Line array, do you know
In recent years, the linear array speakers system has been widely used in large -scale soundproof places with its unique advantages. The linear array speakers system is produced by market demand and is also a product of high -tech, so it has attracted much attention.
Several line array speakers
1. The generation of line array speakers system
In the 1960s and 1970s, rock music represented by the “Beatles” band in Europe and the United States has emerged. There are hundreds of thousands of audiences in the square to watch rock concerts. Sound expansion is a big problem.
For example, 600,000 people participated in a rock concert in New Jersey in the UK on September 3, 1977. The soundplacement system uses multiple speakers and placed “sound tower” together, and the installation and commissioning are very troublesome.
After careful design and debugging, it took a lot of energy, and the sound expansion effect was always unsatisfactory. This phenomenon provides a market information that requires large -scale sound -expansion systems with large power and convenient installation and commissioning.
Some large companies see market demand and are committed to developing high -power and long -projected soundplay systems. From the perspective of acoustics, there are two methods that can obtain the effect of high -power and long projection.
01 One is a tube
The sound energy is radiated in one direction through the number of the tube, controlling the directionality, improving the radiation efficiency, and achieving the effect of long projection. For example, in the 1950s, we used a large tube to the radio system of Kinmen and Matsu, with a tube of more than ten meters long and a few kilometers of communication. The research of the tube has successfully developed the constant -naming tube speaker, the number of the multi -drive units, etc.
02 Another is the speaker array
The speaker array proposed in the 1930s uses the principle of interference to control the directionality. In fact, a pillar -type speaker was popular at that time. The sound columns have a relatively narrow vertical direction, but the power is not large enough, the projection is not far, and the dynamics and frequency width of the sound still have some problems that need to be overcome. Some big companies have their own focus according to their own situation.
French L-ACOUSTICS first launched the V-DOSC system in 1993. It is a array consisting of a column of a unit speaker. The working principle is similar to the sound column. Its vertical direction can be controlled, determined by the number of unit boxes, and the horizontal radiation angle is 120 °.
The frequency sound of each unit box is 50Hz to 18KHz ± 3DB, the power is 1500W, and the sensitivity is 134DB. High -frequency unit radiates outward through waveguide. This is the earliest launch of line array products, which attracted people’s attention from the beginning.
The development and application of market demand and the development and application of high -tech make the line array speaker system become the iconic products that show their strength in each company. The line array is now a combination of number tube technology and array technology, making the radiation performance more perfect.
Features of the second -line array speaker system
01 Unit Box Rules Arrangement
The linear array speakers system is composed of a column of a unit box. These unit boxes are arranged according to certain rules. According to the needs of the sound field, it can be arranged in a straight line and the “J” shape. The number of unit boxes is determined by the needs of the soundproofing field, but it must meet the basic requirements of the formation of the line array;
That is, the length of the line array should be at least half of the wavelength of the radiation sound wave. The radiation characteristics of each unit box have strict requirements. For example, radiation sound power, frequency characteristics, horizontal directionality, distortion and linear phase must meet the requirements of the line array for it.
02 Power and long projection distance
For example, the low -frequency unit in the unit box of EAW KF761 is supported by 1200W and a sensitivity of 96DB; the mid -frequency unit power is 500W, the sensitivity is 107DB; the high -frequency unit power is 150W, the sensitivity is 112DB.
After the unit box forms array, due to the interaction between the unit box, the radiation impedance of the speaker has been improved and the radiation efficiency is improved. Therefore, it is easy to use the line array speakers system as a sound source to get more than 100DB outside of 100M.
03 The sound field covered with is relatively uniform, the interference area is small, and the resolution of the replacement is high
The vertical direction of the line array is very sharp, generally about 10 °, and the narrowest ones can reach 3 °. The sound bundle of radiation is narrow, and the direct sound of the corresponding audience area is relatively strong, and the distance of the radiation is relatively long;
The changes in sound pressure levels in a large area are relatively small. Due to the side petal control of the line array, the overlapping area of the radiation sound field is relatively small and the interference surface is small. Direct sound -based areas, good hearing, clear sound, and high resolution.
3. How does linear array speakers work?
How to work in line arrays can be a considerable discussion. Here, we will not explain the details of the entire theory too much. The following will be calculated with simple language and mathematics, so that everyone can first understand how the sound of typical speakers disperse with the distance.
01 anti -square law
The content of the anti -square law in the acoustic science is that the distance between the sound strength and the distance between the listening position and the sound source are square inverse. As a result, the distance between the speaker distance of the sound source is doubled, and the sound pressure is attenuated by 6DB. This is the performance of the speakers we usually use, although there are many slight differences in actual and theory.
02 sound source
The premise of anti -square law is assuming that the speaker can radiate omnidirectional. For physical speakers, this situation is rare, unless the speaker emits a very low frequency (which is why we have always emphasized that the bass or super bass has no direction).
However, with the increase of sound transmission distance, even the typical orientation speakers (such as the node speakers with a 90 ° horizontal coverage angle and 90 ° vertical coverage angle) will follow the anti -square law law. Sound diffusion (that is, omnidirectional radiation).
