The four important components of the sound reinforcement system peripheral equipment are: frequency divider, exciter, equalizer, and compressor. Of course, these previously emerging hardware devices are now concentrated in a digital audio processor. Here are just a split and talk about their respective features.
The task of the frequency divider is to divide the audio signals of different frequency bands, and the divided signals are output to the subsequent stages for amplification, and finally sent to the speakers of the corresponding frequency bands (high, medium and low units) for playback. High quality audio playback usually requires crossover processing.
There are two types of dividers:
1, power divider 2, electronic crossover
Power divider:
Behind the power amplifier, set inside the speaker, through the LC filter network (ie LC filter principle), the power audio signal output by the power amplifier is divided into bass, midrange and treble, respectively, to the speakers of the respective frequency bands. The connection is simple and convenient to use, but power consumption, audio valleys will occur, cross distortion will occur, its parameters are directly related to the speaker impedance, and the impedance of the speaker is a function of frequency, which deviates greatly from the nominal value, so the error Also larger, not conducive to adjustment.
Electronic crossover:
Located in front of the power amplifier, that is, the device that divides the audio signal before power amplification, and then divides the frequency and then amplifies them with separate power amplifiers to drive the corresponding speaker unit. Since the signal current is small, it can be realized by a smaller power electronic active filter, which is easier to adjust, reduces power loss, reduces interference between speaker units, and has small signal loss. However, since each channel uses an independent power amplifier (for the amplification characteristics of the frequency band), the cost is high and the circuit structure is complicated.
The exciter is a harmonic generator that uses human psychoacoustic characteristics to modify and beautify the sound signal. By adding various methods such as adding high-frequency harmonic components to the sound, it is possible to improve the sound quality, the timbre, and the penetration of the sound, and to increase the spatial sense of the sound.
Many exciter products not only create high-frequency harmonics, but also have functions such as low-frequency extension and music-style preset parameters, which make the bass effect more perfect and the music more expressive.
Using the exciter during mixing can also improve the clarity, intelligibility and expressiveness of the sound, making the sound more pleasant, reducing the listening fatigue and increasing the loudness. Although the exciter only adds about 0.5dB of harmonic content to the sound, actually it sounds like the volume is increased by about 10dB, which makes the auditory loudness of the sound increase significantly.
Not only that, but the use of the exciter can also make the sound positioning clear and hierarchical. Since the audio signal loses high-frequency harmonic components during transmission and recording, high-frequency noise occurs, and the excitation device can effectively compensate the signal. The adjustment of the exciter requires artificially discriminating the sound quality and tone of the system, and then adjusting according to the subjective hearing evaluation.
An equalizer is an electronic device that can independently adjust the amplification or attenuation of various frequency components of an audio signal. It compensates for the defects of the speaker and sound field by adjusting various frequency components of the audio signal, and modifies the sound source and other special purposes.
Equalizers fall into three categories:
1, graphic equalizer 2, parametric equalizer 3, room equalizer
Graphic equalizer:
Also known as chart equalizer, through the distribution of push-pull keys on the panel, the balanced compensation curve can be visually reflected. The improvement and attenuation of each frequency can be seen at a glance. It uses constant Q-value technology and has a push-pull for each frequency. The potentiometer, regardless of raising or attenuating a certain frequency, the frequency bandwidth (Q value) of the filter is always the same.
The commonly used professional graphic equalizer is to adjust the signal of 20Hz-20kHz into 10 segments, 15 segments, 27 segments and 31 segments. In this way, people can select different frequency equalizers according to different requirements.
The frequency points of the 10-band equalizer are distributed at octave intervals; the 15-band equalizer is a 2/3 octave equalizer, which is usually used when the requirements are not very high; the 31-band equalizer is 1/3 octave The equalizer is used in applications where fine adjustment and compensation are required. The graphic equalizer has a simple structure, is straightforward, and is widely used.
Parametric EQ:
Also known as parametric equalizer, the equalizer can be finely adjusted for various parameters of equalization adjustment. The parameters of the adjustment include frequency band, frequency point, gain and Q value, etc., can beautify, modify the sound, make the sound (or music) style More striking and colorful, to achieve the desired artistic effect.
Room equalizer:
The equalizer used to adjust the frequency response characteristic curve in the room, due to the difference in the amount of absorption (or reflection) of the decorative material to different frequencies and the influence of the normal resonance (standing wave), it is necessary to use the room equalizer pair. The frequency defects in Jiansheng are objectively compensated and adjusted. The finer the frequency band is, the sharper the adjusted peak is, that is, the higher the Q value, the finer the compensation during adjustment. The thicker the frequency band is, the wider the adjustment peak is. When the sound field transmission frequency characteristic curve is more complicated, it is more difficult to compensate. .
The compressor is a general term for compressors and limiters. It can compress or limit the dynamics of audio electrical signals to a certain range.
Design principle
The design principle of the compressor is a variable gain amplifier, and its amplification factor (gain) can be automatically changed according to the strength of the input signal, which is inversely proportional. When the input signal is higher than the set threshold (threshold), the higher part will be compressed according to the set ratio. When the compression ratio exceeds 10:1, the compressor becomes the limiter, so the limiter actually The top is a special case of the compressor. The limiter's compression ratio is 10:1-20:1, which is equivalent to setting an insurmountable upper limit value for the signal.
The pressure limiter can make the audio signal change smoothly and unobtrusive, play the role of large pressure and small, effectively prevent over-excitation distortion, and limit the peak value of the large-level signal to protect the equipment of the latter stage from damage. By setting its noise gate parameters, the noise level can be well reduced and the signal-to-noise ratio of the signal transmission channel can be improved. In the landscaping of the modified sound, the sound source (vocal, musical instrument, etc.) can be made strong and the details are clear and identifiable.
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