The past, present and future of linear array applications.

In recent years, linear array loudspeaker system has been widely used in large-scale sound amplification sites with its unique advantages. Linear array loudspeaker system is produced in response to market demand and is also the product of high-tech, so it has attracted much attention.


Several Linear Array Loudspeakers

I. Generation of Linear Array Loudspeaker System

In the 1960s and 1970s, rock and roll music, represented by the Beatles, rose in Europe and the United States. There were hundreds of thousands of spectators who went to the square to watch the rock concert. The sound reinforcement was a big problem.

For example, 600,000 people attended a rock concert in New Jersey, England, on September 3, 1977. The sound reinforcement system uses a "tower" composed of multiple speakers stacked together, which is very troublesome to install and debug.

After careful design and debugging, a lot of energy is spent, and the sound reinforcement effect is always unsatisfactory. This phenomenon provides a market information. Large-scale tours require sound reinforcement systems with high power and easy installation and debugging.

Some large companies focus on market demand and are committed to developing high-power, far-projection sound amplification systems. From the acoustical point of view, there are two ways to achieve high power and far projection effect.

One is the horn.


The sound energy can be radiated in one direction through the horn, which can control the directivity, improve the radiation efficiency and achieve the effect of long-distance projection. For example, in the 1950s, we used a large trumpet for the broadcasting systems of Jinmen and Mazu. One trumpet was more than ten meters long, and the transmission distance was several kilometers. The research of the horn has successfully developed the constant directivity horn loudspeaker, the multi-drive unit horn loudspeaker and so on.


02 Another is the speaker array.

The loudspeaker array, which was proposed in the 1930s, uses interference principle to control directivity. In fact, at that time, a kind of column speaker - sound column was popular. Sound column has relatively narrow vertical directivity, but there are still some problems to be overcome, such as insufficient power, short projection distance, dynamic sound and bandwidth. Some big companies have their own priorities according to their own circumstances.

French L-Acoustics first introduced the V-DOSC system in 1993. It is an array of single speakers. Its working principle is similar to that of sound column. Its vertical directivity can be controlled by the number of cell boxes, and the horizontal radiation angle is 120 degrees.

The frequency response of each cell box is 50 Hz~18 kHz+3 dB, the power is 1500W, and the sensitivity is 134 dB. The high frequency unit radiates outward through the waveguide tube. This is the earliest line array product, which attracted people's attention at the beginning.

The demand of the market, the development and application of high-tech make the line array loudspeaker system become the symbolic product of each company to show its strength. Now the linear array is the combination of horn technology and array technology, which makes the radiation performance more perfect.

Characteristics of two-wire array loudspeaker system

01 Cell Box Arrangement
Line array loudspeaker system is composed of a series of cell boxes, which are arranged according to certain rules and can be arranged in a straight line and "J" shape according to the needs of sound field. The number of cell boxes is determined by the need of sound reinforcement field, but it must meet the basic requirements of forming line array.

That is, the length of the line array should be at least half of the wavelength of the radiated sound wave. The radiation characteristics of each cell box are strictly required. For example, radiated acoustic power, frequency characteristics, horizontal directivity, distortion and linear phase must meet the requirements of line array.


02 high power, long projection distance
For example, the low-frequency unit in the cell box of EAW KF761 has a power of 1200W and a sensitivity of 96dB; the medium-frequency unit has a power of 500W and a sensitivity of 107dB; and the high-frequency unit has a power of 150W and a sensitivity of 112 dB.

The radiation impedance of the loudspeaker is improved and the radiation efficiency is improved because of the interaction between the cell boxes after the cell boxes are composed of arrays. Therefore, it is easy to use linear array loudspeaker system as sound source beyond 100m in order to obtain more than 100dB sound pressure level.

The sound field covered by 03 is relatively uniform, the interference area is small and the playback resolution is high.

The vertical directivity of line arrays is very sharp, generally around 10 degrees, and the narrowest is up to 3 degrees. The radiation beam is narrow, the direct sound to the corresponding audience area is stronger, and the radiation distance is farther.

In a large area, the change of sound pressure level is relatively small. Because of the side lobe control of the line array, the overlap area of the radiated sound field is relatively small and the interference surface is small. Direct access to sound-based areas, good sense of hearing, clear voice, high resolution.


3. How does a linear array speaker work?
How line arrays work can be a rather in-depth discussion. Here, we will not explain the details of the whole theory in too much detail. Now we will use simple language and mathematical calculation to let you first understand how the sound of a typical loudspeaker is dispersed with the increase of distance.

01 Inverse Square Law
The content of the inverse square law in acoustics is that the magnitude of sound intensity and the distance between the sound source and the listening position are inversely proportional to the square. As a result, the sound pressure decreases by 6 dB for each time the distance between the listener and the point source is doubled. This is the performance of the speaker that we usually use, although there are many slight differences between practice and theory.

02 point source
The premise of the inverse square law is to assume that the loudspeaker can radiate omnidirectionally. For solid speakers, this is rare unless the speakers emit very low frequencies (which is why we always emphasize bass or ultra-bass without directivity).

However, with the increase of sound propagation distance, even the typical directional loudspeaker (such as the horn loudspeaker with 90 horizontal coverage angle and 90 vertical coverage angle) will follow.