Brief Analysis of the Composition and Development of Theater Digital Audio System

With the rapid development of China's economy and the great improvement of its overall national strength, the people's demand for spiritual culture is also increasing. Cultural life has become an indispensable part of the lives of ordinary people. Against this background, various platforms that meet the needs of spiritual culture have been further developed. Theater is naturally one of them. This article will introduce the composition of theater Digital Audio system and its transmission network.

1. Composition of typical theater Audio System and functions of each part

A typical theater audio system should include sound source, mixer, peripheral equipment, signal processing equipment, power amplifier, speaker and transmission system, as shown in Figure 1. According to the characteristics of the theater, it is generally divided into auditorium sound reinforcement system, stage return monitoring system, effect sound reinforcement system, control room monitoring and monitoring system, peripheral electro-acoustic processing auxiliary system, sound pickup and sound source playback system.

Figure 1 The composition of theater audio system

A large-scale theater audio system mainly includes the auditorium, the sound restoration system of the stage part, the monitoring and monitoring system of the control room, and the audio-visual recording and storage system. The stage part includes the pickup and transmission of sounds when the actors perform, and the stage return monitoring system to help the actors grasp the effects of the performance.

The audio system generally picks up various sounds on the scene through the microphone set on the stage, converts it into a current signal, and sends it to the audio system center control equipment through the transmission cable: through the mixing console (also known as the mixing console), the various inputs Match, amplify, mix, tune and distribute sound source signals.

The control of electroacoustic system includes two aspects. On the one hand, it is the processing of sound quality, such as equalizer, exciter, effector, noise reducer, etc. On the other hand, it is the control of the signal, such as compressor, divider, frequency divider, Speaker processor, etc.

The peripheral processing equipment processes and polishes various program signals, makes up for the defects of architectural acoustics, compensates for the lack of performance of electro-acoustic equipment, and produces special sound effects.

Signal processing equipment is an important part of theater audio system, and also a key equipment for system debugging. The traditional signal processing method is to interconnect a variety of processing equipment with different functions and different purposes with many special cables and equipment such as mixers and power amplifiers to form a sound reinforcement system. The modern signal processing method is to use a dedicated high-precision floating-point arithmetic DSP processing chip in a device, supplemented by various efficient audio data algorithms that can replace traditional equalizers, exciters, effects, noise reducers, etc. Work with multiple devices. Functions like multiple devices are all integrated on one device, and the signals before and after processing are all digitized.

As the name implies, the power amplifier is a "power amplifier". Its function is to amplify the low-level audio signals sent by the mixer and peripheral equipment (signal processing equipment), so that its output power is sufficient to drive the matched speaker load. The traditional power amplifier is an analog power amplifier, that is, linearly amplify the continuously changing audio signal (analog signal). Modern power amplifiers have also transitioned to digital networking. The overload capacity of digital power amplifiers is much higher than analog power amplifiers, and no crossover distortion will occur. Because digital power amplifiers use digital signal amplification to make the output signal and input signal phase exactly the same, phase shift Is zero, so the sound image localization is accurate. The internal resistance of the power amplifier tube in the traditional analog power amplifier is large, so when matching speakers of different resistances, the working state of the analog power amplifier circuit will be affected by the size of the load (speaker). The internal resistance of the digital power amplifier does not exceed 0.2Ω (the internal resistance of the switch tube plus the internal resistance of the filter), and the resistance value (4-8Ω) relative to the load (speaker) is completely negligible, so there is no matching problem with the speaker.

The speaker (speaker) is a converter that converts electrical energy into sound energy. The theater audio system hopes to restore the sound in the range of 20 to 20 kHz, and currently any kind of speaker is difficult to meet the needs of broadband sound reproduction. Because playing bass requires a heavy, large, and thick cone of paper cones, while playing treble requires a light, thin diaphragm, the Speaker System for reproducing the full range is generally composed of three different types of speakers: treble, midrange, and bass The unit is composed of a system.

Generally, the sound field system of the auditorium in the auditorium area of ​​the theater is divided into sound bridge speakers, speakers on both sides of the stage frame, table lip speakers, fill speakers, effect speakers, etc. The sound bridge speakers are usually arranged in three groups from left to right. The speakers on both sides of the frame are used to cover the auditorium and lower the sound image position, so that the audience feels that the sound is not coming from the high position of the sound bridge but from the stage of. The lip speakers are used to supplement the center area of ​​the front 3 rows of the auditorium and lower the sound image position. For the shielding part of the upper auditorium to the lower auditorium and the main speakers with poor coverage of the auditorium areas on both sides, it is necessary to install supplementary speakers. Effects sound speakers produce some special effects, such as surround effects, sky effects, etc.

Considering that the theater sound reinforcement system usually sets up multiple tuning positions, individual performances may also need to be recorded or relayed. The pickup signal cannot be sent to the main control room only, but multi-channel signal distribution is required. The usual design method is to set up a technical room near the stage. The pickup signals of the stage, orchestra, lighting bridge and other places are first collected here, after being distributed by the special distribution system, and then sent to the above tuning stations or TV broadcasts respectively. Special interface.

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