It is well known that the main functions of equalizers are to adjust the timbre, adjust the sound field and suppress the sound feedback. There are many articles on how to adjust the timbre. What I want to introduce here is how to use professional multi-paragraph pattern room equalizer to adjust the sound field and adjust the sound feedback.  

Nowadays, the graphic equalizer used in professional audio systems is usually about 31, and the Q value of the push-pull potentiometer is constant, which is generally 1/3 octave. Therefore, the bandwidth of the filter is always unchanged whether the frequency is promoted or attenuated, and the degree of frequency promotion and attenuation is generally 6-18dB, and the most commonly used one is 12dB. The pattern equalizer can reflect the increase and decrease of each frequency intuitively through the distribution of push and pull keys on the panel. Commonly used professional graphic equalizer frequency adjustment range is generally 20Hz~20kHz, frequency adjustment points are generally divided from low to high: There are 31 frequency points in total at 20Hz, 25Hz, 32Hz, 40Hz, 50Hz, 63Hz, 80Hz, 100Hz, 125Hz, 160Hz, 200Hz, 315Hz, 400Hz, 500Hz, 630Hz, 800Hz, 1kHz, 1.25khz, 1.6khz, 2kHz, 2.5khz, 3.15khz, 4kHz, 5kHz, 6.3khz, 8kHz, 10kHz, 12.6khz, 16kHz and 20kHz. Because it has a main function is used to adjust the indoor sound field, so it is also called: professional multi - paragraph schema room equalizer.  

I will write down my experience of using equalizer over the years for your reference

1. Adjust the sound field with an equalizer:

Among the three major functions of professional equalizers, adjusting timbre should be the most basic and frequently used function. Even at present, many sound engineers only know that equalizers can adjust timbre, but they do not know that the more important functions of professional schema room equalizers are to adjust sound field and suppress sound feedback. Using room equalizer to adjust the sound field, the very professional method is to use the pink noise generator and real-time spectrometer to adjust. But we now most of the sound engineer is impossible to have the equipment, can use local materials, the use of the existing equipment to adjust sound field, the easiest and most practical way is to use microphone to adjust, but how to use the microphone to adjust and adapt acoustic feedback there are some articles about, but I think an introduction not detailed enough or is not easy to understand, in the years of work, I summarized a set of simple, practical and easy to understand adjustment method, specific steps are as follows:

A. First, find A microphone with A relatively straight frequency response curve and A wide frequency response range, preferably A condenser microphone, or A moving-coil wired or wireless microphone of good quality. The microphone is fixed on the microphone shelf and placed in an optimal listening area of the sound field, with a height of about 1.2 meters. The horizontal position of the microphone picking up head is flat with the central axis of the main speaker, basically forming an isosceles triangle with the main speaker.

B, in addition to the room to be adjusted when equalizer bypass through other peripheral equipment, regulate point reset all equalizer, tuning stage channel equalizer receiver is also want to direct do adjustment, power amplifier open the volume and open to the right position, then open the total volume of the mixer, began to slowly push the microphone volume up pusher, hear the sound slightly back to lose, then put the microphone volume pusher about 6-9 dB down.

C. Then, the room equalizer is used to gradually improve from each point of 50Hz to 16kHz. Generally, the frequency below 50Hz and above 16kHz will not produce acoustic feedback. The specific adjustment steps are as follows:

1, find out back to lose the best frequency point: the greatest influence of sound field back to lose points have 2 or so commonly, if in a code-named: W ballroom, when we to 400 hz and 4 KHZ to greatly improve both the doping, and the other frequency point even made substantial ascension (generally ascend around 12 dB) did not produce sound back to lose, so we are sure to lose in this sound field most have two points, and is: 400 hz and 4 KHZ, at this time we want to look around 6 dB attenuation of the two points, it can facilitate the next step of operation. Of course, the frequency of different sound fields is not the same.

2, find out the feedback the better frequency point: this point usually has three or so, at this time we put tuning stage microphone volume is big, again on the equalizer in addition to 400 hz and 4 KHZ frequency points one by one, to dramatically improve, if discovered 200 hz, 1 KHZ, 5 KHZ produced back to lose, the adjustment of the second step is done.

3. Process the return input frequency: through the above adjustment, we have found 5 return input points. We can attenuate the most severe points of return input, 400Hz and 4kHz, by about 6-9 dB. The sound field is basically well adjusted at this time by feeding back the strong frequency points of 200Hz, 1KHz and 5KHz into the attenuation of 3-6 dB.

