Equalizer
An equalizer or EQ (also: Equalizer, English: to equalize , to equalize : to adjust, equal : equal) is a filter as an electronic component for sound design and for equalization of sound frequencies, mainly music, or other frequency-based signals such as modulated data signals. In German, this term mostly refers to the devices or plug-in described below . For other meanings of the English term, see equalization .
Designs
An equalizer consists of several filters with which the spectrum of the input signal can be processed. An equalizer is commonly used to correct for linear distortion in a signal . A distinction can be made between different design and operating concepts.
- Graphic equalizer
- Each frequency band that can be influenced is assigned its own controller (as an independent device, it has 26 to 33, typically 31 frequency bands, each 1/3 octave wide), so that the course of the frequency correction is displayed “graphically” by the controller. This type of equalizer is also called an x- band equalizer. The x stands for the number of controls (with 31 controls as 31-band equalizer). Smaller graphic equalizers (approx. 2–10 channels) are used as tone controls in some power amplifiers.
- Parametric equalizer
- The center frequency and the change in amplitude (semi-parametric equalizer) and often also the filter quality Q (according to the bandwidth ) can be set here for one or more frequency bands (fully parametric equalizer). This design can be found mainly in mixing consoles and effects devices .
An equalizer (a filter) is usually actively integrated into the negative feedback in the amplifier or is passively connected upstream of an amplifier.
Digital filters , which are implemented as algorithms in programs for audio processing, are becoming increasingly important . Computers or digital signal processors (DSPs) are used.
use
Hi-Fi
Equalizers are used in hi-fi systems to adapt their sound to your own requirements or the room acoustics .
Concerts and events
At concerts , in addition to equalizing individual signal sources (channels), equalizers are primarily used to adapt the overall sound of the PA system to the location. The reason: Every room influences the sound image due to its geometry . By reflecting the sound waves on the walls, frequencies are amplified and / or attenuated ( interference ). These "bumps" in the overall frequency response of the system and the room are "leveled" with the equalizer (during the sound check ). To this end, the equalizer in the so-called "sum" is (audio output at which is present the total signal) looped .
Sometimes spectrum analyzers are used for this , which measure the acoustic properties of the room and the equalizer and possibly other devices for influencing the sound system, e.g. B. specifically set crossovers or delay elements (integrated hardware / software solutions). As a rule, however, fine-tuning by an experienced sound engineer or sound engineer is preferable, if necessary with the support of spectrum analyzers. Especially in large concert halls with possibly many sound sources (since a large volume has to be exposed to sound ), the sound of the concert is very much dependent on the correct setting of these components.
Monitoring
In order to avoid annoying feedback when monitoring live concerts , equalizers are often looped into the signal path of the monitoring system, thereby lowering the frequencies concerned. This can also be done semi- or fully automatically using so-called feedback destroyers . In the semi-automatic process, the device searches once for the frequencies that are causing the feedback and saves the setting. With the fully automatic method, problematic frequencies are constantly searched for during the concert and these are reduced in a narrow band, as they can change constantly (e.g. due to different microphone positions when the singer moves).
Both methods allow a higher monitoring volume, with the fully automatic one having a greater effect. The disadvantage here, however, is the constantly changing frequency response of the monitor system, which can disturb the sound impression.
Sound design
At concerts or in the recording studio , the individual audio signals are equalized using an equalizer (e.g. in the event of acoustic problems during recording or the non-linear frequency response of devices and microphones) and adapted as a sound effect to the taste preferences of the sound engineer / music producer . Care is also taken to ensure that the individual signals are processed in such a way that they fit harmoniously into the overall mix (e.g. by highlighting different characteristic frequencies of two similar signals, e.g. electric bass and bass drum ). In addition, EQs are used for extreme signal changes in order to be able to limit the processing by downstream devices to certain frequency ranges, which are then mixed back into the sum, or to be able to explicitly frequency control effects via a detector input (key chain) ( Examples: De-esser; Phaser on drum track).
Parametric equalizers with a large effect amplitude and high filter quality are also used directly for sound design. The flowing change in the "cutoff" frequency results in characteristic, often artificial-looking pitches and resonance courses that can range from sawing to chirping.
DJ
Even DJs use equalizer in the DJ mixing consoles (also called mixer) are integrated. These equalizers are often much simpler. The most common variant here is the DJ mixer with a three-band equalizer and a maximum level reduction of 32 dB. This is mainly due to the fact that the equalizer is operated in live mode and should therefore be kept as simple as possible to ensure quick operation. They usually do not consist of sliders ( faders ), but are provided with rotary controls.
Names and other examples
Examples of filters in sound engineering:
- Treble lock / treble filter / high cut / treble cut for strong attenuation ( to cut = to cut off) the high frequencies; (academic: low pass ) and
- Deep lock / bass filter / low cut / bass cut / low-cut filter / rumble filter for strong attenuation (English: to cut = to cut off) the low frequencies; (academic: high pass ).
- Parametric or semiparametric filter / bell filter for the bell-shaped (English: bell = bell) change of a frequency band around a base frequency (English: center frequency ). With semi-parametric equalizers, only the base frequency can be adjusted, with (fully) parametric EQs the slope (Q) can also be adjusted.
- Notch filter (English: notch = notch) for influencing (usually lowering) a narrow frequency band by means of a steep-edged filter; (also called "kill filter"). This type is mostly used to remove background noise or acoustic feedback as well as to influence the sound by DJs and represents a special case of the bell-shaped parametric equalizer with extreme slope.
- Shelving / Hi-Shelf / low-shelf filter as open on one side for lifting / lowering of ups and downs.
There are also the most important filters for sound design (for sound design): the presence filters and absence filters . This includes the bathtub filter known in the sound engineering jargon , which is mainly used to "clear out" "unclear" sound recordings.
literature
- Roland Enders: The home recording manual. 3rd edition, Carstensen Verlag, Munich, 2003, ISBN 3-910098-25-8
- Rolf Beckmann: Manual of PA technology. Basics, components, practice. 2nd Edition. Elektor-Verlag, Aachen 1990, ISBN 3-921608-66-X .
- R. Bücklein: Audibility of irregularities in frequency responses in acoustic transmission. Frequency, Vol. 16, No. 3, 1962, p. 103 - Dissertation 1964, TH Munich.