An EQ or equalizer is designed to add or remove frequencies of the audio spectrum. Certain EQ’s can be more precise than others, allowing you to eliminate problematic frequencies surgically. Others will add or remove wider frequency bands that allow you to be a little more aggressive with the processing. One essential part of an equalizer is the filter shapes, and it’s important to know when, how to apply them and for which tasks. In the next tutorial, we will cover the most important filters using a parametric equalizer.

We have chosen this type of EQ since it’s probably the most common, and its graphic interface makes it easy to see what part of the frequency spectrum we’re processing. For this tutorial, we created a track in our SoundBridge: DAW.

Track for applying filters in EQ

First, let’s look at the LOW-END GROUP within our project. It contains elements that occupy the lower part of the frequency spectrum, such as the kick drum, bassline, etc. This would be a perfect place to apply a “low cut filter”.

~Low End Group – Unprocessed

Low end filters

We have chosen the FabFilter Pro Q 3, for this task, but there are lots of other alternatives out there, so feel free to explore. We will place an instance of this plugin on the effect rack of our LOW-END GROUP, and apply a low cut filter.

Low cut filters

You can see in the image above that we have several EQ controls: Gain, Frequency, Bandwidth, and Slope. In the case of a low cut filter, the frequency control determines below what frequency there will be attenuation, while the Slope control determines its amount.

This sort of filter is also referred to as a high pass because it lets through all high frequencies above a cutoff point. The low cut filter is most commonly used to eliminate unwanted or problematic low frequencies. As you can hear from the audio example below, it’s also possible to automate the frequency parameter and generate a sweeping effect.

~Low End Group – Low Cut Filter

The next EQ filter type we’re going to cover is the low shelf. Unlike the low cut filter, a low shelf doesn’t cut frequencies out exponentially. Instead, it reduces or boosts all frequencies by the same amount below a cutoff point. In this case, we have applied it to the PERCUSSION GROUP within our track. Let’s hear how that sounds before and after processing.

Low shelf filters
~Percussion Group – Unprocessed
~Percussion Group – Low Shelf Filter

High end filters

Moving forward, we have a high cut filter, which behaves exactly like the low cut filter but affects frequencies above a cutoff point. As you can hear from the audio example below, we’ve used it on the DRUM GROUP, and it can also be used to generate a sweeping effect by automating the frequency.

Hi cut filters
~Drum Group – High Cut Filter

Likewise, a high shelf filter attenuates or boosts frequencies by the same amount above a specified cutoff point. We will apply it to the Ac. Guitar channel. Let’s listen to the before and after.

Hi Shelf filters
~Ac. Guitar – Unprocessed
~Ac. Guitar – High Shelf Filter

Bell and notch filters

A bell filter boosts frequencies around a specified center frequency point. On the other hand, a notch filter attenuates them. The bandwidth or “Q” sets the width for either filter curve. Bell curve filters are also known as peak filters, while notch filters are also known as bandstop filters.

This filter type can be used with precision to boost or reduce any range of frequencies.

We’ve used bell and notch filters to boost and attenuate specific frequency ranges as you can see in the picture below. Let’s hear how our full mix sounds before and after applying this processing.

Bell and notch filters
~Full Mix – Unprocessed
~Full Mix – Bell & Notch Filter

Bandpass filter

Finally, the Band Pass filter allows through a range of frequencies around a specified center frequency point. Low and high frequencies outside this range are attenuated. This filter type can be used to isolate a range of frequencies, and also, with the help of automation, create sweeping effects.