At present, there are auditory stimulators, excitation processing software, and excitation circuits in terms of audio signal processing in an excitation mode. One professional auditory exciter is more suitable for EFP.
The harmonic signal excited by the auditory exciter is designed through simulation and can be compared with the acoustic characteristics of the artificial reverberation simulation hall. Therefore, the generation of artificial harmonics should not be regarded simply as "falsehood" of the original signal and equal to distortion. The purpose of the exciter is to restore the harmonic components lost in the audio signal, effectively expand the high-frequency bandwidth and improve the signal-to-noise ratio, thereby improving the clarity and expressiveness of the sound reproduction. Moreover, the level of these harmonics is very low and has little effect on the power of the signal. Since the exciter has the above advantages, it can improve the sound quality by using it to process the signal.
In practice we use the AphexAuralExciter-III-250 (Ax-III-250) professional auditory exciter. The Ax-III-250 is a dual-channel processor. Each channel includes the same two audio paths, the Main Path and the Sidechain Path. The main path sends the audio signal from the input stage directly to the output stage, basically without any processing; the side chain path contains all the "heart" circuits of the exciter. Two audio signals are mixed at the additive circuit level and the mixing ratio is controlled by the Mix function. The Ax-III-250 has strong audio processing capabilities and can effectively eliminate noise and distortion.
2. Regulatory parametersThe exciter's main control parameters are threshold, tuning point, harmonics, fret and mixing ratio, etc. They are linked to generate high-frequency harmonics to be restored. The main controls of the Ax-III-250 are:
(1) Noise reduction threshold (NRThreshold). The control provides a threshold setting range of -60~+30dB, the purpose is to keep the noise level out of the excitation processing circuit and perform noise reduction.
(2) Tuning point (Tune). This control sets the rising edge frequency of the second-order high-pass filter in the side-chain path and establishes the operating frequency band for excitation. The frequency control range is 700 Hz to 7 kHz.
(3) Peaking. This control provides a buffering effect for the tuning point. When the control amount changes from the minimum to the maximum, the pre-emphasis at the tuning point frequency increases gradually. At the same time, before the tuning point is pre-emphasized, there will be a small notch, which will deepen as the peaking control increases.
(4) Null Fill (Null Fill). The role of zero-value compensation control is to adjust a band-pass signal that is added to the high-pass signal in the side-chain path to compensate for "phase loss."
There is a certain delay in the signal in the side chain path, which can cause transient waveform distortion, making the sound louder. At the same time, there will be a small notch near the tuning point on the output equalization curve. This notch will increase the frequency near the tuning point, making the higher frequency signal heavier. This effect is often needed. However, in order to compensate for phase loss, de-emphasis is performed using zero-value compensation control, thereby improving the expression and realism of the sound.
(5) Harmonic. Tuning control is used to adjust the amount of harmonics generated. Harmonics are generated by the VCA modulation process in the side chain path and do not affect the signal level in the side chain path. The harmonic components generated by the internal harmonic generator are based on a complex set of simulation operations, taking into account transient and steady sound quality and the corresponding original signal amplitude.
If the control volume is increased, the harmonic components will be increased by the odd-even harmonic ratio of the fret control. Moreover, the generated harmonics are not harmonic distortions, because they are intelligently generated and form a power envelope that results in improved sound quality rather than degradation.
(6) Timber (TImbre). The fret control is used to set the type and arrangement of harmonics, ie the ratio of odd and even harmonics. Even more harmonics sound softer, odd harmonics sound more blunt.
(7) Mix ratio. The role of mixing ratio control is to mix the enhanced signals into the original signal. The control range is from 0dB (that is, zero gain) to +14dB (indicating that the signal above the threshold is boosted by 14dB).
In addition, the Ax-III-250 also provides a single-choice side-by-side (Solo) function.
3, system accessThe exciter's access generally takes two forms: In-Line and Sidechain. as shown in picture 2. In most cases, the exciter is connected between two devices using a serial connection method. When using the side chain connection method, use the Solo function to disconnect the audio signal from the main path, and let only the pure excitation signal enter the mixing console. Mix the original signal and the pure excitation effect signal on the mixing console. This is very important. This connection method is equivalent to moving the Mixer control of the exciter to the mixer, and the mixer itself is a mixing console, so it is more convenient and flexible to control, which is advantageous for accurately tracking and controlling the auditory effects.
