At present, there are an auditory exciter (AuralExciter), an excitation processing software, and an excitation circuit in terms of excitation mode for audio signal processing. Among them, professional auditory exciters are more suitable for EFP.
The harmonic signals excited by the auditory exciter are simulated and can be analogized to the acoustic characteristics of the artificial reverberation simulation hall. Therefore, the generation of such artificial harmonics should not be simply considered as "false" of the original signal and is equivalent to distortion. The exciter is designed to recover the harmonic components lost by the audio signal, effectively extend the high frequency bandwidth and improve the signal to noise ratio, thereby improving the clarity and expressiveness of the sound reproduction. Moreover, the levels of these harmonics are very low and have little effect on the power of the signal. Since the exciter has the above advantages, it can improve the sound quality by processing the signal.
In practice we use the AphexAuralExciter-III-250 (Ax-III-250 for short) professional auditory exciter. The Ax-III-250 is a dual-channel processor. Each channel includes the same two audio paths, the main signal path (MainPath) and the side chain stimulated signal path (SidechainPath). The main path sends the audio signal from the input stage directly to the output stage with essentially no processing; the side chain path contains all the "heart" circuits of the exciter. The two audio signals are mixed at the adder 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, control parametersThe main control parameters of the exciter are threshold, tuning point, harmonic quantity, tone and mixing ratio, etc., which jointly generate the high frequency harmonics to be recovered. The main controls of the Ax-III-250 are:
(1) Noise reduction threshold (NRThreshold). The control provides a threshold setting range of -60 to +30 dB in order to keep the noise level out of the excitation processing circuit and to reduce noise.
(2) Tuning point (Tune). The control sets the rising edge frequency point of the second-order high-pass filter in the side chain path, and establishes the working frequency band of the excitation, and the frequency control range is 700 Hz to 7 kHz.
(3) Peaking. This control provides a buffering effect for the tuning point. When the amount of control is from the minimum to the maximum, the pre-emphasis of the tuning point frequency is gradually increased. At the same time, a small notch will appear before the tuning point is pre-emphasized, which will deepen as the peaking control increases.
(4) Zero value compensation (NullFill). The function of the zero-value compensation control is to adjust a band-pass signal that is applied 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 causes distortion of the transient waveform and makes the sound louder. At the same time, small notches appear near the tuning point on the output equalization curve. This notch de-emphasizes the frequency near the tuning point, making the signal in the higher band heavier. This effect is often needed. However, in order to compensate for phase loss, de-emphasis is performed with zero-value compensation control, thereby improving the expressiveness and realism of the sound.
(5) Harmonic amount (Harmonic). Tuning control is used to adjust the amount of harmonics generated. Harmonics are generated by VCA modulation processing in the side chain path, which does 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-state sound quality and corresponding original signal amplitudes.
If the amount of control is increased, the harmonic components will be increased in proportion to the odd-even harmonics controlled by the sound. Moreover, the harmonics produced are not harmonic distortions because they are intelligently generated and form a power envelope that causes the resulting sound quality to improve rather than deteriorate.
(6) Sounds (TImbre). The sound control is used to set the type and arrangement of harmonics, ie the ratio of odd and even harmonics. The sounds with even harmonics sound softer, and the sounds with more odd harmonics sound harder.
(7) Mix ratio (Mix). The purpose of the mixing ratio control is to mix the excitation-enhanced signal into the original signal, with a control range from 0 dB (ie, zero gain) to +14 dB (a 14 dB boost on the signal above the threshold).
In addition, the Ax-III-250 also provides a single side-by-side path (Solo) function.
3, system accessExciter access is generally available in two forms: In-Line and Sidechain. as shown in picture 2. In most cases, the exciter is connected between the two devices by a series connection method. When using the side-chain connection, the Solo function is used to disconnect the audio signal of the main path, and only the pure excitation signal enters the mixing console, and the original signal and the pure excitation effect signal are mixed on the mixer. This is very important. This connection is equivalent to moving the exciter's Mix control to the mixer, and the mixer itself is a mixing console, so the control is more convenient and flexible, which is beneficial for accurately tracking and controlling the hearing effect.
