A PA system is usually a system that amplifies the speaker's voice in real time to the listener. The speaker and the listener are usually in the same acoustic environment. A successful sound reinforcement system must have sufficient loudness (sufficient sound gain) and sufficient sharpness (low percentage of speech intelligibility loss) and can evenly cover the audience without covering the area without the listener. .
The sound reinforcement system consists of a sound reinforcement device and a sound field, mainly including the sound source and the acoustic environment surrounding it, a microphone that converts the sound into an electric signal, a device that amplifies the signal and processes the signal, a transmission line, and a speaker that converts the signal into an acoustic signal. And the acoustic environment of the audience area.
The basic principle of sound reinforcement systemCompared with ordinary home audio systems, the sound reinforcement system must ensure that the final use effect or actual test data can meet the requirements of the relevant parties, taking into account the impact of sound reinforcement on the sound quality, and require a better The method of adjusting the sound requires a basic professional sound reinforcement system to include at least program sources (microphones, also optional program player equipment), mixers, professional power amplifiers, professional speaker systems (speakers) and other professional audio equipment. ,As shown in Figure 1.
The microphone is the source of the sound system. Its quality has a great influence on the sound quality of the sound system. Therefore, it is very important to choose the correct microphone. Taking into account the "briefest" characteristics of the "basic sound reinforcement system", the microphones in the system are wired, which can make the system more practical and simple.
2, professional CD playerThe professional CD player in the basic sound reinforcement system is an optional device. Its function is basically the same as that of the civilian CD player. It is also playing music records (CD records) and is responsible for providing audio signals to the system. Compared with civilian CD players, professional CD players have higher reliability requirements, good shockproof performance, and true sound. There is no "tone dyeing" (artificial increase of sound characteristics), high signal-to-noise ratio, and low noise performance of civil CD players. It's fast for quick selection.
3, mixing consoleThe mixer is the control center of the audio system. Its function is to amplify and match the input audio signals of each channel; level control and mix the input/output signals; modify and adjust the pitch and tone of the audio signals; Control, assign, monitor, and indicate output signals. There are many types of mixing consoles, and the basic sound reinforcement system is configured with a simple compact mixer.
4, professional power amplifierA professional power amplifier converts the audio voltage signal output from a sound system such as a mixing console into a power signal that drives the speaker sound. Compared with high fidelity power amplifiers, professional power amplifiers have: large power, high performance index, flexible use, complete protection measures, and some power amplifiers also have information display and remote control functions. The configuration of the professional power amplifier is mainly based on the professional speaker to determine the size of its power, the general professional power amplifier's effective power is 1.5 to 3 times the effective power of professional speakers.
5, professional speaker systemProfessional speaker system is also called “professional speakerâ€. Its function is the same as that of high-fidelity speaker. It is to convert the audio power signal output from a professional power amplifier into a sound signal. The configuration of a professional speaker should be based on the use environment and investment conditions of the sound reinforcement system to determine its technical parameters and brand model.
The input signal of the mixer is roughly divided into two types: low-impedance microphone signal input and high-impedance line signal input. In fact, we can think of the difference between low resistance and high resistance as the difference in water pressure or water velocity. For example, if the level of the high-impedance input is high, it is as if the water pressure is high and the water flow is more urgent. It is appropriate to directly input the water to the mixing console. It is not necessary to add any link to adjust the water pressure and the water flow rate; but The level of the low-resistance input is low, as if the water pressure is very low and the water flow is very slow. It is not appropriate to directly input into the pool of the mixer. We need to add a pump in the large pool to make the water low in resistance. Pressure it to increase, so that the water flow speed up! Therefore, a dedicated circuit amplifier is built into the low-impedance input channel of the mixer to amplify the low level to a suitable level. The characteristics of water use to describe low-resistance signals and high-resistance signals should be well understood.
Only after distinguishing between high resistance and low resistance, can you choose the right wire for the appropriate connection. Basically, the console input jacks can be basically divided into 3 types:
1. TRS: The high-impedance input part usually uses a 6.35cm TRS stereo connector for balanced input. Try not to use the 6.35 TS monophonic (acoustic) connector for unbalanced input. Now we use most of the audio playback equipment such as: CD, The output signals of VCD, DVD, MD, MP3, etc., as well as most musical instruments are usually high impedance signals.