In practice, an Ax-III-250 dual channel is used to process multiple audio signals in an EFP at the same time. The exciter is connected to the audio system as shown in FIG. CH1 channels are assigned to vocals and CH2 channels are assigned to music. At this time, the auditory stimulator is in the form of a side link, the original flow of the program signal is not changed, the signal is transmitted and mixed according to the original channel, and two pure excitation effects are provided, and these harmonics are input to the source of the exciter. Signals are closely related to music and dynamics. The original signal and the pure excitation signal are only mixed on the mixing console.
The specific approach is: using a set of control parameters of CH1 to process FM audio or vocals from wireless microphones, and using another set of control parameters of CH2 to deal with music or other sounds (such as electroacoustic bands, etc.) whose sound quality is to be improved. Since the sound quality of these program sources is inconsistent, it is necessary to determine the amount of incentives to be added according to the condition of the material and to follow the adjustment and mixture ratio.
Actuator schematic circuit diagramThe schematic circuit diagram of audio exciter. Among them, the audio signal is input to the inverting buffer iqA via cr and RI, and its 7-pin output signal is divided into two paths. All the way directly through the input synthesis output stage composed by iqD. Another way is to input the voltage-controlled variable-state high-pass filter composed of iqB, IC3A, and IC3B via R7. The corner frequency is determined by the internal voltage-controlled variable transconductance elements Rl5, Rzs, q, cll, and Ic and passed through the potentiometer. The adjustment of RPi causes the corner frequency to change from 2 to 8 kHz, and below the corner frequency, the signal attenuates by 12 dB octave. Adjusting RPZA can change the negative feedback amount of the IC3A9 pin band-pass output to the ICLB9 pin inverting input, thus changing the Q value of the filter, because Q = (尉‰ + Rg)/R ll, the adjustment range of the mouth value is l- 0~1, 50IC3 is a dual operational transconductance amplifier model 13600. The ICIB8 pin is the output of the voltage controlled state variable high pass filter. The actual circuit is shown in the figure below.
(1) Determination of motivating objects: We need to use exciter to deal with what kind of audio source should have a clear concept, whether to deal with music alone or to deal with vocals alone? Or both? In general, the effect of the exciter on vocal sound is more pronounced; the effect on individual music processing is also obvious; but the effect of dealing with a mixture of music and vocals is relatively insignificant.
(2) The connection of the exciter: The connection of the exciter is basically connected in the signal path that needs to be stimulated in the sound system like peripheral equipment such as an equalizer. When stimulating different targets, the connection method of the exciter is also different. For example, in a mixing console, 1-2 groups are vocals. If vocals are to be stimulated, the exciter needs to be inserted. The plug/out connector is connected to the 1-2 channel of the mixing console; if the 3-4 group's band is also to be stimulated, an additional exciter must be added to the mixing console using the plug-in/out connector. 3-4 grouping; if you want to carry out comprehensive processing, then in the mixer main channel in series with an exciter on it. Of course, the exciter can also send out the signal from the AUX like an effector, and then return to the console, which can adjust which channels need to be stimulated, how much force needs to be handled, and so on, which is actually more flexible. In short, the specific connection of the exciter must be flexibly used according to the situation!
(III) Adjustment method of exciter:
Audio stimulators are not used in audio systems at present. The main reason is that engineers do not pay enough attention to stimulators. In addition, there are not many high-quality stimulators in the industry in recent years, so now they feel that stimulators are a bit "marginal." melted. The most famous actuators in the industry are: Aphex, BBE, BEHRINGER, etc. They have their own characteristics, but the general functions, principles and parameters are basically the same. Here I don't specifically introduce an exciter, just simply talk about Overall aspects:
The exciter function keys introduce:1. IN/OUT plus and no exciter effect selection: This key is mainly used for effect comparison when adjusting.
2, TUNE (tuning) exciter signal fundamental frequency adjustment: mainly used to select the frequency of excitation processing.
3, MIX (mixed) harmonic output control: mainly used to control the size of the incentive intensity.
4. HIGH/NORMAL: HIGH is suitable for stimulating single sound sources such as vocals and musical instruments; NORMAL is suitable for stimulating broad musical compositions such as whole music.
The above four function keys are called: auditory exciter parts and are mainly used to adjust the penetrating power of high-frequency harmonics and sound.
5, OVERHANG (bass hold time): This is mainly for bass length adjustment.
6, GIRTH (low volume): Bass strength adjustment.
The above two function keys are unique to the exciter with a low-frequency extension function and can adjust bass sounds.