In practice, an Ax-III-250 dual channel is used to simultaneously process multiple audio signals in the EFP. Connect the exciter to the audio system as shown in Figure 3. The CH1 channel is assigned to the vocal use and the CH2 channel is assigned to the music. At this time, the auditory exciter 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 supplied to the source of the exciter. Signals are closely related to music and dynamics. The original signal and the pure excitation signal are mixed and mixed only on the mixer.
The specific method is to process FM audio or vocals from wireless microphones with a set of control parameters of CH1, and to process music or other sounds (such as electroacoustic bands) whose sound quality needs to be improved by another set of control parameters of CH2. Since the sound quality of these program sources is inconsistent, it is necessary to determine the amount of excitation addition according to the condition of the material, and to adjust the mixing ratio.
Schematic circuit diagram of the exciterA schematic circuit diagram of an acoustic actuator. Among them, the audio signal is input to the inverting buffer iqA via cr and RI, and the 7-pin output signal is divided into two paths. One way through the direct input of the composite output stage consisting of iqD. The other is a voltage-controlled state variable high-pass filter composed of iqB and IC3A and IC3B through R7 input. The corner frequency is determined by Rl5, Rzs, q, cll and Ic internal voltage-controlled variable transconductance components, and passes through the potentiometer. The adjustment of RPi causes the corner frequency to change between 2 and 8 kHz, and the signal below the corner frequency is l2 dB octave attenuation. Adjusting RPZA can change the negative feedback amount of IC3A9 pin bandpass output to the inverting input terminal of IClB9, 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-operation transconductance amplifier, model 13600. ICIB8 pin is the output of the voltage-controlled state variable high-pass filter. The actual circuit is shown below.
(1) Determination of incentive objects: We need to use the exciter to deal with what sound source to have a clear concept, whether to deal with music alone or vocal alone? Or both? In general, the effect of the exciter on the vocals is more obvious; the effect of the individual music processing is also obvious; but the effect of the mixture of music and vocals is relatively less obvious.
(2) Connection of the exciter: The connection of the exciter is basically connected in a signal path that needs to be excited in the acoustic system like a peripheral device such as an equalizer. When the excitation process is applied to different targets, the connection method of the exciter is also different. For example, in a mixer, 1-2 groups are vocals. If the vocal is to be motivated, the exciter should be inserted. / The plug-in interface is connected to the 1-2 group channel of the mixer; if the 3-4 group band is also motivated, then an exciter is added to the console using the plug-in/plug-out interface. The 3-4 group; if it is to be integrated, it is ok to connect an exciter in the main channel of the mixer. Of course, the exciter can also send the signal from the AUX like an effect, and then return to the mixer, so that you can adjust which channels need to be stimulated, how much force you need to process, etc., which is actually more flexible. In short, the specific connection of the exciter should be used flexibly according to the situation!
(3) Adjustment method of the exciter:
The audio exciter is not used too much in the audio system at present, mainly because the engineering company does not pay enough attention to the exciter. In addition, there are not many high-quality exciters in the industry in recent years, so now the exciter is a bit "edge". melted. At present, the more famous actuators in the industry are: Aphex, BBE, BEHRINGER, etc., each of which has its own characteristics, but the general functions, principles and parameters are basically the same. Here I will not specifically introduce a certain exciter, just briefly talk about it. Overall:
Exciter function key introduction:1, IN / OUT plus and no exciter effect selection: This button is mainly used to adjust the effect when adjusting.
2, TUNE (tuning) exciter signal fundamental frequency adjustment: mainly used to select the frequency that requires excitation processing.
3, MIX (mixed) harmonic output control: mainly used to control the intensity of the excitation.
4. HIGH/NORMAL: Among them, HIGH is suitable for excitation processing for single sound sources such as vocals and musical instruments; NORMAL is suitable for stimulating music with wide range of music such as overall music.
The above four function keys are called: the auditory exciter part, which is mainly used to adjust the penetration force 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 low frequency extension function, which can adjust the bass sound.
Actuator adjustment method:1. IN/OUT is placed in “INâ€: At this time, the corresponding indicator lights up, so that the exciter will enter the working state.
