Everyone has used an Equalizer (EQ) at some point in their life. Something as simple as adding bass to your car stereo is an EQ move. Understanding EQ allows you to add character and color to your recordings and help bring out the best in your tracks!
Let's Get The Basics
An equalizer is a building block of the audio chain and is probably the most important! Before we dive into using an EQ, lets learn more about what the EQ spectrum is. The EQ spectrum can be broken down into 4 parts: Lows, Low-Mids, High-Mids, and Highs.
This is pretty self explanatory, but let's look deeper. The lows stretch from below our hearing through past 200Hz. This is the frequency spectrum you would associate with kick drums and bass. Next, the low-mids, stretch from around 200Hz to 2kHz. The high-mids stretch from around 1 to 7kHz. These ranges are critical for many instruments, including guitars, winds, strings, and vocals. Our ears are tuned into these frequencies and many of our instruments will dominate this space. Finally, the highs range from 6kHz and up beyond our hearing. This is what gives a song space, air, and sparkle.
The chart above is a great tool for learning what each frequency range does. As you can see, each range can be excessive, deficient, or developed. For example, if you are recording your acoustic guitar and notice it sounds a little dull compared to other recordings, a good place to check would be the highs, specifically around 5-8kHz. Another common problem is that a home recording will sound boxy, meaning there is an abundance of frequencies in the low-mids.
I Got It. How Do I Do It?
All DAW's will have a stock EQ that are pretty good. While they might look a little different, they will all include several bands, gain, type, and Q.
Bands:
The EQ band is the area that will be affected by the EQ move. Looking at the image above, we can see the red band is set at 50Hz, orange band at 300Hz, yellow band at 500Hz, and green band at 3kHz.
Gain:
Gain is the amount of decibel change. The orange, yellow, and green bands are cut by around 3dB each, while the red band is boosted by 2dB. We can see this change in the dials and the graph.
Type:
There are 5 basic types of EQ Types: Low pass, Low Shelf, Bell, High Shelf, and High Pass. The Low Pass and High Pass EQ's remove frequencies below or beyond the selected point respectively. Shelving EQ's can boost or cut at a specific frequency and beyond. Finally, the bell EQ creates a bell curve to boost or cut a frequency.
Fig. 1 shows a low pass and high pass filter.
Fig. 2 shows a low shelf boosting at 80Hz and a high shelf cutting at 5kHz.
Fig. 3 shows multiple bell EQ curves.
The Q:
The last part you'll see in most EQ's is the Q, or curve of the EQ. This is most clear in the image above. We see both the yellow and green EQ curves are very gradual and have a soft slope. These have low Q numbers. If you look at the blue EQ curve at 2.5kHz, this has a higher Q (3.20) and you can see that the slope is much more extreme.
Hardware vs. Software
There are pros and cons to choosing a hardware or software EQ. For many of us, we will not have access to a hardware EQ unit, so software options will be our focus here. As you can see above, the hardware EQ is more limiting than a software option. The EQ types are fixed, there is no visual representation of what's going on, and (in this case) the EQ dialed in will be added to the recording and cannot be changed later.
If you are new to recording or a long time engineer, software EQ's can and have become a powerful tool in the toolkit!
Different Types of EQ's
Graphic EQ:
A graphic EQ uses sliders based around a specific frequency to make changes. These can be very powerful but have limitations because EQ points cannot be changes and Q curves are fixed.
Parametric EQ:
These EQ's are most common in today's workflow. The Pro Tools 7 band EQ and the Logic Pro X stock EQ are both examples of the parametric EQ. These are very customizable and have the ability to use all the EQ types.
Dynamic EQ:
This EQ reacts to the dynamics of the frequency fed into the EQ. This EQ is very powerful and often seen in end stage mixing and mastering.
Putting It All Together
The best way to learn about EQ is to use it! One of the techniques engineering school taught me was the sweep method. Pull up an EQ and create a bell boost. Slowly move the bell up and down the EQ spectrum. How does it affect the sound of the source? Does it sound better with the bell up, down, or disengaged? With enough practice, you'll be able to hear a recording and know how to change the EQ in order to make it sound even better than it was before!