Joke Collection Website - Mood Talk - How a stage sound engineer plays a piece of music quickly in a show
How a stage sound engineer plays a piece of music quickly in a show
Signal input of the mixer: The input signal of the mixer is generally divided into two types: low-impedance microphone signal input and high-impedance line signal input. Each input can be regarded as a water pipe. That is, if a mixer has multiple signal inputs, it is like the water from multiple water pipes flows to the mixer for processing. We can think of the difference between low resistance and high resistance as the difference in water pressure or water flow speed. For example: if the level of the high-impedance input is high, it is like the water pressure is very high and the water flow is fast. It is suitable to directly input it into the pool of the mixer. There is no need to add any links in the middle to adjust the water pressure and water flow rate; but The level of the low-impedance input is low, just like the water pressure is very low and the water flow is very slow. It is not suitable to directly input it into the pool of the mixer. We need to add a water pump to the large pool to pump the low-resistance water. The pressure is increased to speed up the water flow, so the low-impedance input channel of the mixer has a built-in special circuit amplifier to amplify the low level to an appropriate level. It should be easy for everyone to understand how to use the characteristics of water to describe low-impedance signals and high-impedance signals.
2: Adjustment of the mixer channel gain: To input the sound source into the mixer, we must first distinguish whether it is low impedance or high impedance, and then use a standard signal line to correctly connect it to the mixer. On the sound stage. If we want every sound source to achieve perfect sound quality, we need to make careful adjustments. The gain of each input channel of the mixer is very important and critical, but many sound engineers seem to simply regard the gain as a volume knob, which is a big mistake. In fact, gain is mainly used to control the dynamic range of the input signal. Generally, when the gain is adjusted to the maximum without distortion, it is the maximum effective dynamic range and the best effect. It’s difficult to understand this way, let’s describe it with water: the input channels and input lines of the mixer will have a basic background noise. This background noise is like the sediment in the bottom of the river and cannot be eliminated. As we all know, when the river is not deep, the flowing water is covered with mud and sand, and the water quality is definitely not good. So in other words, if the dynamic range of the gain adjustment is insufficient, the sound source signal will be like running water under the mud and sand, and the background noise will emerge, and the sound quality will definitely be bad at this time; on the contrary, when the river water is relatively deep, The flowing water is relatively clear, and the water quality must be very good, which means that the dynamic range of the gain adjustment is larger and more reasonable, so the sound quality must be very good; of course, if the water is so powerful that even the dams are broken down, the bottom of the river is damaged. If it is overturned, it means that the level signal is so loud that it is distorted. At this time, there is no sound quality, and it will also cause damage to the equipment. Therefore, the bigger the gain, the better. It must be appropriate and appropriate. I think even audio beginners should be able to understand the function of gain in this way. :
3: Adjustment of the mixer channel equalization group: After the gain is adjusted, the next step is usually to adjust the mixer channel equalization group. The order of adjustment should be to adjust the bass part first. Start, and then adjust the mid-range and treble parts. Because only by ensuring the basic tone of the sound can the multiple overtones of a good sound be guaranteed. Basic adjustments are ok for everyone, here I will just talk about a few technical aspects. Nowadays, the equalization groups of professional mixers generally have frequency selection adjustments. Many sound engineers do not know how to use them flexibly. It is difficult to explain them all in detail. Some things depend on personal understanding, so I can only briefly explain: For example When playing disco music, we feel that the bass strength is not enough. We can select the bass frequency of the equalization group of the channel where the disco music is located to be around 200Hz, and then use the adjustment knob to increase it moderately, so that the bass strength comes out; For example, when a female singer's sibilance is obviously very prominent, we can select the high-frequency frequency to be around 6000Hz, and then use the adjustment knob to moderately attenuate the sibilance, which will appropriately reduce the sibilance. If you use it flexibly, you can also use the frequency selection function of the equalization group to suppress acoustic feedback. For example, generally there will be a vibration peak around 300Hz in a dance hall. This frequency is often prone to acoustic feedback. We can input the microphone to the frequency of the channel. Choose around 300Hz, and then use the adjustment knob to perform moderate attenuation, so that you can effectively reduce acoustic feedback. Of course, the frequency at which sound feedback is generated in each sound field is different, but no matter what frequency the sound feedback is, it can be simply controlled using this method. Of course, this needs to be flexibly controlled based on experience.
