Equalizer (EQ) is an electronic device that can separately adjust the amount of amplification applied to the electrical signals of various frequency components. By adjusting electrical signals at different frequencies it compensates for the shortcomings of the speakers and of the sound field, compensates for and refines various sound sources, and serves other special purposes. On most mixing consoles the equalizer can adjust three frequency bands separately: high, middle and low. In communication systems, inserting an equalizer into a baseband system can reduce the effect of inter-symbol interference.
Here we will focus on the CLUB equalizer. A CLUB equalizer generally has to be adjusted precisely with the help of a pink noise generator and a real-time spectrum analyzer. It is mainly used to correct and compensate the frequency response of a club. When adjusting it you should therefore make sure that the conditions in the hall match those of the actual listening environment. In addition, adjusting the CLUB equalizer sometimes has to be combined with adjusting the speaker layout.A CLUB equalizer compensates for the frequency response of the environment by changing the frequency response of the signal. Changing the frequency response inevitably changes the phase response and causes phase distortion. When the amount of adjustment made with the CLUB equalizer is too large - especially when a large adjustment is required within a narrow band in order to achieve the desired result - the frequency response of the club is corrected, but because of the phase distortion the sound will be much worse, and this is even more pronounced in a stereo system. When the room acoustics are poor, adjusting the CLUB equalizer sometimes has to be a compromise between frequency response and listening impression. Insisting on a flat frequency response can sometimes backfire. The best approach is to improve the acoustic characteristics of the club itself. Now let us follow Xinzeyu Audio and look at the adjustment process.
1. Adjustment process
(1) Place the measuring microphone at the centre of the hall and set the selector switch on the spectrum analyzer to the "OCT" position (this is the octave filter position, which corresponds to the characteristics of pink noise). The LED display on the real-time spectrum analyzer now shows the frequency response curve of the listening environment. The flatter it is, the better the frequency response of the club's room acoustics.
(2) Feed the pink noise into the mixing console, and set the console to its standard output level, usually 0 VU with an output level of +4 dB. Note that the equalizer (EQ) on the console should be set flat, that is, all bands at zero, neither boosting nor cutting any frequency of the test signal. The frequency adjustment potentiometers of the CLUB equalizer should also be set to zero for the time being. Slowly turn up the amplifier volume control until you can hear the pink noise, and monitor it with an SPL meter until the pink noise inside the hall reaches about 85 dB SPL.
(3) Use pink noise as the system test input signal. This noise is obtained by passing white noise through a -6 dB/oct filter. Compared with white noise, pink noise has more energy at low frequencies. Because the energy distribution of pink noise is close to that of real music signals, it is often used as a test signal in audio engineering and for audio equipment. Pink noise is also generally used to rate the power capacity of speakers. The frequency response of mid-range and better CD players can reach 20 Hz-20 kHz +0.5 dB, which meets the test requirements.
(4) Adjust the boost/cut control for each frequency point on the equalizer so that the frequency response curve on the spectrum analyzer becomes a straight line.
After the above adjustment is finished, you will usually also need to "smooth" the equalization curve on the equalizer. This is mainly to prevent excessive phase distortion when the equalizer is set to a sawtooth-shaped frequency response.
2. Key points for adjusting a CLUB equalizer
(1) In the low-frequency range around 20-50 Hz and the high-frequency range above 14 kHz, do not insist on the frequency response, especially at low frequencies. This is because ordinary speakers can hardly extend down to 20 Hz, and reaching 40 Hz already counts as quite good. Insisting on a flat low-frequency response and boosting the sub-bass will make the speaker run out of control because of the excessive low-frequency extension, and the distortion will get worse.
(2) When adjusting a CLUB equalizer you should always take into account the conflict between a flat frequency response and keeping phase distortion as small as possible, and make a compromise.
(3) Where the frequency response of the room acoustics shows obvious "peaks" and "dips", you should consider changing the speaker positions and trying to change the acoustic characteristics of the room.
(4) Adjusting a CLUB equalizer is very meticulous work and requires repeated adjustment before it can finally be settled. This is because during the adjustment you often also have to make some changes to the speaker placement and the room acoustics, and the equalizer's adjustments interact with one another.
Looked at from another angle, the role of a CLUB equalizer is limited, because the defects of the room acoustics cannot be expected to be solved entirely by a CLUB equalizer. Of course, the smaller the amount of equalization, the better the sound quality will naturally be. If you do not have a pink noise generator and a real-time spectrum analyzer, you can use an audio signal generator to feed the system a signal at each frequency point on the selected CLUB equalizer at the same amplitude, measure the sound pressure in the room with an SPL meter, and then adjust the CLUB equalizer so that the input signal at each frequency point produces the same SPL in the room. Comparatively speaking, the results of this method in practice will be worse than using standard pink noise, so professional users should still equip themselves with a pink noise generator and a real-time spectrum analyzer whenever possible; this will give better results and be more convenient for later use.