Actuator adjustment method:1. IN/OUT is placed in “INâ€: The corresponding indicator lights up at this time, so that the exciter will enter the working state.
2. TUNE is placed at 12 o'clock position: This knob should be flexibly adjusted according to the need of the excitation frequency.
3. Place HIGH/NORMAL in the desired position: NORMAL in the general processing and HIGH in other processing.
4, MIX (Harmonic Amount) and GIRTH (Low Volume): all placed in the smallest position when starting adjustment.
5. Raise the MIX until you hear a squeaky sound (brightening): Be careful to listen. This sound is not particularly noticeable.
6, tune TUNE, to improve the tone or penetration of the sound: to pay attention to identify the tone, adjust the music and the microphone can be adjusted in turn, generally adjusted to a clock-like 11-14 o'clock position.
7. Repeatedly adjust the MIX until the harmonic effect is satisfactory: generally adjust to the 13-15 o'clock position similar to the clock.
1. When connecting the exciter in the sound system, we must pay attention to the flow of the signal. If we are preparing to use an exciter for a comprehensive treatment of music and vocals in a mixing console, then we can use the master of the mixing console. An exciter is connected in series after the channel output signal; if only the 3-4 groups in the mixer are processed, then 3-4 groups are used: the plug-in/out interface connects an exciter, so that 3- After the group 4 is energized, it is sent out through the main channel signal of the mixing console; of course, if the 3-4 grouping sound is not transmitted through the main channel of the mixing console at this time, the 3-4 grouping itself will be passed directly. The signal output port is directly sent out, so we can not use the plug-in/out method to connect the exciter, and can directly connect an exciter after the 3-4 group output signal. Seemingly simple, if the connection is wrong, then the whole effect has changed. Of course, we must fully understand how to connect and use the exciter.
2. If there is a level selection on the rear panel of the exciter, it is usually +4 and -10dB or +4 and -20dB, then we must choose it in the +4dB position so as to ensure the matching of the signal level.
3. When using IN/OUT vs. non-enhanced sound effects, many sound engineers have no way of recognizing the subtle differences in the sound, because the sound from the speakers rarely radiates directly into the ears of the sound engineer. It is difficult to accurately distinguish between added and unstimulated sound effects. In fact, there is a simple way: if we put the output signal of the left channel of the exciter into the channel 1 of the mixer, but notice that the volume fader of this channel should be turned off. Then we can put on headphones to listen to the sound of Channel 1 alone. At this time, we have a very good ability to distinguish between added and unexcited sound effects. Then we remove the headphone and adjust the right channel of the exciter. Then identify the effect from the live speakers, so that the two will be able to call up a perfect effect soon.
4, in the music-based sound system, such as: disco dance hall, the use of stimulator can be a substantial adjustment, bass volume and bass time can be adjusted to the satisfaction, the middle and high can also be significant Adjust to achieve a strong penetration. Because of the turbulence in these places, the sound absorption is very bad, and the noise floor is large, so it is very necessary to use the exciter to adjust.
5, in the vocal-based sound system, such as: song table, use the exciter adjustment to be cautious, bass volume and bass time must be repeatedly adjusted, bass too much affect the clarity of the voice, bass Too little sound is too thin and not full, so adjust it to the right place. The adjustment of the middle and high notes must be adjusted flexibly according to different vocals. Because the pitch frequency of the male singer and the female singer are different, the harmonics (overtones) that need to be handled by the exciter will certainly be different. Therefore, pay attention to the difference in this aspect when adjusting.
6, some of the sound field smooth reflection area is too much, so the high-frequency reflection is very powerful, the sound quality is also very noisy, at this time if you add the exciter to increase the "penetration" is undoubtedly worse, the high-frequency will become more harsh, noisy Therefore, a good sound field is very important, and no place can use an exciter.
8, to enhance OVERTHANG, tune to its indicator light: generally adjusted to a clock-like 11-14 o'clock position, the bass time is too short not fullness, too long and easy to muddy, to be careful adjustment.
9. Raise GIRTH and adjust OVERTHANG at the same time until the bass effect is satisfied: Generally adjust to a clock-like 10-13 o'clock position.
During the adjustment process, IN/OUT can be used to compare the sound effects with and without excitation, and repeated adjustments are made until the treble is bright and clear. The bass sound is flexible and the soft and hard strength is appropriate. Of course, there are various types of actuators, and their functions and adjustment methods are different. We can only adjust each audio equipment only by learning more, watching more, and listening more.
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