2. Adjust the acoustic feedback with equalizer:

Many sound engineers have a puzzle: isn't adjusting the sound field the same thing as adjusting the sound feedback? Why separate the two? In fact, there is of course a difference between the two, although the adjustment steps and methods are the same, but its goal and effect is not the same. Tuning the sound field is only to find the shortcomings of this sound field and optimize, but there is no way to solve most of the microphone voice feedback, I say here is also colloquially called: feedback. Or in the code-named: W ballroom, for example, the dance hall sound system using six microphone, only then the ballroom and three stage for actors, imagine if this 6 microphone is not the same brand again, and their parameters and each are not identical, to think in this case to completely avoid to lose how difficult it will be. But no matter how difficult it is, we need to find a way to solve it. We can minimize and avoid acoustic feedback through the following methods:

First, we sorted out all the microphones and selected the ones we used most often. Let's say we chose 2 AKG microphones and 2 SHURE microphones, then we adjusted the sound feedback in the same way as we adjusted the sound field:

1. For example, we can first take a SHURE microphone, fix it on the microphone stand, and look for return input points in three stage ranges respectively. Suppose we find a main return point of 500Hz in the area of Stage A; A 630Hz main return point is found in the b stage area. A major 800Hz return point was also found in the c stage region.

2. Then, take an AKG microphone and fix it on the microphone stand. Then, look for the return points within the scope of three stages. A main return point of 2.5KHz was found in b stage area. A 3.15khz main return point was also found in the c stage area. In this way, two kinds of microphones were used to find six return points in three stage areas: 500Hz, 630Hz, 800Hz, 1.25khz, 2.5KHz and 3.15khz. Then, these points were attenuated by 3-9 dB according to the return size on the equalizer. Of course, in the case of the same microphone volume within these three stage areas, stage A may have the most severe return loss and find 3 points, while stage B and Stage C do not even have one return point, so it should be adjusted flexibly according to the situation.

3. Use the main microphone to search the return points in the main performance area one by one, and then search the areas where the actors do not often go but are likely to go, to see if there are any return points; And then use the receiver often do not use in accordance with the above order to start the search again back to lose points, so the ballroom acoustic feedback will be very good control, will not, of course, excess attenuation equalizer, if the recognition of the equalizer attenuation, holes, in order to do even the continuity of sound and tones are not guaranteed.

3. Use equalizer to adjust the timbre:

Once the sound field and input point are adjusted, the most common function of the professional graphic room equalizer is to adjust the sound color. Of course, the frequency of input point should be taken into account when adjusting the sound color. If possible, an equalizer can be added to adjust the sound color. In fact, different sound equipment and different sound fields will adjust equalizers differently, so it is impossible to have a relatively standard and fixed adjustment method. However, in my more than ten years of work, I have summarized a set of adjustment methods that are relatively suitable for most places. You can have a try:

A. Low-frequency adjustment -- adjust the pitch and fullness and firmness of all sound sources:

I'm used to dividing the frequency range from 20Hz to 315Hz into low bands. The focus of this adjustment is to pay attention to the main pitch of the various sound sources. It's like a pyramid, without the base part, there will be no steeple part.

In terms of specific operations:

1, 20Hz, and 32Hz are basically completely attenuated, because the bass frequencies of many speakers have not yet descended to this frequency band.

2. The two frequencies of 40Hz and 50Hz are exactly the 220V ac current in China. In order to reduce the interference of the power supply, we generally attenuate these two frequencies by about 5 dB.

3. The three frequencies, 63Hz, 80Hz and 100Hz, determine the fullness of the sound source. Generally, it is not necessary to make a big improvement and attenuation.

4. The four points, 125Hz, 160Hz, 200Hz and 250Hz, determine the strength and firmness of the sound source. If the sound is too much improved, it will be stiff; if the sound is too much attenuated, it will be fuzzy and virtual.

5, the whole low frequency band needs to pay attention to one point is that if the bass part is increased by 3 dB, the load of the power amplifier will be doubled. Therefore, it is necessary to be careful when adjusting. It is necessary to pay attention to not only the timbre but also the sound field as well as the endurance of the power amplifier.

B. Adjustment of middle frequency band -- adjust the second and third overtones, roundness and brightness of various sound sources:

I'm used to dividing the frequency range from 400Hz to 2.5KHz into the middle band, and you know that the main pitch of most sound sources is going to be in the bass, so they have 2 overtones, 3 overtones, 4 overtones... It's going to be in the mid range; Of course, there are also some sound sources whose main pitch is in the middle band due to the higher frequency. In short, the focus of this section of adjustment is to tune most of the second and third overtones of the sound source and the roundness and brightness of the timbre.

In terms of specific operations:

1. The five frequencies, 315Hz, 400Hz, 500Hz, 630Hz and 800Hz, affect the strength and roundness of the sound source. The frequency of this segment is rarely increased, because it will affect the sound quality. When you raise the sound quality too much between 630Hz and 800Hz, it becomes like the sound on the phone.

2. The five frequency points of 1kHz, 1.25khz, 1.6khz, 2kHz and 2.5khz affect the brightness of sound source. These frequencies are the most sensitive in human ear hearing and therefore have the greatest impact on the overall timbre.

The whole middle frequency band is also the frequency range that the sound feedback is the easiest to generate, so the adjustment of the middle frequency band frequency point should be very flexible and careful.

C. Adjustment of high frequency band -- adjust multi-overtone and color sense and penetration of various sound sources: I am used to dividing the frequency range from 3.15KHz to 20kHz into high frequency band. The emphasis of this adjustment is to pay attention to the overtone part of various sound sources as well as color sense and penetration.

In terms of specific operations:

1.15KHz, 4kHz, 5kHz and 6.3khz are the main parts of the high pitch section. If these frequency points are excessively raised, the sound will easily produce burr sensation or high pitch feedback. Excessive attenuation of the sound will appear dull, non-magnetic and non-dynamic. So be careful and operate carefully.

2, 8kHz, 10kHz and 12.5khz affect the level and color of sound.

3, 16 KHZ, 20 KHZ due to the many speakers of high frequency also amounted to less than 20 KHZ, coupled with the human ear can hear less high frequency, so we usually make 20 KHZ this points to a big attenuation, and the 16 KHZ frequency point in fact is very important, if the attenuation, so that in the high radiant golden light feeling would not.

What should be paid attention to in the whole high frequency band is that when feedback is generated in this frequency band, although it will not be obvious in the human ear hearing, continuous feedback will cause serious damage to the high pitch. Therefore, we should not take it lightly and deal with it seriously.

At this point, it should be clear to you that it is difficult for equalizers to have a relatively fixed and silly adjustment mode. However, I still think there is a certain pattern to be found. Here I will say a general mode summarized by myself, and you can try it (in the following frequencies, + means improvement; for example, +3 means improvement of 3 dB; - represents attenuation, for example, -12 represents attenuation of 12 dB; 0 means no promotion or attenuation) :

A. Adjustment of equalizers in most comprehensive performance sound systems:

20Hz[-12], 25Hz[-12], 32Hz[-10], 40Hz[-8], 50Hz[-4], 63Hz[-2], 80Hz[0], 100Hz[0], 125Hz[0], 160Hz[-2], 200Hz[-3], 250Hz[-3], 315Hz[-3], 400Hz[0], 500Hz[0], 630Hz[-2], 800Hz[-1], 1kHz[0], 1.25kHz[0], 1.6khz [-2], 2kHz[-3] 2.5 kHz, 3.15 kHz [3], [2], 4 kHz [2], [2] 5 kHz, 6.3 kHz [3], [0] 8 kHz, 10 kHz, 12.5 kHz [+ 2], [+ 3), 16 kHz [0], [9] 20 kHz.

B. Adjustment of equalizers in most disco and slow bar sound systems:

20Hz[-12], 25Hz[-12], 32Hz[-8], 40Hz[-5], 50Hz[-2], 63Hz[0], 80Hz[0], 100Hz[0], 125Hz[+2], 160Hz[+2], 200Hz[+3], 250Hz[+1], 315Hz[-1], 400Hz[0], 500Hz[0], 630Hz[-2], 800Hz[-1], 1kHz[0], 1.25kHz[0], 1.6khz [-2], 2kHz[-4], 2 . [2] 5 kHz, 3.15 kHz, 4 kHz [+ 2], [2], [2] 5 kHz, 6.3 kHz 8 kHz [3], [2], [0] 10 kHz, 12.5 kHz [0], 16 kHz [3], [9] 20 kHz.

Problems to note when using professional equalizers

1. Generally, the acoustic feedback is concentrated in the range of 100Hz -- 10kHz, and the adjustment should be targeted.

2. When adjusting the sound field, other peripheral devices except the room equalizer shall be directly connected by bypass, and the equalizer in the channel where the microphone is located on the mixing table shall also be directly connected without adjustment.

3. When using equalizer to adjust the acoustic feedback, only the pressure limiter is directly connected, other peripheral devices such as exciter should be adjusted to the optimal performance state, and the equalizer in the channel where the microphone is on the mixing table should also be adjusted to the optimal performance state, which is obviously different from the method of adjusting the sound field.

4. No matter using equalizer to adjust sound field or acoustic feedback, if there is a pressure limiter in the system, it should be directly connected, otherwise the microphone will be subjected to the pressure limiter treatment when it is input back at the beginning; When the feedback signal is very large and the pressure limiter cannot be compressed, the feedback will break the limit of the pressure limiter and become very severe, which will easily damage the equipment.

5. After years of practice, when adjusting the sound field and adjusting the sound feedback, a little background music can be played at the same time to make the sound field active and more convenient for adjustment.

Having said all this, I would like to conclude by saying that in a live performance, if the sound field is not properly adjusted, then the overall timbre and balance cannot be guaranteed. If the acoustic feedback is not adjusted well and even one sound is lost, it will be a serious problem. My consistent principle is: as long as the whole performance has one sound feedback, it will be a failure! So I often describe pushing the mixer during our performance as like pushing a ticking time bomb. I don't know when it will explode, so I really need to be very careful and feel like I'm walking on eggshells! So the sound engineer pressure is very big, if the recording time is not good we can be taped or edited, but if produced in the live performance even if is the frequent feedback, like pour out the water, is can't come back, so a lot of high level of recording engineer don't want to do the scene of the sound engineer.

Before said sound division is a kind of art and technical work, I would like to add one more: challenging! I hope that every sound engineer dares to face the pressure, dare to challenge themselves, and jointly improve the tuning level of our country!