Moreover, to perfectly adjust the sound field and avoid acoustic feedback, you need to use a professional multi-band equalizer or feedback suppressor, which will be introduced in detail in future articles on peripheral systems. In short, in a mixer, what the sound engineer often needs to adjust is the equalization group of the mixer. It is often seen that some sound engineers only know how to push and pull the volume fader, and are too lazy or ignorant to adjust the balance knob. In fact, during use, it can be said that we need to adjust the mixer every moment. Take a song as an example: when the singer walks to the stage to introduce his performance, we need to turn down the bass of the microphone and adjust the reverb to moderate or turn it off, so as to ensure the clarity of the language; when the music starts, the singer starts singing When singing, we need to increase the bass of the microphone, otherwise the sound will appear thin, and at the same time increase the reverberation volume to an appropriate level; in addition, in order to prevent the treble of the music from overtaking the treble of the microphone when singing, we can slightly attenuate the treble of the music; but when the song During the interlude, the audience's attention will shift from the singer to the music, so at this time we need to increase the treble of the music and at the same time turn the music louder, so that the music will be well and naturally highlighted. , otherwise it will appear too rigid without changes. And at this time, we also need to turn down the reverberation volume, so that even if the singer suddenly speaks during the interlude, there will not be a lot of reverberation sound; when the interlude of the song is over and the next part of singing starts, we have to turn off the reverberation volume. Small music, attenuate music treble, push up microphone and reverb volume. When we reach the climax of the final singing, we also need to turn up the microphone volume, and then turn up the music volume from low to high in an instant to create a perfect, shocking, and majestic climax effect at the end. Of course, not all songs are suitable. With this kind of operation, being a sound engineer requires flexibility. I feel that if we really want to express every function of the mixer in writing, we may need to write a thick book, and the effect may not be obvious. Our space here is limited, so I will just give you some ideas and talk about my experience over the years. This is just my experience of using the mixer, and the specific aspects also depend on personal efforts and learning.
4: Adjustment of the mixer channel AUX; the various adjustment knobs on the mixer are generally the equalization group, followed by the AUX knob, which is termed: auxiliary send control. Because it is of an auxiliary nature, many sound engineers do not pay enough attention to it and do not fully understand its functions. I remember that when I was studying at the Beijing Radio and Television Department in 1997, the teacher talked about this AUX for two days, but many students were still confused. In the end, I couldn't help it anymore, and spent two minutes to solve their two-day confusion. After understanding it, many students lamented that AUX was so simple! Of course, I can’t say that my level was higher than that of the teacher at that time, but I used a vivid metaphor: I said that in fact, each input channel of the mixer is like a large water pipe. After the water comes in, it is basically divided into A, Two main water pipes B: One A-way main water pipe is: the volume fader of the channel of the mixer, which is sent out through grouping, etc. Everyone knows the channel volume fader; the other B-way main water pipe is: AUX The difference is that the AUX part in a mixer can be divided into multiple channels. If a mixer has 4 AUX channels, it is like dividing the B road main water pipe of the AUX group into 4 small tap water channels. The tube then flows out. It has the same principle as the fader below, except that the volume switch of most AUX is controlled by a knob, while the channel volume switch of the same channel is controlled by a fader, just like a big water pipe. Even though it is divided into two main water pipes, A and B, and there are many small water pipes below them, the quality of the water flowing out is still the same. So we can't just look at the superficial differences of things. In fact, their functions are similar. Seeing this, most audio beginners may be able to understand it. The most important thing is to understand that the AUX knob actually has the same function as the volume fader of the mixer. Next, let’s talk about the specific use of the AUX group: Generally, AUX is most used to connect to external vocal effectors. We use the corresponding AUX switch to send the sound that needs to be processed to the effector, and then flow it back after processing. Go to the tuner. This is basic knowledge, and most sound engineers should know it; the AUX of a large mixer usually has a pre-fader/post-fader switch. When it is set before the fader, the master volume fader under the channel has no effect. It controls the volume of this AUX; on the contrary, it is controlled by the overall volume of this channel. Other functions of AUX are for monitoring or recording.