2. XLR: Low-resistance is usually balanced with an XLR connector. Nowadays, most wired microphones are usually connected to the mixer with low-resistance connectors.
3. RCA: If some mixers have TAPE recording inputs, they are usually connected using RCA Lotus connectors.
Mixer signal input part needs to pay attention to the problem: the above has been introduced in the mixer's input signal can be roughly divided into low resistance and high resistance input, but how to accurately define a certain signal is a low resistance or high resistance you need to be flexible. For example, according to the standard, electronic keyboards, electric basses, electric guitars, etc. are high-impedance signals, which can only be input to the mixer with a 6.35 plug, but in some places, the cable from the stage to the mixing console is too long. Large, plus the interference of lighting and other systems, the noise floor of this signal line is already very large. Even if no audio signal is input, when the gain of the input channel of this line is increased on the mixer, there will be A lot of noise floor.
(b) Line connection of the output section of the mixerUsually, the main output part of the mixing console still refers to the total volume output, the group volume output, and the AUX output. In general, the output of the mixer can be divided into 6 parts by function:
1. Marshalling output: If we independently control the volume of the subwoofer through the 1-2 grouping, then we can only output the audio signal from the corresponding output jack of the mixing console 1-2. Most of the outputs of the marshalling output adopt the TRS. Stereo jack for balanced output, of course, some use card slot.
2, the main channel output: LR main channel XLR card output is usually balanced, some small mixers also use the TRS stereo jack instead.
3, AUX output: Mixer AUX output is the most commonly used output to the vocal effect, followed by the band or singer to provide monitoring signals, of course, also opened for other purposes, such as: recording, used as an auxiliary speaker Signals, etc. AUX usually uses the TRS stereo jack output signal.
4.Direct direct output part: there is a “direct direct output†jack in each input channel of the professional mixer. This jack can be provided to other devices for recording, monitoring, etc. Each channel of the mixer is usually TRS stereo jack output signal. For example, a live TV station needs to be broadcast live, and live broadcasting is also required. If there are 20 audio source signals, then we can input the 20 audio source signals to the TV station's mixer first, and then use the direct output from the TV station mixer. The jack re-inputs this 20-channel source signal into the live performance mixer. Of course, for security, the 20-channel audio signal is first adjusted and distributed by the signal amplifier and then sent to the TV mixer, live mixer, backup emergency mixer, recording mixer or other. Equipment and so on.
5, recording output: general analog recording output signal jacks mostly use RCA lotus connector. If it is a digital signal, it may use other digital output methods such as optical fiber and FireWire.
6. INS plug in and out jack: This kind of jack in the mixer is between the input and the output. It uses the TRS stereo connector to connect. About the INS insertion and insertion A lot of sound engineers may not be able to use it, it can insert a peripheral device into an input channel, a group channel, or a main (left and right channel) channel of the mixer, and separate the sound signal of the inserted channel. Processing. Use the TRS three-position stereo connector to connect the signal from the head of the TRS three-way stereo plug to the input of the device to be inserted, and then send a signal from the output of this device to the TRS The ring end of the stereo plug then flows into the mixer. For example, we can use this method to insert an equalizer into the mixer's 1- and 2-channel microphones. This is equivalent to truncating the 1- and 2-channel microphones, adding a water processor (equalizer), and then inputting Mixer, so that adjust the tone better.
The above is the connection of the mixer. No matter whether it is the input part or the output part of the mixer, the socket and the signal connection method used are basically these types, but the connection must be correct.
Second, equalizer, limiter connection1. Equalizer: As we all know, the main function of the equalizer is to adjust the timbre, adjust the sound field, and suppress the acoustic feedback. Therefore, the equalizer is almost an indispensable device in the current audio system. At present, balanced input and output parts use balanced sockets. It is best to use a balanced line with XLR connectors for connection. Of course, balanced lines with TRS connectors can also be used.
