Equalizers can show up in many different forms in your home recording studio.
They can be found as part of your hardware or software based mixing console, on your instrument pickups, or even as stand alone units.
So what is the purpose of equalization, or EQ?
It allows you to have precise control of your sound by changing the balance of specific frequencies.
That sounds nice but why use EQ in your recordings at all... you may be asking yourself.
The reality is that although you do everything you can to make your raw sound as musically balanced as possible, there is rarely a recording that can't be improved with some (slight) tweaking.
Like any signal processing or effect, a little goes a long way - and a lot can ruin a track that had some potential.
So with that in mind let's look at the different types of EQ you might run across.
Shelving EQ - These are the type that most people will be familiar with.
This type of equalizer boosts or cuts the signal at pre-determined frequencies.
On my Mackie Mixing Console, the HI, MID, and LOW shelves are set to 12kHz, 2.5kHz, and 80Hz respectively.
So if I want to cut the gain of a signal at 14kHz then I use the HI settings.
The downside is that this cut also affects everything greater than 12kHz( i.e 15kHz, 16Khz,etc.) all at once.
To tweak more precisely we'll have to look to a different Equalizer type.
Highpass / Lowpass Filter EQ - The name of this one says it all.
The highpass filter allows high frequencies to pass through while cutting low frequencies below a designated threshold. Lowpass filters do the opposite, cut high frequencies while low pass through.
Unlike a Shelving EQ, these will give a different attenuation (cut or negative gain) to frequencies based on how far away they are to the cutoff point. So the further away a frequency band is from the operation point will be cut by a greater amount.
Graphic EQ - This is by far the coolest looking feature of any equalizers. It has several sliders all corresponding to a certain frequency bands (usually 15 or 31).
The more sliders you have, the more control you have over your sound since you can tweak and adjust with greater precision. Each slider represents a notch filter that can be used to adjust that specific frequency band.
Notch Filter EQ - This type of EQ is particularly useful for live performing applications. It works by cutting a band of frequencies around a specified band while leaving those frequencies higher and lower unaltered. This helps in eliminating feedback at the specific frequency band where it originates.
Parametric EQ - This type of EQ is very useful because there are 3 values that you can adjust as needed: Amount of boost (or cut), the center frequency, and width of frequencies (called bandwidth or Q).
You can think of a Notch Filter as a specific application of this type of EQ. A wide bandwidth will have an affect on the overall sound, while a narrow bandwidth will zero in on a specific tone.
Equalizers come in both hardware and software versions.
When talking about signal processors remember that hardware versions run on dedicated circuitry while software versions will use some of your DAW's resources.
The software versions are slick because they can save settings (useful for Graphic EQ's) but hardware versions free up your DAW's processors...
so it's a trade off that you'll have to consider.
Personally, I feel like the software based equalizers contained in today's digital recording software packages is more than sufficient, and far more desirable than adding another piece of gear to the setup.
As is the case with the compressor the learning curve on these is steep, but once you become more comfortable using it the equalizer can be another valuable tool to have in your home recording studio.
Get in the habit of switching between the Equalized and raw original sound to train your ears.
Sometimes the best thing you can do is leave the track alone... and this is a good thing.