2. TUNE is placed at 12 o'clock: this knob should be flexibly adjusted according to the needs of the excitation frequency.
3. HIGH/NORMAL is placed in the desired position: in the comprehensive processing, it is placed in NORMAL, and the other processing is placed in HIGH.
4. MIX (Harmonic Amount) and GIRTH (Low Volume): They are placed in the minimum position when starting the adjustment.
5. Raise the MIX until you hear the chrome sound (the sound is brighter): Listen carefully, this sound is not particularly noticeable.
6, adjust TUNE, to improve the sound of the sound or penetrating power: pay attention to distinguish the tone, adjustment can be adjusted with music and microphone in turn, generally adjusted to a similar clock 11-14 o'clock position.
7. Repeat the adjustment of 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, be sure to pay attention to the flow of the signal. If in a mixer, we are going to use an exciter to comprehensively process the music and vocals, then it can be in the main mixer. The channel output signal is followed by an exciter in series; if only the 3-4 groups in the mixer are processed, then the 3-4 grouping is used: the plug-in/plug-out interface is connected to an exciter, such that 3- After the 4 groups are stimulated, they are sent out through the main channel signal of the mixer; of course, if the sound of the 3-4 group is not sent through the main channel of the mixer at this time, it is directly separated by 3-4. The signal output port is sent directly, then we can not use: insert/plug method to connect the exciter, and can directly connect one exciter after the output signal of 3-4 groups. It seems simple, if the connection is wrong, the whole effect has also changed. Of course, we must fully understand the connection and use of the exciter, and we must rely on ourselves to study more.
2. If the rear panel of the exciter has a level selection, it is generally +4 and -10dB or +4 and -20dB. Then we must select it at the +4dB position to ensure the signal level is matched.
3. When using IN/OUT contrast plus unincentive sound effects, many sound engineers can't distinguish the slight difference in sound, because the sound released in the speaker can rarely radiate directly into the sound engineer's ear. It is difficult to accurately identify the sound effects of adding and not stimulating. In fact, there is a simple way: if we connect the output signal of the left channel of the exciter to the first channel of the mixer, but pay attention to the volume fader of this channel to be turned off. Then we can wear the headphones to monitor the sound of the first channel separately. At this time, we have a high discrimination ability for the sound effect with and without excitation, and then remove the right channel of the earphone adjustment actuator. Then identify the effect from the live speakers, so that the two can quickly bring out a perfect effect.
4, in the music-based audio system, such as: in the disco ballroom, the use of the exciter can make a large adjustment, the bass volume and bass time can be adjusted to satisfaction, the middle and high notes can also be large Adjust to achieve strong penetration. Because of the crowds in these places, the sound absorption is very strong, and the noise floor is large, it is very necessary to use the exciter to adjust.
5. In the vocal-based audio system, for example, in the song-song stage, be careful when using the exciter adjustment. The bass volume and bass time should be adjusted repeatedly. The bass too much affects the clarity of the human voice. Too little sound seems too thin and not full, so adjust it to the right. The adjustment of the middle and high sounds is actually adjusted according to different vocals. Because the male and female singers have different pitch frequencies, the harmonics (overtones) that need to be processed by the exciter will of course be different. Therefore, pay attention to the difference in this aspect when adjusting.
6. Some sound fields have too many reflective areas, so the reflection of the treble is very powerful, and the sound quality is very noisy. At this time, if you add the exciter to increase the "penetration force", it will undoubtedly worsen the treble, and the treble will become more harsh and noisy. Therefore, a good sound field is very important, and no exciter can be used in any place.
8, enhance OVERTHANG, adjust its indicator light: generally adjust to a similar clock 11-14 o'clock position, bass time is too short, no fullness, too long and easy to turbid, be careful to adjust.
9. Increase GIRTH and adjust OVERTHANG until the bass effect is satisfactory: generally adjust to a 10-13 o'clock position similar to the clock.
During the adjustment process, IN/OUT can be used to compare the sound effects with and without excitation. Repeat the adjustment until the treble is bright and clear. The bass is full and flexible, and the soft and hard strength is suitable. Of course, there are various types of exciters, and their functions and adjustment methods are different. We only need to learn more, see more, and listen more to adjust each audio device.
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