Equalizer (English equalize – “equalize”, the general abbreviation is “EQ”), a timbre block is a device or computer program that allows you to increase or decrease the volume of individual zones of the frequency range, equalize the amplitude-frequency characteristic of the sound signal, that is, adjust it (signal) amplitude selectively, depending on frequency.
Born in the 30s, the equalizer is the oldest and most commonly used sound processing by sound engineers. Today, the market lacks a variety of instruments for timbre correction – from a simple bass-treble corrector of the 50s to a sophisticated multi-band equalizer with perfect parameters. At its core, the equalizer is a few electronic filters that allow you to change the amplitude-frequency response of a sound device. Over the past half century, the equalizer circuitry has improved tremendously, trying to satisfy the increased demands of the audio industry.
First of all, equalizers are characterized by the number of frequency filters (bands) that are adjustable in level. Initially, equalizers were used in accordance with this definition: during the first recording experiments, the studios were equipped with low-quality microphones and speakers that distorted the source material, and the equalizer was used for its frequency correction. However, today the equalizer is a powerful tool for obtaining a variety of sound tones.
The process of processing an audio signal through an equalizer is called “Equalization”.
Equalizers can be found in both household and professional audio equipment. Equalizers are included in many computer programs related to the reproduction and / or processing of sound – various audio and video players, editors, etc. Many electro-musical instruments, instrumental combo amplifiers and effect pedals are also equipped with equalizers, although less functional.
Equalizer is the most used device in the audio industry. Just understanding its essence, an audio engineer can competently manage it and get the result that he achieved. The key to understanding the essence of timbre correction is understanding how to achieve the result you need. It is equally important to know the features of the microphones used or the possible problems associated with their placement. The equalizer is not a panacea, it does not know how to correct errors – it just helps to highlight the signal with which you will work further. It copes much better with the task of cutting off the unnecessary than with the task of extracting from the signal something that does not exist in it.
There are two main types of multi-band equalizers: graphic and parametric. The graphic equalizer has a certain number of frequency bands adjustable in level, each of which is characterized by a constant working frequency, a fixed band width around the working frequency, and also a level adjustment range (the same for all bands). As a rule, the extreme bands (the lowest and highest) are “shelf” type filters, while all the others have a “bell-shaped” characteristic. Graphic equalizers used in professional areas usually have 15 or 31 bands per channel, and are often equipped with spectrum analyzers for easy adjustment.
The parametric equalizer provides much greater possibilities for adjusting the frequency response of the signal. Each strip has three main adjustable parameters:
– Central (or working) frequency in hertz (Hz);
– Quality factor (the width of the working strip around the center frequency, is indicated by the letter “Q”) – dimensionless quantity;
– The level of gain or attenuation of the selected band in decibels (dB).
Thus, the user can more accurately select the desired frequency and adjust it more precisely. Analog parametric equalizers are quite rare and have a small number of adjustable frequency bands. However, advances in digital processing of the audio signal contributed to the emergence of digital parametric equalizers with an almost unlimited number of adjustable frequency bands. Very often, parametric equalizers can serve as one of the processing units of digital acoustic processors. Moreover, in digital parametric equalizers, there are often additional band parameters, such as: filter type, curve nature, etc.
There are mixed-type equalizers that can be found in mixing consoles, where, for example, low and high frequencies are regulated by the type of graphic equalizer of the “shelf” type, and between them there are two semi-parametric bands (without Q adjustment).
There are also hybrids called “paragraphic” – it is a graphic type equalizer with Q-factor adjustment.