Discussion on line array loudspeaker and its indoor application

1 Introduction

    Because the line array loudspeaker with a horizontal uniform coverage, vertical point to strong, radiation energy attenuation small number of very useful features, in many fields of sound reinforcement is gradually replacing the traditional loudspeaker array. For in the same place with the same volume of sound reinforcement, line array loudspeaker system may be smaller, lighter, and more easily lifting. Line array loudspeaker can venues with the specific shape, the appropriate hung, aimed and bending, can provide good quality of most of the audience. The speakers of the line array are introduced, the design principle, the combination mode and the structure of the driving unit are different. In this paper, the author analyzes the typical brand of line array speakers from the perspective of waveguide design.

    2 Line array speaker

    2.1 Line array is not a line sound source

    The line sound source is composed of a series of equal distance drivers. The initial application prototype generated in the fifties of the 19th century and was originally designed in order to improve the speech intelligibility in the halls of reverberation. The use of linear sound source is based on the very small vertical direction angle. If the vertical direction is 0 degrees, this is what we say cylindrical wave. When the sound source distance increases, the energy of a cylindrical wave will attenuate 3dB, however, the sound source distance is increased by one time the spherical wave the energy will be attenuated by 6dB[1].

    however, there are two necessary conditions for the composition of the source of the sound source: 1. The linear length is 4 times more than the radiation wavelength, which can ensure that the direction of the wave is close to the plane wave in the vertical direction. 2, in contrast to the last condition, the distance between the center of the adjacent speaker unit is less than half wavelength. Olsoni in 1840s, the radiation pattern of the adjacent phase with two less than 1/4 wavelength is calculated. Between the 1/4 and the wavelength of 1/2 is not the side lobe (i.e., the maximum value of the interference. The interference waveform is usually caused by destructive interference), and this phenomenon will continue until the spacing is greater than 1/2 wavelength.

    This means that only a very long line array can be used to meet the working principle of the linear sound source in the practical application. In real application, most line array is in line with the principle of the line sound source is not more than a frequency doubling. So the line array can hardly be considered as the source of the sound.

    2.2 Practical work of line array

    The excellent capability of a line array is that it can provide uniform sound pressure from the front row to the back row from the front row to the back row. The sound pressure level from the back row to the front row is almost the same. To see why, let's review some conventional horns and a compressed drive design of sound system example. Horizontal array used in speaker in the design will be the spherical radiation waveform compression is pie shaped, such as 60 to X40 degrees, 90 degrees to X40 degrees or other similar design the provide good coverage of site amplification. If the area of a small area of the directional cover can be aligned to the final row of the speaker's radiation spindles, the 6dB attenuation angle is aligned in the front row to get a uniform sound pressure cover. If hang point high enough, you can through the position and angle of the loudspeaker is fixed, the distance of the first row to the trumpet is half of the distance of the last row into the horn. At this time, the horn of the radiation angle of discrete control ability can very good balance it all front to rear field uniform SPL and effect.

    If architects to build public places is widely suitable for the radiation characteristics of the horn, and region is sufficiently small enough, then a speaker can cover each side of the audience, so we don't need a line array. Of course, it is not possible to determine the size and shape of the field. Line array than ordinary single speaker sound pressure output more than 18 to 24dB, and the vertically pointing can be by way of curved arrays to suit different site amplification. Just like the properly fixed traditional horn type loudspeaker position and angle, correctly curved line array can release the same acoustic power of equal areas of the audience. This means that when you are close to the array, the radiation angle of each speaker module should be greater, so the distance between the array from the upper to the lower box should be gradually increased. So, for most sites, the array is generally similar to the sound pressure in the back row to the back row, the shape of the array is generally similar to.