03 line sound source
The sound pressure cover of the linear array speaker is close to the so -called wire sound source theory. Whenever the sound distance is doubled, the level will not drop 6DB. In theory, it will only drop 3DB, but in practical applications, the result is not so ideal.
Regarding why there are these differences, this article will not be discussed in detail. But even so, compared to the sound source speaker, linear array speakers have unique advantages in vertical coverage angle.
The speakers with linear sound source radiation can achieve the following effects: You can feel a relatively large sound pressure level in the rear area of the lobby or outdoor space, and in order to do this, you don’t need to operate the ordinary sound source speaker like an ordinary sound source speaker. Similarly, it deliberately increases its power so that people who are closer to the PA system to hear too loud sounds. Its advantage is that the sound of sound vertical diffusion angle is complex and varied.
So how to achieve linear sound source radiation? The answer is phase offset.
The phase offset is usually one of the things that engineers are trying to avoid in the audio system, but it can provide a central role in providing a narrow vertical coverage angle when working together to work together.
Even if the high -level speaker box design is used to shape the vertical coverage, there are still many actual overlap between the speakers in the online array. In other words, the vertical coverage angle of the line array speakers is not formed by a single speaker. It is the result of an effective interference at the exit of multiple speakers.
However, in reality, the distance between each line array speaker and the audience will be slightly different, which will cause a small degree of phase offset. Of course, you can also perform manual intervention on the vertical coverage of the line array speakers by introducing electronic delay, and make fine adjustments (EAW Anya and Anna systems apply this technology).
Precautions used by the 04 line array system
Although the application phase offsets the effect of narrowing the vertical coverage angle in the online array, their horizontal coverage angle is not affected. Therefore, a single speaker in the line array in reality can have a 90 ° horizontal coverage angle, while vertical coverage is performed vertically at an angle of only 20 ° or smaller.
In addition, even if the phase offsets the distribution of line sources and significantly improves long -distance coverage, as the distance increases, the line array will begin to present the characteristics of point sources, and yield to the anti -square fixed law distance of each decay of 6dB of 6dB. Essence
The line array has the ability to be close to the line source function, but there are some limitation and matters that need attention. First of all, the length of the array determines the minimum frequency of the coverage characteristics of line sound source.
This is because as the wavelength becomes longer, at the listening position, the sound of the relative time between the sound of the sound from different speaker units must be greater in order to achieve the effect of linear sound source.
This requires a larger array length. At the other end of the spectrum, the wavelength has become so short that the driver is too large but cannot be placed together nearly, so the relative phase difference becomes too large and cannot achieve the line source function.
In these cases, major manufacturers will use the waveguide structure to realize the conversion from the sound source to the line sound source function. Although all waveguide structures are to achieve the same purpose, almost each manufacturer uses different structures, and has its own patent to protect its intellectual property rights. This is also the most difficult link in the process of developing linear array speakers.
The line array is very useful in challenging space, because you can control their vertical diffusion and reduce sound reflection.
It is a good start to find a way to make the coverage area of the sound leave the ceiling and floor, and then choose a speaker with a specific horizontal coverage angle, which will help you keep the excess sound away from the side wall, so as to get a better indoor sound expansion definition definition Essence
Large -scale line array covered at the U2 2015 World Tour concert site (photo provided: ROYER LABS)
The form of the 05 line array
Because the vertical radiation of each speaker is very narrow, it can effectively divide the listening space into multiple parts of the past to the back. The front is covered by a small amount of speakers, and more speakers can cover the rear.
Based on this idea, a very popular J -shaped line array has been formed, which often appears in the concert hall and outdoor venues.
The exact installation shape of the line array will change according to the layout and size of the area covered by needed. Under normal circumstances, the front row covers only requires a small number of small amounts to meet the sound pressure requirements because of close distance, but because the installation angle between the uniformly covered factor line array also needs to be designed relatively.
Due to the distance from the middle and rear, more number of speakers need to be installed in concentrated angle, so as to achieve the effect of long -distance coverage. The approximate summary of this approach just now helps improve the consistency of overall coverage.
In recent years, it has also developed the way that users can adjust the power of each speaker box to make fine energy distribution adjustments -this technology is usually called power gradient.
06 miniature line array
Although line array technology is most common in professional large-scale indoor and outdoor sound expansion applications, many companies, such as Bose, Fishman, Turbosound, etc., provide small personal PA systems, use small speakers miniature array (usually 2 “-4” -4 “-4” “-4” The size) to produce the same line source coverage effect. The correct use of these systems allows them to provide good coverage in small venues.
The challenge and limitations of the 07 line array
Although the line array can help solve certain space problems, they have complicated restrictions. In addition to the challenge of controlling sufficient length to control the coverage of a lower frequency, the line array may sometimes suffer strange abnormalities. For example, some frequencies may form wave petals in the front and below of the array.
And if this happens in a bad acoustic space, it may bring serious consequences. For example, if your vocal microphone is placed below the online array, you may encounter feedback.
In addition, in terms of sound quality, even in the best case, the line array cannot be comparable to the purity of the sound emitted by a high -quality single -wheel drive speaker or a single two -point frequency drive speaker.
That’s why they are unlikely to appear in smaller spaces. In the small occasion, the number of speakers that can speak can be more appropriate if the number of speakers can be less. Of course, cost and space are also considered factors