A parametric EQ is one of the most powerful tools for mixing audio. In this post, let’s take a look at the settings and controls that you’ll find on a parametric equalizer.
At the end, I’ll introduce you to a trick that will level-up your EQ skills whether you’re a beginner or an expert.
What is a parametric EQ?
A parametric equalizer is a tool for mixing audio that offers control over the frequency, gain, and bandwidth of one or more frequencies.
Parametric EQ Controls & Settings
What you are seeing here is a 1-band parametric EQ. A frequency band is a range of frequencies and this 1-band EQ gives us control over the frequencies in one specified range.
If I add more bands, I will have independent control over more ranges of frequencies. But for the sake of simplicity, let’s stick to just one band for now.
With this equalizer, each band has three main controls: Frequency, Gain, and Bandwidth.
The frequency determines where the EQ band will be centered – this setting is shown in Hertz.
The gain control determines how much the EQ will turn that frequency band up or down. The gain level is measured in decibels, or dB.
Turning a frequency band up is represented as a positive decibel value. Turning a frequency band down is represented as a negative decibel value.
This image shows an EQ set to attenuate (or cut) 1 kHz by 6 dB:
You’ll notice that, although the band is centered on 1 kHz, it is also reducing some of the frequencies above and below 1 kHz.
The bandwidth setting, sometimes called the Q (for quality), determines the width of the band.
This part is kind of counterintuitive at first, so pay close attention here.
This EQ’s bandwidth is measured in octaves. So, setting it to 2 makes the band 2 octaves wide. Setting it to 1 makes the band 1 octave wide. That means the larger the value, the wider the band.
If you’re using an equalizer that has a Q setting, or a quality setting, the opposite is true. The lower the Q value, the wider the filter will be. The greater the Q value, the narrower the filter will be.
EQ Shapes & Filters
So far, we’ve been working with a bell curve shape, but there are other types of filters and EQ shapes that can be found on parametric EQs. Let’s take a quick look at those shapes and filters.
High Pass Filter (HPF)
First, is a high pass filter, or HPF. A high pass filter allows everything above the selected frequency to pass.
These are generally used to clean up tracks by removing extraneous low frequencies.
Because my voice doesn’t contain frequencies below about 100 Hz, I can use a high pass filter to remove those frequencies without affecting the sound of my voice. Once I get into the frequency range of my voice, the high pass filter will start to make my voice sound thin.
I’ll usually start with a high pass filter set just below the lowest frequency in the signal I’m EQing
Low Pass Filter (LPF)
A low pass filter does the opposite – it allows low frequencies to pass.
This can be useful for shaping effects like reverb to make them sound more natural and create space for other instruments in the high frequencies.
When using high pass filters and low pass filters, the bandwidth setting becomes a slope setting. A narrow bandwidth creates a steep slope, while a wide bandwidth creates a gradual slope.
A low shelf is similar to a high pass filter, in that it reduces frequencies below a set point.
The main difference is that a low shelf only reduces it to the specified gain setting, while a high pass filter has a slope that reduces more and more at lower frequencies.
The same similarity exists between a high shelf and a low pass filter.
A high shelf will boost the frequencies above the specified frequency to a specified gain setting.
Band Pass Filter
A band pass filter allows only frequencies within a specified band to pass, while removing frequencies outside of that band.
You can think of a band pass filter as both a high pass and low pass filter working together.
Finally, a notch filter is a very deep cut with a very narrow bandwidth.
This can be helpful for removing microphone feedback, 60 Hz hum, or any other very narrow band noise.
All of these filter types have their place and are useful in different mixing situations, so it’s a good idea to familiarize yourself with what each one does and how to control them.
How To Know Which Frequencies To EQ…
Now that you know how to use an EQ, you may still be asking, “How do I know which frequencies to EQ?”.
By far, the best way to improve your EQ skills is ear training. You can get started with ear training right away with this free Ear Training Frequency Guide or by watching this video: