Filters are a great way to mould a sound to where you want it to be. With one setting you can dramatically change a sound from big and bright to small and soft. Knowing how to use filters to get to where you want can be an excellent tool.
A filter in audio, does what it says, it filters the frequency spectrum of a sound anywhere from removing the low end, removing the high, removing both to leave the middle or removing just the middle. A filter can do it all!
Using filters you can seamlessly transform a sound, clean audio up, or create cool effects like radio vocals, just by taking away everything but the middle. You can hear this effect in a recent mix I did for Gus Harrower in "The Usual"
There are four main filters to know about, each one with their own shape for particular purposes:
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The First is a High Pass Filter, also referred to a low cut. This comes standard on most mixing desks as it is super simple to filter out unwanted low end rumble. As you can see on the image below, the EQ Curve lets the high pass through but cuts the low.
The second is the opposite of the High Pass Filter, called a Low Pass Filter, also known as a high cut. This shape allows the low to pass through while the high is cut. Particularly useful if you have a big bright sound you want to be soft, warm and subtle.
The third filter is known as a Band Pass Filter. This only allows a certain frequency band through and is effective in creating a "radio voice" tone by band passing around 1 khz. As seen below only the frequencies in the chosen band are unaffected.
Lastly we have the opposite of the band pass filter, known as a Notch Filter. This allows everything but the chosen Frequency to pass through. As you can see in the image below, it is helpful in cleaning up frequencies in the middle of the spectrum, or in creating a hollow sound.