Believe it or not you have been using an equaliser all your life. Every time you turn the volume knob on your stereo system you are in effect using equalisation. A gain knob is sometimes referred to as a single band gain control. BUT, even more common are the equalisers provided with stereo systems that can be used to refine the sound to the listener's tastes. In the studio we take this many steps further as we need very specific tools for specific tasks and a single all encompassing equaliser might not be enough.
Separating the frequencies of instruments by the use of EQ is a traditional, yet subtle, method of creative and corrective EQ.
In fact, this method is not limited to the mix and production stages but is also prevalent at the tracking stage. There are many instances whereby EQ has to be used to compensate for a poor microphone (or it’s use in a given environment) or a poor room (poor acoustics resulting in boomy, resonant, ringing etc anomalies).
EQ is also used in live situations to compensate for the environment, the singer, the microphone, background noise, colour and so on.
What is an equaliser (EQ)
To define what equalisation is would take quite a while but a condensed definition would be:
A dynamic processor which uses filters to alter the balance of frequencies in a sound.
This is achieved by using a number of filter circuits, which apply positive or negative gain to selected frequency ranges. The positive gain is referred to as ‘boost’ and the negative gain is referred to as ‘cut’.
Corrective or Compensatory eq
Actually the first ever instances of equalisation was in the communications industry. EQ was used to counteract some of the problems in telephone systems. It then transgressed into the broadcasting industry.
Tone controls were created and used to compensate technical inaccuracies in the recording chain, more notably, compensating for microphone colouration and room acoustics. EQ was used as a means of controlling the gain of a range of frequencies.
This form of equalisation is termed as ‘corrective or compensatory’ EQ.
We use the same principles when using equalisation to remove problematic or redundant frequencies.
Creative equalisation is used to ‘colour’ a sound or to reshape it’s characteristics to create a new sonic texture (boosting the mid-range frequencies of a kick drum to accent the punch and body is a good example). This is where we get creative and reshape sounds to suit the mix. Sometimes we use minimum phase designed equaliser that impart a ceratin colour on the sound.
Redundant frequencies can be visible when using an equaliser with a graphical display but the important distinction here is that we cannot hear them. Any frequency that is visible but not heard is regarded as redundant - in that we don't need them.
In the video I explain everything you will ever need to know about how an equaliser works and how to use it. All of the equaliser's features are explained and demonstrated. I show you how to read the GUI of an equaliser and how to use the various filter shapes to eq any sound. I walk you through each type of filter including high pass, low pass, band-pass, notch, shelves and so on and using audio examples to demonstrate how each type behaves.
Topics covered in this video are:
What is equalisation and how does it work
Band, Q and Gain
Fixed versus Peaking
Cut versus Boost
Phase - Minimum and Linear
Slopes and Gradients
Octaves and Frequencies
Dynamic versus Static/Passive