Equalizers are used to mix the input channels and the wiring equipment of the mixer, for example, on the output line leading to the speaker. Although the use of equalizer in microphone input channel reminds us of its method of shaping the sound of speakers or musical instruments, the question that is often overlooked is whether an equalizer is needed, which may be a sign of errors in other links.
Equalization can be used to compensate for problems in audio link or speaker audio characteristics, microphone selection or studio acoustic influence. It may even appear in a recording studio with perfect acoustic characteristics, the latest speakers and the best microphones.
It is particularly interesting to use an equalizer in the output channel leading to the loudspeaker, because it is easy to mistakenly think that it can solve all the improper room acoustics and loudspeaker sound reproduction problems. Two equalizers are used: parametric equalizer and graphic equalizer.
Measurement and correction characteristic curve of frequency doubling equalizer.
The above curve is the total response of the three filters, which is set to +6dB, and the center frequencies are 630, 1250 and 2500Hz. The curve below is the same frequency doubling filter set at +2dB.
The parametric equalizer can correct the sound signal and independently control the gain or attenuation of filtering frequency, bandwidth and amplitude. The frequency and peak amplitude or valley value in each frequency range can be adjusted continuously or step by step through potentiometers and switches. Operators can adjust the frequency range of 20: 1 and at the same time adjust the definition or peak bandwidth, which is the so-called quality factor (Q value), and its value is 0.29 ~ 5.0. Generally, the highest and lowest frequency ranges can be switched from peak form to flat form.
The equalizer shown in the figure can usually correct the shape of sound signals in a fixed frequency band of 8, 12 or higher. Each frequency band has its active filter, and the center frequency of the filter is specified near the potentiometer used to adjust the correction amount (in dB). If the frequency band is divided into octaves, the equalizer is frequency doubling, using fewer frequency bands (filters). 1/3 frequency multiplier equalizer has more frequency bands, for example, 3 1 filter (center frequency 20 Hz ~ 20 kHz), which allows more accurate but more complicated correction than frequency multiplier equalizer. The available correction amounts are usually one channel 15dB or two channels 15dB respectively. When setting the sliding calibrators, they will form a graphic curve with a shape corresponding to the selected calibration curve. This is the origin of the name "graphic equalizer".
When the equalizer is used to correct insufficient acoustic characteristics or speaker sound return characteristics, the operator can set the calibrator subjectively "through the human ear" or objectively using the audio analyzer. The microphone of the analyzer acts on the sound wave at the measurement position, and the calibration pattern shape of the calibrator is set to be opposite to the measurement shape, so that the generated characteristic curve is as linear as possible. But all this only applies to one point in space.
Because the ear of the operator and the microphone of the analyzer record the response characteristic curve of the speaker at one position, this may cause problems when the operator moves to another position. All the settings of the equalizer in a certain position are not suitable for any position except the place where the microphone is placed. In addition, considering the complexity of the sound field in terms of acoustic standing waves and indoor ringing modes, and the ratio of direct sound waves to reflected sound waves in a more or less diffused acoustic space, it is easy to understand that the balance that produces a slightly improved response at one location is not as good as the balance that produces problematic results at all other nearby locations. The human ear separated by the skull (the average distance is 19cm) is very sensitive to the diffraction of sound waves around the head, so that we can feel the direction, intensity and time difference of direct and reflected sound waves. This is binaural hearing. In all cases except using the dummy head (the microphones are placed in the exact positions of the left and right ears), due to the subjective nature of hearing, single-tone microphones and even overlapping stereo microphones will provide the analyzer with completely different objective data from what the audience hears.
The measurement and calibration characteristic curves of 1/3 frequency doubling equalizer set at +2, +4, +6, +8,+10 and+12dB respectively.
However, even if the analog head and the measurement method with good subjective feeling correction are adopted, it is worth remembering that any correction in a frequency range may lead to bad effects in a more or less large range, depending on the type of equalizer. Figure 1 and Figure 2 show this situation. Obviously, the frequency multiplier equalizer (Figure 1) has wider correction characteristics than the 1/3 frequency multiplier equalizer. This is determined by the characteristics of the equalizer.
However, even when the corrector is set at the highest position (+12 or+10dB), the 1/3 multiplier equalizers have quite narrow characteristics, and they will have wider characteristics at +4dB. As for the "narrowband" 1/6 octave equalizer and1/0 octave equalizer, the greater the potential of the equalizer, the more ways to achieve unusual, exaggerated and artificial sound effects.
Therefore, it is very important to balance with a cool head and be as rational and logical as possible.