Another convenient use is that we can also use AUX to control the bass volume of a sound system, so that channels that need more bass can turn up the corresponding AUX, without requiring sound sources with large bass volumes, such as microphones, etc., where they are The corresponding AUX can be turned up less, otherwise bass feedback will easily occur. Generally speaking, if you understand the principles of AUX, you can draw inferences about other cases, so I won’t go into details here.
5: Adjust the sound and image balance of the mixer: Generally, sound engineers understand the sound and image of the mixer, but many of them have a rigid understanding. For example, a two-channel stereo music signal is input to the mixer. On the sound console, most sound engineers will turn the panning knobs of these two channels all the way to the left and right, thinking that this is "stereo sound". In fact, in this case, the sound coming out of these two channels will appear very floating, with a faint sound in the middle. , weak; if you turn the panning knob to the middle, you will feel that the music sound is on your head, which is uncomfortable, and the width of the sound is not enough; the best position is to turn the panning knob of the left channel to 9 o'clock on the clock Position, the panning knob of the right channel is turned to the 15 o'clock position of the clock. This way the music will not drift but has a wide dynamic range, good strength and penetration. You can try it carefully. I won’t analyze the principles. I only focus on practice. I won’t go into other aspects of audio and video applications, they are all basic knowledge. In fact, things that are often thought to be the simplest turn out to be very complicated when you think about it carefully.
6: Adjustment of the main output part of the mixer: The main output part of the mixer refers to the group volume and the total volume. For example, we can group the band into group 1-2; group the microphone into group 3-4; control the bass through the volume of group 5-6, control the auxiliary speakers through the volume of group 7-8, etc. In short, there are many A grouped mixer is easier to control. In addition, the group can choose to output signals individually or switch the group signal to the master volume mixing control of the mixer. Others such as channel faders are very simple, but the volume fader must be flexibly controlled according to the conditions of each input channel. Although this part of the adjustment is simple, it is very important. The main thing is to observe the input and output levels of each signal. The signal must not have serious distortion.
At this point, some important functions and operating techniques of the mixer have been basically mentioned. One thing I want to declare is: my technical article is for the general public. It is read by audio workers; those articles with profound theories, high-tech, and confusing things are written by expert figures for experts or quasi-experts! I think after all, most of them are basic audio workers, and what they need more are easy-to-understand technical articles!
Issues that need to be paid attention to when using the mixer:
1: Issues that need to be paid attention to in the signal input part of the mixer: As mentioned above, the input signal is generally divided into low impedance and high impedance. resistance input, but how to define whether a certain signal is low resistance or high resistance requires flexibility. For example, according to standards, electronic keyboards, electric guitars, etc. are high-impedance signals and must be input to the mixer using a 6.35 plug. However, in some places, the connection line from the stage to the mixer is too long and the line resistance is large. Interference from lighting and other systems has caused the background noise of this signal line to be very loud. Even if no audio source signal is input, turning up the gain of the input channel of this line on the mixer will cause a lot of noise. Just like what is described above: this line is a river. There is too much sediment in this river now, which means that there is a lot of noise in this line that cannot be changed, and the volume of the musical instruments on the other side of the line has been turned up to the maximum. But you can’t add more water, that is, the river can only put you so deep water, so what should you do? If you use a high-impedance signal input, it means that the water in the river has not increased, the water quality cannot be changed, and of course the sound quality cannot be changed; if you use an XLR plug to input the signal from a low-impedance socket, a little shallow water in the river will pass through the low-impedance amplifier. Zoom in, so the water is deeper, the water quality is better, and the sound quality is also better. It doesn’t seem real, but you can give it a try. In many of the projects I'm doing now, the bands all use XLR interfaces for low-impedance input. Although it seems irregular on the surface, it's actually a good way to reduce band noise. Therefore, sound workers need to be flexible, seek truth from facts, and find the best working methods in practice.
