E.Q. Basics

There are 3 main types of eq curves.
1- Bell
2- Shelf
3- Hi/Low cut filter, or pass filter


1- Bell (fig.3)
The most basic eq curve is called a bell eq, because the frequency curve is shaped like a bell. Looking at the graphic display is very intuitive to see what frequencies are being boosted or attenuated. At any point along the line, you can cross reference the frequency, and the boost or attenuation at that specific frequency.

We also have a parameter called the “Q” which can also be called the bandwidth, and it adjusts how wide or narrow the bell is. You can have a very narrow Q and adjust a specific note, or a wide Q to adjust an entire range.



2- Shelf EQ (fig.4)

When looking at graphic eq display. This EQ curve forms the shape of a shelf. It will boost or cut everything evenly from above, or below a certain frequency.

3- Hi/Low cut filter, or pass filter (fig 3)

The terminology for this category is a bit confusing, because there’s 2 different names for the same thing. Kind of like saying the glass is half empty or half full.
A low cut filter is the same as a high pass filter, and a high cut filter is the same as a low pass filter.

This is cut-off EQ that eliminates all the sound above or below a certain frequency.

A low cut filter (LCF) will have a cut off frequency that everything below that frequency is cut out. Another way of saying the same thing would be to say everything above that frequency can pass, which is why it’s also called a high pass filter, (HPF).

So let’s analyze the wording. A low cut filter will cut the lows. A high pass filter, which is the same thing, allows the highs to pass.

A high cut filter, (HCF) will cut the high frequencies, and a low pass filter (LPF), which is the same thing, will allow the lows to pass.

You’ll often be able to adjust how steep the cut off point is, which is called the “slope”. It can gradually decrease in volume, or it can be a sudden point which drops off immediately. This is measured in DB per octave. To learn what an octave is, check out lesson 9, basic music theory.

The final adjustment available on most EQ’s is a master volume of the output. Often, after you’ve made adjustments with the EQ, the apparent volume will be different. Use the volume knob to counter act this so that the apparent volume remains the same. That way you can do an accurate on/off comparison to hear the effects of the EQ.



Let’s take a look at some various EQ’s.


Fig1- This is a standard digital parametric eq. It is also called fully parametric because it provides full control of the frequency, gain, and Q.

It provides 8 bands, which can be instantiated independently. There’s a low cut filter, a low shelf, 4 bells, a high shelf, and a high cut.


Fig.2- this is a graphic EQ. It has fixed settings for the frequencies. Each slider represents a band, and they can have anywhere from 2 bands to 32 bands. Sometimes, such as in the Pultec in fig.5, each band has several fixed options.

Fig 5- this is a pultec. It is a famous EQ from the 1960’s. It has 2 bands, a low frequency and a high frequency. Each band has a knob to select the frequency, based on fixed points, as well as a knob to boost that frequency, and another know to attenuate that frequency. What makes the pultec special is its ability to boost and cut the same frequency, which creates a great unique tone.


Here are some basic EQ strategies for mixing.

1- low cut filter every track.
Low frequencies do not combine with each other very well, as we demonstrated in lesson 8. For instance, The lowest note of a guitar is the Low E, which is 82 hz. Any vibrations on that track that are a lower frequency than that are unwanted. Vocals almost never have any wanted frequencies below 100 hz, so they should be eliminated.

The low cut filter is my most used tool in mixing. As I demonstrate in the next lesson, on advanced use of EQ, when used properly this can make your mixes clear and punchy.

2- don’t overdo it.
Any descent quality microphone will pick up the sound with a fairly neutral frequency response. While some microphones will have more treble or bass, these differences are generally subtle. Almost all microphones will pick up a nice blend of all the frequencies. If you think you need to tweak the frequency response, there’s a good chance that the issue is with your monitoring or room acoustics. The natural sound of an instrument or vocal is made up of harmonics that cover the entire frequency spectrum, and they will change with each note. Too much tweaking can easily ruin the natural sound.
Don’t add band on top of band, unless there’s a specific reason.
Fig.6 is the EQ curve I use on vocals most of the time. A low cut filter at 150 hz, and a bit of a treble boost, which adds “air”. With a good mic and good room acoustics, you don’t need little tweaks all over the spectrum. If your mic or room acoustics aren’t good, you won’t be able to fix it with an eq, so I don’t recommend even trying. Make your EQ adjustments with intent, knowing exactly why it’s there.

3- in context of mixing a song with multiple parts, avoid soloing tracks to make major EQ adjustments. Soloing for minor adjustments can be helpful, but the overall frequency balance should be done in context of the mix. It doesn’t matter how it sounds by itself, what matters is how it sounds with the entire mix.

4- Use your ears, not your eyes. When adjusting parameters, close your eyes so that your judgment isn’t effected by what you see.