2. Compressor: A compressor is a device that processes audio signals. It can compress or limit the dynamics of audio signals. In fact, the main function we now use when we use a compressor is to let it compress high-level signals so that it can protect its subordinate audio equipment. It can be said that in a complete set of audio equipment, in addition to mixing consoles and equalizers, the pressure limiter is regarded as the most important peripheral equipment, so under normal circumstances the compressor should be placed in front of the amplifier, and other peripheral equipment. Behind. The connections can be balanced using XLR connectors or TRS connectors.
Third, the electronic divider connectionThe electronic frequency divider is an audio peripheral device that can divide an audio signal of a frequency range of 20Hz-20000Hz into suitable and different frequency bands, and then respectively send them to a corresponding power amplifier to drive a corresponding speaker. The input part of the current electronic frequency divider is still relatively simple, but the output part is more complicated: there are treble output, midrange output, bass output and so on.
When connecting, the output of the bass signal and the output of the mid-high signal must not be confused. Otherwise, the high-frequency signal gives the bass speaker and the bass signal to the high-frequency speaker. In this way, the sound system may not have sound, because the frequency is not correct. , It will burn the speakers and other equipment! The electronic crossover can use the balanced line of the XLR connector or the balanced line of the TRS connector.
Fourth, feedback suppressor connectionIn terms of equipment connection, balanced lines using XLR connectors or TRS connectors are also used. The connection method can be broadly classified into the following three types:
1, as the equalizer and other peripheral devices as serially connected in the sound system, so the advantages of the connection is: connection and operation is very simple, suitable for simpler systems. However, the disadvantage is that this connection method will also affect other audio signal passing through the feedback suppressor when suppressing the microphone acoustic feedback.
2. Use the INS insert/out interface in the mixer channel to cascade the feedback suppressor in the corresponding channel. The advantage of this connection is that the feedback suppressor can be adjusted as much as possible, without regard to other influences. Sound source. The disadvantage is that using this connection method, a feedback suppressor can only control the two channels of the mixer at most, and the equipment utilization rate is too low.
3. Use the INS insert/drop interface in the mixer group to connect the feedback suppressor in series in the corresponding grouping channel. The advantage is that the microphones programmed into this group can be processed in a centralized way without affecting To other sources. In summary, because this method can fully utilize the feedback suppressor, it is also the most widely used connection method.
Fifth, the delayer connectionThe delayer can delay the audio signal and is generally used in some systems where the sound field space is large and multiple groups of speakers are required for distributed sound reinforcement. Because in this kind of system, the sound is sent out from the speakers in different positions, and it arrives at the ear of the listener when there is a sequence. Therefore, in order to ensure the consistency of the sound image, increase the readability of the sound, and avoid the turbidiness of the sound. , banding and tailing, we need to use the delayer for related processing.
About the determination of the delay object, who is the delay? In fact, it's very simple. Just figure out the following three points:
1. The first is people-oriented. Even more, no matter how good the audio equipment is for people, so in a sound field, we must first regard the audience as the benchmark.
2, the second is based on the main source, usually the main speaker and the main stage. Ideally, it should be that the sound from the main source of sound is directly transmitted to the ears of the audience and is the ideal realm. However, due to the speaker's energy, range, directivity, sound field sound pressure uniformity and other reasons, most of the indoor sound reinforcement system still needs to increase some distance from the audience.
Closer supplemental sound box.
3, the third point mainly refers to these auxiliary supplemental sound boxes that are close to the audience, that is, speakers that may require delay processing. In most cases, the first factor is determined, the second factor is determined as the main sound source, and then the third factor auxiliary sound box is processed in a delayed manner. The speed of sound is about 340 meters per second, so the delay time is calculated based on the distance between the third-factor auxiliary speaker and the first-factor main speaker. Know that the delay object can correctly connect the delay device, the connection is basically like the equalizer and other peripheral devices in series in the audio system in the signal channel needs delay, using XLR connector balance line or TRS connector balance Lines are connected.
Sixth, the exciter's connectionThe audio exciter is actually a kind of harmonic wave generator, which uses human psychoacoustic characteristics to modify and beautify the sound signal.
Actuators generally have the following three methods of connection:
1. It can be cascaded into the signal channels that need to be stimulated in the sound system like peripherals such as equalizers. For example, in a mixing console, 1-2 groups are vocals, if you want to motivate this grouped vocal The exciter can be connected to the 1-2 grouping channel of the mixing console using the plug-in/out interface.
