sound source (effective radiation coefficient) is at least filled with the target radiation surface area Of the 80%.

5) The performance of the source array and the design of the individual speaker box are strictly governed by the physical principles of the WST guidelines.

6) The dimensions of the loudspeaker dominate the middle and low frequency speakers to meet the first criterion, but the high frequency compression drive can not be dominated (the dimensions are too large).

7) For proper coupling, the high frequency part must meet the second criterion. This leads directly to the patented DOSC waveguide, which is the first high-frequency device capable of producing rectangular, constant phase-plane outputs. This patented DOSC waveguide is the heart of the L-ACOUSTICSV-DOSC, dV-DOSC, ARCS system.

8) L-ACOUSTICS The application of these concepts in the entire frequency range, the formation of a virtual single unit line sound source system, if necessary, it can be developed and cleverly processed to cheap beats produce the required coverage graphics.

9) The correct application of the wavefront correction technique, the linear sound source system produces a cylindrical wave front, which can be reduced by 3 dB when the distance is doubled (conversely, the spherical wavefront of the traditional point source system, Doubled, down 6dB), from front to back, the formation of more uniform coverage.