In this article you will learn what an equalizer is, what it is for and what types of equalizers exist.
An equalizer is an analog or digital device designed for amplitude-frequency correction of a signal. It is a device consisting of several frequency filters. This allows you to change the level of different frequency ranges depending on the filter settings.
The first equalizer appeared in the 30s of the XX century and was used for sound correction in the film industry. The initiator of the use of this device to improve the sound was John Volkman. This device was a block consisting of two sliders, each of which had a frequency selection switch. This device was called EQ-251A. Further experiments with the use of equalizers continued, and in 1967 a device consisting of a set of passive 1/3 octave filters was developed. This device was called “Acousta Voice”.
After this invention, equalizers began to be used everywhere and their development continued exponentially.
At the moment, the film industry and sound engineering uses a large number of different types of digital (software) equalizers, which are a plug-in or program that is installed on the computer and uses its resources for signal processing.
The process of signal processing by EQ is called EQ.
Equalizer settings
The main parameters of the equalizer include:
Number of EQ bands (number of filters used) – 4-band EQ; 10-band EQ, etc.
Cutoff or Freq-filter cutoff frequency or center frequency (frequency of the selected EQ node); units – Hertz (Hz).
Q-factor or resonance (Q or Res)– bandwidth (number of affected frequencies around the Central frequency); units – conventional units.
Gain level – the level at which the frequency band around the center band will be reduced or increased; units – decibels (dB).
The slope – the slope of the curve of the cutoff frequency when using cut or shelf filter types; the unit of measurement is decibels per octave (dB/Oct.).
Often virtual equalizers (VST plug-ins) have the ability to change the type of filter for each node. Analog equalizers have fixed filter types. Such devices are usually equipped with several bell-shaped (peak) and two cut filters (Low Pass and High Pass).
Types of equalizers
By type of control equalizers are divided into graphic and parametric.
Graphic equalizers have several frequency filters with fixed Central frequency and q-factor, as well as with the same maximum level of attenuation / gain for all nodes. Currently, this type of equalizer is rarely used.
Parametric equalizers have several frequency filters with the ability to change the Central frequency and q-factor of each. In addition, modern models of virtual equalizers have the ability to add an unlimited number of filters, the type of which can be changed. Parametric equalizers have gained popularity among sound engineers, producers and musicians due to the flexibility of their settings.
There is an intermediate type of equalizers-paragraph equalizers.
According to the principle of operation equalizers are divided into phase-shifting and linear phase. Already from the name it is clear that the first affect the phase of the signal, and the second – no. Both phase-shifting and linear-phase equalizers have their advantages and disadvantages.
The advantage of linear phase equalizers is the absence of phase shift after processing, and the disadvantage is a much greater load on the system (in comparison with phase – shifting equalizers) and smoothing the attack of the processed signal.
The advantage of phase-shifting equalizers is their lightness (in terms of load) and the fact that they do not affect the signal dynamics (the attack phase remains unchanged). The disadvantage of this type of equalizer is their effect on the phase, which can lead to a change in the balance of the mix (if the equalizer is used when mixing on one of the tracks of the mix).
The main tasks of equalization are:
– Correction of the amplitude-frequency characteristics of the signal due to distortion caused by the shortcomings of analog recording or processing devices, as well as the characteristics of the room;
– Removal of “bad” (unwanted) frequencies;
– Elimination of resonances caused by various factors (the presence of reflections from the walls of the room, the vibration of the instrument body, the wrong location of the pickup when recording, wrong synthesis);
– Elimination of frequency conflicts (mixing tools in the mix);
– Artistic equalization.
At the moment, the most popular in my opinion VST Eqs are FabFilter Pro-Q2 and I am satisfied with the standard Fruity Parametric EQ 2 of FL Studio
