Line Array

The term refers to a concept of line array sound systems that are used for concerts and other live events. It is a speaker system for streaming music or voice over long distances, ie for example the auditorium of a large concert.

Basics

A distinction between conventional PA systems, where multiple speakers in a horizontal plane - are stacked to sound for a certain area sufficiently, and the line array systems that supply the auditorium with sound with superimposed speakers - ie next to each other.

Basic reality of a sound situation is to provide a spatially limited area with sound. This will supply all points in space with the same signal to a sufficient level, ideally with a linear frequency response and linear phase behavior without interference. In order to obtain sufficient level, a single speaker per side of the stage (stereo sound ) in most cases is not sufficient. When combining multiple speakers to areas of overlap ( interference ) that lead to dips in the frequency image, and thus result in poor sound. The reason for this is that identical sound waves transmitted by at least two different points ( speakers) of. Depending on the phase this in turn leads to cancellation at certain frequencies, in other amplifications. The result is a bent frequency response and thus unsatisfactory sound.

Technology

To address this problem, you went with the technology of line arrays is another way: These work on the principle of a line shaft with finite length. Each element in the horizontal plane a clearly defined beam angle of usually 70 to 120 degrees, which is sufficient to cover the entire auditorium of two points of view - to provide - without side by side speakers. In the vertical plane the radiation is isophasisch, that is, that all are directed frequencies to be transmitted in phase in one direction only. If several such elements one above the other groups, the result is in the vertical coherent wavefront that has virtually no interference, since each point in the space of only one speaker per (stereo ) page is sonicated.

With this technology it is possible without any problems to sonicate from the stage of a full auditorium with several thousand people, since every element of the speaker line array in the distance has the strong focusing of the sound a much higher sound pressure levels.

The commonly used term of the cylindrical wave is a pure marketing term.

Speaker Systems

To establish speaker elements with the emission of a line shaft, some technical and physical obstacles to overcome. In the horizontal direction of radiation to achieve a defined angle over the entire frequency spectrum, is unproblematic. This is done, as with conventional systems PA by the use of horns with respective opening angles and bends of the individual paths.

The claim to the vertical dispersion to produce a isophasische wavefront is far more difficult to implement. In the treble, there are different approaches to. All have in common is the use of so-called wave - guides. This is to horns, to which a conventional compression driver is connected and its phase noise comes out of the horn aperture.

The French company L- ACOUSTICS is a pioneer in the field of modern line - array technology. My 1992 with the V- DOSC system have placed on the market, the world's first working line source array operates with a horn placed in the interior phase plug and waveguide, which is used to redirect the sound of different wavelengths. This waveguide is protected by worldwide patents. The V- DOSC system is virtually unchanged in use since 1992 and is widely recognized as the industry standard in the field of line array systems. In the procedure of the manufacturer JBL Professional this is done by a long sewers of sound with different length paths for the different wavelengths. Until the horn aperture, finally, the time differences are balanced and the sound comes as a coherent wave front to the outside. Another route you go with the manufacturer NEXO. Here radiates an ordinary HF driver his sound on a parabolic reflector in phase aligning the different wavelengths by its curvature.

Result under all approaches is a coherent wavefront for the high frequency range. The midrange stacked speakers have the ability to bundle their sound due to the longer waves. This makes you look at line arrays utilized by the midrange driver are mounted above each other in every single element. When stacking the entire array so are ultimately the drivers of all the elements in a vertical line and thus function as a line source.

This applies in the vertical plane tends to be for the low frequency range, but the lower frequencies are due to the narrow design of the speakers around bent to the array and radiated more spherical, at least in the horizontal direction.

Regarding the transmission of Subbassbereiches there are between line array sound system and conventional no difference. For this still -working or horn-loaded bass reflex principle after the basses are used with large low-frequency drivers. These are available as usual in front or to the side of the stage, but can be arranged by some manufacturers in the line array.

Use

In order to fill a whole room, it is not enough simply the elements of a line array just to stack one above the other. Since the line-like directional behavior of the speaker from a certain distance is still wider to overlap areas would thereby form again. A further disadvantage would be the concentration of the total power to a relatively low beschallbaren space. To counteract these factors and to make use of the fact the line array is hung in an elevated position ( flown ) and curved array ( gecurved ). The individual transverse elements are connected firmly but anwinkelbar at their front corners. At the rear corners of the trapezoid body care in a number of grid points usable connectors to each other for the right angle of the speakers. Applying this technique, for example, eight contiguous elements, we obtain a curved array of loudspeakers ( "banana" ).

Benefits

The advantages in coverage of the entire array are therefore especially in the interference freedom and uniform sound pressure distribution over the whole auditorium. This is achieved by selective and controlled dispersion of sound and precise interaction of the individual elements. From this arises, however also a disadvantage: In order to use the system correctly and effectively, it requires careful planning. The system engineer needs to obtain information about the geometry and nature of the space to be sonicated. Here, the user has computer simulations to the side without the accurate calculation of the site, the right height and angle and the number and type of speakers would be very complicated and time consuming. These programs are provided by the manufacturers of the line array systems are available in the rule and are tailored to these.

The high range of this type of sound can easily see that line arrays are not suitable for small rooms. Here would be expected with strong reflections from the rear wall, which would counteract the avoidance of interference.

Have a big advantage in terms of handling line arrays over conventional systems. In contrast to these, there is a line array by design of many small elements that make considerably easier assembly and disassembly as well as transport and exchange.

Swell

• Volker Holt Meyer: Mystery Line Array - fashion or trend? March 5, 2003 (PDF file, 2 MB).
• John Meyer: " Can Line Arrays shape Cylindrical Waves A Line Array Theory Q & A? " 2005