2. If you want to perform comprehensive processing, it is sufficient to connect an exciter in the output channel of the mixer's master volume output channel or other grouping output channels.
3, the exciter can also send out the signal from the AUX like an effector, and then return to the mixer, so that it can adjust which channels need to carry out the excitation processing, how much force needs to be handled, and so on, which is actually more flexible. The exciter is also connected with a balance line using an XLR connector or a balanced line with a TRS connector for signal connection.
Seventh, the digital effect processor's connectionThe effect device is a sound peripheral device that processes and manufactures various sound field effects, and is generally used for processing vocal sounds. In most sound systems, if the human voice is not processed by an effect processor, it will become full and full of brightness. That is: There is no moisture in cognac.
The latest effects processors now use digital processing chips, so we also call them digital effects. The effect is less like the equalizer and other peripheral devices connected in series in the sound system, under normal circumstances are from the mixer's AUX send signal to the effect of the input interface, and then return to the signal from the output interface of the processor In the sound table. In terms of signal connection, most of them use TRS connectors to connect with balanced circuits. Some professional effect processors also use balanced lines using XLR connectors.
Eight, amplifier and speaker connectionAll of us should be familiar with this, but we must pay special attention to it: In the signal, the signal line of the amplifier should be balanced as much as possible so as to minimize noise. Many sound engineers like to supply one or two signal lines to multiple amplifiers. However, if there are more than four amplifiers, it is advisable to use a signal amplifier to separate out a sufficient number of unattenuated signal lines for each amplifier to use. This can reduce system noise, reduce hidden dangers, and improve signal-to-noise ratio. In terms of power transmission, try to use thicker and shorter speaker cables and use reasonable cabling to shorten the speaker cable distance. Then pay attention to the positive and negative electrodes to avoid short circuits.
1, pay attention to the power: audio equipment must have a dedicated power supply, and the power of the light is separated, and the light like a lower voltage, but the sound will have a standard voltage. With a dedicated power supply, a stable and reliable power outlet is also required. The "power supply sequencer" can be used as much as possible. Although the cost increases, stability and ease of use increase. In short: It is crucial to properly and securely connect the power of all audio equipment. Another point to note: some imported equipment will have a 110V and 220V selector switch in the power section. In our country, we must make sure that we can choose to connect to the power at 220V.
2. Pay attention to the grounding of the equipment: It is very important to properly connect all audio equipments to a good ground wire. A good grounding can reduce the interference of signal transmission of the equipment and improve the stability of the equipment. It should be noted that the grounding wire should be made in accordance with the grounding standard of the lightning protection line, that is, the conductor buried in the underground part should be rust-proof, contact better, and buried deeper, and it must not be shared with the grounding wire of the three-phase power line. Not only does it reduce the noise in the sound system, it also easily damages the equipment.
3, pay attention to select the appropriate connection signal line: a sound equipment, we can use the XLR card to balance the line to connect, do not use TRS balanced line connection; can use TRS balanced line connection, do not use TS mono unbalanced There is no way to use TS mono unbalanced line connection equipment.
4, pay attention to the signal inversion and short circuit: the signal line short circuit often cause silent failure, check it up is very troublesome, unless a signal line removed with a multimeter to detect the job, so be careful when welding the line.
5, pay attention to the length of the signal line: When connecting the device, we should try to use shorter signal lines, one to save costs, and second, to reduce the line resistance and interference. Under normal circumstances, the signal line with balanced transmission can reach up to 300 meters, while the non-balance line can not be transmitted over long distances.
6. Pay attention to the level of the device: If the +4 and -10 or -20 level switches are switched on the rear panel of the device, we will normally place it at the +4 position. This is the standard level.
7. Pay attention to the pass-through: Many devices have a Bypass button. When the pass-through, the device generally does not work, so we have to pay attention to check this button, or if we let the limiter through does not work, then The device behind the compressor will lose its protective effect.
8, be careful of misuse: due to more equipment, more buttons, it is often prone to misuse, such as: There are some electronic crossover on a "× 10" button, we take care not to press it easily. For example, when our crossover point is adjusted to 200Hz, pressing this button 200 × 10 becomes 2000Hz, so we must avoid misoperation.
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