2: Issues that need attention in the AUX part: We know that AUX has pre-fader/post-fader conversion. The standard requires that the monitoring signal for the stage must be sent before the fader, but in performances, faders are generally used. It will be better to send later.
Take the AUX signal used for stage monitoring as an example: We use two CD players B to play music in turn. When the music on channel A has finished playing, we pull down the volume of the fader to turn off the sound, and then increase the volume of channel B. Push the fader up. But at this time, CD player A has not had time to eject the disc and is still playing. If the AUX signal sent after the fader is used at this time, the sound of CD player A will not come out from the stage speakers, but if it is used If the AUX signal is sent before the fader, the stage speakers will still send the sound of the CD player A. Then the stage speakers will have the sounds of two CD players A and B at the same time, and the singer will not be able to listen to it. Although at this time The main volume outside is not affected. Therefore, even the AUX auxiliary send part must be carefully adjusted.
3: Group allocation issues: The issues that need to be paid attention to in grouping are relatively simple, because the volumes of all groups can be output independently without switching to the main volume, so we need to be more careful in grouping, for example: we use Group 5-6 to control the volume of the bass, then group 5-6 of most input channels on the mixer can be pressed, but if it is a microphone channel, be careful, otherwise pressing group 5-6 of the microphone channel will Produce bass feedback; another point is that since we have independently output the signal from the corresponding output port at the back of the 5-6 group, there is no need to output it through the total volume of the mixer, that is, the 5-6 group to the mixer The switch for the overall volume of the sound console can no longer be pressed.
4: Phantom power: Most mixers will have a 48-volt phantom power supply, which can be used to drive a variety of condenser microphones, but since it is a current transmitted from the microphone line, Always check the microphone cable to ensure that it is smooth, otherwise a loud current surge sound will occur if the line contact is not good. Another phenomenon is: if you use a battery-powered conference condenser microphone in a mixer, do not turn on the phantom power, otherwise the two will interfere with each other and make a "rustling" sound like rain. . Audio
5: Recording input: The recording input channels of most mixers are simply controlled and then output directly through the mixer's master volume, so you must operate carefully to avoid misoperation and sudden loss of recording. The channel's sound is emitted from the mixer's master volume.
6: Output level: We know that the standard level for recording is 0dB, but in actual performances it usually exceeds a lot, even reaching +10 dB, so don’t be shocked when you see the red light. It’s disappointing. In fact, in actual use, it is reasonable for the signal level to slightly exceed the standard, and the sound effect produced at that time is also the best. Another thing to note is that when the peak level indicator reaches +4dB, the volume level of the output port corresponding to it reaches 0.775 volts at 0dB.
7: Some other function buttons: In addition to the important adjustment knobs, there are many function knobs, buttons or switches on the mixer, such as: forward and reverse phase conversion buttons, high cut or low cut buttons, We need to be proficient in the front and rear fader switching buttons, mute buttons, monitor buttons, etc. We need to be proficient in some of the frequently used ones. After understanding their basic functions, we should not adjust them frequently to avoid misoperations.
8: Headphones and live effects: Many sound engineers always like to wear headphones all the time to adjust the sound. Of course, headphones are very important, but after all, the sound in the headphones is very different from the sound on the scene, so it is still necessary Go to the venue and listen more. Don’t be unrealistic and wishful thinking and use headphones as a standard. You must know that when recording, headphones can be used as a standard; when performing live, headphones are just a tool, and the standard is our ears, which must be listened to live. 5
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