Musikality Net

In this article we are going to talk about the various types of EQ, so that those of you who are beginners in mixing, will get a quick grip of what is going on.

First of all, we must understand that equalizers are filters. Their job is to attenuate or amplify frequencies.

Note that in this tutorial we will deal with graphic equalizers, which are the most common VST equalizers. There are other types, especially in hardware forms, but we will not deal with them.

An example can be show in the parametric equalizer in the picture.

Hardware parametric equalizer

Graphic Equalizers allow you to shape the eq curve in a visual way. Most VST equalizers are graphic, even though there are analog simulations which try to emulate the "real" thing. Waves is known for its various emulations of analog gear.

The API 560

The most basic types of filters found in graphic EQs are the following:

High-pass and low-pass

Shelving Filters

Parametric

Notch 

A low-pass and a high pass filter look like that

Low-pass filter

High-pass filter

Low-pass and high-pass filter, are pretty obviously, named like that, because they allow only high or low frequencies in. There are many reasons you’d want that, and usually, when you use an equalizer for mixing purposes, you’ll have one of those in your setting. High-pass filters are used very commonly when you need to mix any other instrument besides a bass, in order to eliminate all the low frequencies, so that you can leave space for the bass. Furthermore, high-pass filters are used to attenuate all frequencies below 30-40 Hz, because they can be a source of clipping and noise in your mix, while they don’t contain any musical material (since so low frequencies can’t be heard very well by the human ear).

Pretty much the opposite applies for low pass filters, even though they are not as common as low-pass filters. Something we must mention for low-pass filters, is that they are used as anti-aliasing filters in the sampling procedure (something which will probably will never bother you ) 

High-shelving and low-shelving filters are called like that, because they create "shelves", as they can be shown in the pictures below. They’re role is to attenuate frequencies, without eliminating them completely.

High-Shelving Filter

High-Shelving Filter

Parametric filters are used to attenuate or amplify a set of frequencies. They are used to "color" instruments in mixes and masters. By attenuating or increasing certain frequecies, you can change the sound in subtle, yet productive, ways.

However, there are times when you’ll meet certain problems in your mix, like pops and glithces from a bad recording, that lie in a very specific range. In that case, in order to remove completely the problem frequencies, you must use a notch filter. These are filters with extremely narrow bandwidth, in order to minimize intereference with nearby frequencies.

Notch Filter

So, that was it! I hope that this little tutorial was some help to you!

This entry was posted on Saturday, January 17th, 2009 at 9:10 am and is filed under Tutorials. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.