Equalizer Basics and Overview
Proper Equalization can allow music or speech to be heard as it was intended to be heard. If appropriately used, Equalization can improve the intelligibility of a sound system and help with controlling feedback. When starting the EQ process, it is recommended that you always start with “small” changes and remember that too much EQ can make the sound system sound worse than when you started. Whether you are using an Analog or Digital EQ, the functions are basically the same for both.
The EQ shown above is a dual channel 31 band Graphic EQ. Like all other Sound Processors, equalizers can be Outboard (standalone physical units) or Digital (software-based, built into a mixing board, DAWs). DAWs (Digital Audio Workstations) are covered on a different Handout.
Audio Frequency Band / Spectrum notes:
A frequency band is a “range” of frequencies. The accepted and recognized audio spectrum range is 20Hz-20,000 Hz (20kHz). The majority of listeners cannot hear the entire “set” of frequencies in this range, and some of the lower frequencies are “felt” more than they are “heard.” The 20-20kHz frequency range is explained in more detail on Page 24. The Audio Frequency Spectrum range can be divided into groups (see below left).
The screenshot below shows a Frequency Response Curve of an ElectroVoice “Evolve 50M” speaker system. When you adjust an equalizer, you are basically changing the Frequency Response of the sound system. Use Caution.
There are different types of Equalizers (EQs) used in audio systems, but these are the two most popular used in setting up sound systems, monitor systems, and recording. There is more info on the following pages.
Graphic EQs – Use separate sliders for the individual frequencies. Great for live sound, monitor mixes, tuning a room, very easy to set up and use.
Parametric EQs – Allows the user to select, move, and adjust (boost or lower, remove) frequency bands. Most versatile of all the EQ types, and mainly used in music production, studios, live performances, etc.
Graphic Equalizers
Graphic Equalizers can have anywhere between 3 and 31 “sliders” (faders) and each of these sliders will represent certain frequency ranges. The most used variations of Graphic Equalizers are:
- 10 Sliders, One-Octave – Is an Equalizer with 10 Sliders for frequencies on a one-octave basis. The “center” frequencies are one octave apart. Each adjustment you make will affect a whole octave of frequencies. See image on page 34.
- 15 Sliders, 2/3 Octave – Is an Equalizer utilizing 15 Sliders for frequencies in 2/3rd octave increments between bands. See image on page 34.
- 31 Sliders, 1/3 Octave – An Equalizer with 31 Sliders for frequencies in 1/3rd octave increments between bands. Dual 31 Band Shown below.
Graphic EQs are great for live performances, and to identify and remove frequency’s causing feedback.
Graphic EQs are also used for “tuning” a venue. One of the most important points to remember regarding adjusting a Graphic EQ fader (up or down) is that it will also affect neighboring frequencies as well. This type of EQ is usually less expensive than a Parametric EQ, and is the easiest to set up, learn and operate.
The Equalizer above is a Dual Channel 31 band Graphic EQ. If you are using Stereo (Left / Right) outputs from your Mixing Board, the Mixing Boards “Left” output would go to the Channel 1 input of the EQ, and the Mixing Boards “Right” output would go to the Channel 2 input of the EQ. Typically the EQ’s Channel 1 and Channel 2 outputs would feed the Power Amplifiers Channel 1 and Channel 2 inputs.
There are also Digital Graphic Equalizers
This is a screenshot of a “Digital” Graphic Equalizer used in a DAW (Digital Audio Workstation). The above image is from a popular Apple DAW called “Logic Pro.” The big difference is that with an “Analog” Graphic EQ you have to turn knobs or faders to make adjustments, and all adjustments on a “Digital” EQ are made with a Mouse.
Parametric Equalizers
This type of EQ is widely used for recording and live sound and is more “involved” than Graphic EQs. Parametric EQs are more versatile and offer more “precise control” than a Graphic EQ. A Parametric EQ allows the user to control each frequency bands amplitude, bandwidth, and center frequency (control over the Q). You can make gain adjustments and control bandwidth/sloping that affects neighboring frequencies. You get way more control over the equalization of the audio signal than you do with a Graphic EQ. Parametric EQs can take sound board operators and studio engineers years to master. As an audio technician, you need to understand the basic operation/connectivity of a Parametric EQ. This will ensure you’re in a good position to troubleshoot any EQ issues, verify if the EQ is working correctly, and replace the EQ when needed.
This is a screenshot example of a Parametric Equalizer used in a DAW. This screenshot is from the Apple DAW “Logic Pro”
It would be very beneficial for any Audio Technician to do further research and training on as many types of Equalizers as they can get their hands on. Learning how to set up a sound system and be able to “EQ” and “Tune” a room (system) would also be a “valuable” skill set to acquire. The more you know, the more indispensable you become to your team, job, and boss!
