The voice commander in the sound system

Stage performance, conference room sound reinforcement, KTV, recording production, as long as there are multiple sound sources at the same time, it is inseparable from the mixer. Many people first see a mixer full of knobs and faders, only to find it complicated and difficult to understand; Stripping away the complicated panels, it is essentially a set of audio signal dispatching center, which is responsible for collecting, modifying and deploying all kinds of sounds, so that people's voices, musical instruments and background music are distinct and harmonious.

First, the four core missions of the mixer

1. Signal amplification and level matching
The sound waves picked up by the microphone are very weak and cannot be transmitted directly. The mixer has a built-in voice amplifier, which amplifies the weak microphone signal in the first stage through Gain gain; The line signal level output by mobile phone players and musical instruments is higher, and the line input mode can be switched. Adjusting the gain reasonably is the first hurdle to get clean sound and avoid noise and sonic boom.

2. Tone carving and balanced decoration (EQ)
Equalizer is like a sound palette, which divides low frequency, intermediate frequency and high frequency bands: low frequency determines the thickness of sound, and human voice is thin and empty without low frequency; Intermediate frequency affects clarity and is the most critical frequency band for language and lead vocals. High frequency gives a sense of transparency, and the sound is clear after upgrading, and it is harsh when it is excessive. With the low-cut HPF function, it can filter out the redundant low frequency below 80–100 Hz, eliminate the buzzing noise caused by ground vibration and air conditioning, and is also a common means to prevent howling.

3. Volume balance, multi-channel mixing
Multi-channel sounds are collected in the mixer, and the volume of each channel fader is adjusted. The lead singer can't be covered by accompaniment, and the background music needs to be moderately highlighted when the instrument is solo; Audio-visual PAN knob can also locate the position of sound in the left and right channels of stereo, creating a sense of space and avoiding all sounds being crowded in the center.

4. Signal distribution and effect scheduling
With the aid of auxiliary channels for sending AUX and FX effects, human voices can be sent to reverberation and delay effectors, adding a sense of space atmosphere; At the same time, the stage echo signal is output independently, so that the singers on the stage can hear their own voices. The mixer realizes the separate regulation of "the main amplification sound heard by the audience" and "the stage monitoring sound", and does not interfere with each other.

Two main types: analog mixer VS digital mixer.
Analog mixer
The whole machine relies on the physical circuit to process audio, one knob corresponds to one function, all parameters are clear at a glance, and the threshold for getting started is low. It is ready to use, without complicated menu operation, suitable for small activities, conference rooms, small bands and beginners. Shortboard is obvious: parameters cannot be saved, and it needs to be debugged again every time it is used; Function expansion is limited, and too many cables are easy to introduce electromagnetic interference. Yamaha MG series and Belinda portable mixer are the mainstream models in the market.

touchmix mixers
Convert audio into digital signal operation processing, and integrate a lot of functions such as compression, feedback suppression, multi-stage equalization, effector and so on. The biggest advantage is scene storage, which can be saved with one click after debugging, and can be retrieved quickly in the next activity; Support flat wireless remote tuning, and the channel expansion ability is stronger. Widely used in large-scale performances, theaters and professional recording. Disadvantages: the operation depends on the on-screen menu, the novice learning cycle is longer, and the price of the same number of channels is higher than that of the analog mixer.

Third, the tuning misunderstanding that novices are most likely to step on
1. Confuse gain with channel fader

The gain is responsible for the original signal level, and the fader only attenuates the volume. Correct sequence: adjust the gain first, and the peak light flashes occasionally with yellow light, and the red light is rarely triggered. Don't turn the gain down to a minimum, relying on the fader to push up the volume will amplify the circuit noise.

2, the balance is greatly twisted.

EQ adjustment follows the principle of "small fine-tuning", giving priority to attenuating harsh frequency bands, and not frantically raising frequency bands; Blindly pulling up the high frequency can easily trigger howling.

3. The idle channel is not silent.

The unused microphone channel is kept open, and the ambient noise is continuously picked up, and the signal-to-noise ratio of the whole system decreases. Press the MUTE button in time when the channel is not used.

4, the effect is excessive

Reverberation is to create an atmosphere, and can't hide the original sound. The amount of human voice effect is moderate, too much will lead to weak and fuzzy voice, and the recognition will be greatly reduced.

5, switch the machine in reverse order

Boot sequence: sound source → mixer → power amplifier; Turn off the machine and reverse the operation. It is forbidden to hot plug the microphone cable when it is powered on, because the impact signal may damage the equipment.

Fourth, the scene simple selection reference
1. Small conference room, family K songs and small roadshows (4-6 microphones): 8-12 analog mixers, with the highest cost performance;
2. Small and medium-sized banquet halls, band performances, and occasional multi-event activities: 12-16 analog platforms with built-in effects;
3. Theatre, large-scale party and multiple fixed performances: digital mixer, which saves a lot of tuning time by relying on scene storage.

The mixer is never a simple "volume regulator". Excellent tuning is not only to eliminate noise and prevent howling, but also to balance the artistic level. Only by reading the signal flow direction and understanding the sound changes behind each set of knobs can we control this sound command center, so that each sound source can find a suitable position and present a harmonious and full listening experience.