We recently talked about EQs (Tools: Equalizers) and left a door open to talk about filters.
Filters are usually considered part of the EQ. Pretty much every EQ has filters, but they have particular importance when mixing. This is why I've decided to dedicate them to a specific article.
Type Of Filters:
There are two kinds of filters: HPF and LPF.
HPF stands for High-Pass Filter and is sometimes called a low-cut filter - if you think about it, the concepts of high pass and low cut are the same. As the name states, it cuts the low frequencies while letting the high frequencies pass through.
LPF stands for Low-Pass Filter and is sometimes called a hi-cut filter. Again, the concept behind the two names is the same. This filter cuts the high frequencies while letting the low frequencies pass through.
Slope: Without being too academic and pedantic, the slope determines the drop in dB per octave of the filter and expresses how aggressive the filter is. For example, 6 or 12 dB/Octave is considered a soft slope, so the filter is not too aggressive. An average slope is usually 18-24 dB per octave. A hard slope is 32-48 or more dB per octave, and the filter reacts in a very aggressive way.
When Use Filters:
We use filters to clear out unwanted frequencies and create space for other instruments.
It’s common to filter out the low end of instruments to create space for kick and bass.
It is also common to say that these filters cut the low or the top end, but what they actually do is attenuate those frequencies.
How To Use LPF/HPF:
Using these filters is very easy:
Activate the filter on the desired instruments.
Cut until you can hear the filter affecting the sound.
Go back a bit to play in a safe zone.
Trick:
The busier the mix, the more aggressive the slope should be to clear out unwanted frequencies and create more space.
Consider:⠀
6-12 dB per octave = soft slope⠀
18-24 dB per octave = normal slope⠀
32-48 dB per octave = aggressive slope⠀