A Basic Understanding of Equalisation

What Equalisation is and How to Begin Utilising it

EQ is a tool that mixing engineers use to help balance a track in the mix. An EQ allows you to boost and reduce frequencies of a certain track, this could be to eliminate unwanted or unused frequencies or to put emphasis on desired frequencies. EQ's can be in software or outboard form and many mixing consoles have at least some level basic EQ control on each track. Although there many different forms of EQ, such as fixed and graphic which wont be touched upon in this post, they all do the same job. 

Understanding the Graph on a Parametric Equaliser

Although an EQ's graph may look confusing it is easy to understand. On the X axis runs frequency (Hz), usually only through the human hearing scale and on the Y- axis is dB. An increase of dB boosts the frequency and vice versa.

The Basic Parameters of a Typical Parametric Equalisation Unit

In order to fully understand how to operate an EQ, the parameters must be explained. In the image above is Pro Tools built in Parametric EQ unit, although visually different to others the basic controls stay the same throughout all EQ's. The first basic controls at the top are input and output, these simply control the level the track is when it goes in and its level when it leaves the effect. After this we arrive at HPF and LPF, these stand for high and low pass filters. Applying a high pass filter to a track would only let the high frequencies through, this is assuming it is on the highest dB Q and vice versa for low pass. You can control the amount of filter both the frequency and Q controls.

Frequency on a high or low pass filter controls up to which frequency the filter will effect. This is seen in the image to the left.














After the frequency control has been chosen the 'Q' controls how steep a roll off the filter has. (How quickly from the selected frequency does it completely stop sound passing).

Underneath the HPF and LPF controls are the parameters to go into greater detail in frequency manipulation. All these five parameters have essentially the same controls. Pro Tools just assign different colours and controls to different frequency groups so editing can be done to multiple parts of the frequency spectrum and the controls are not easily confused. In this example I am going to use the LMF parameter (low mid frequencies).


Frequency, again controls the specific frequency you are aiming to target.

The orange dot swivels across the spectrum to identify the chosen frequency.

The gain controls the boost or cut to the frequency, positive being boost and minus cut.



















Then finally Q in this instance controls how accurate the boost is, how many frequencies it will effect. 10 is the most accurate and 1 is the least.

Important Things to Note: This is only a guide to the very basics of EQ and is only aimed at giving a quick overview of the effect. Kinds of filters, such as shelving and peaking and their creative uses will be explained in a pending post. In addition, as already explained other soft parametric EQ's may differ in appearance and structure but the fundamental parameters will be the same.