As I covered in my overview of the types of EQ filters, there are a number of different ways to cut or boost different sections of your audio’s frequencies. We’re going to focus on the low shelving filter here, covering what it is and when to use it in your mix.
Low Shelving Filter
A low shelving filter or low shelf filter EQ is a type of filter which cuts or boosts every frequency BELOW a certain point:
As you can see, this creates a flat/relatively constant cut or boost to whichever point you select.
For instance, setting the point at 1000Hz on a low shelving filter would allow you to cut or boost everything below 1000Hz by the number of decibels you choose.
The slope setting helps to determine how sharp or how quickly the shelf transitions, but it’s the Q setting which is instrumental in determining the shape of the shelf itself.
A moderate or lower Q setting always sounds more natural as it affects more frequencies on either side of the core point rather than making an immediate transition.
Alternatively, you can see an aggressive Q setting on a low shelving filter actually boosts one side while cutting from the other.
It’s very rare when you’ll need a Q anywhere as sharp as this on a low shelving filter because of the unnatural give and take so close to the same frequency.
Lower Q settings are generally more recommended in all kinds of EQ filters because they create more gradual slopes, leading to less phase issues and more natural sounding audio.
When to Use a Low Shelving Filter
Essentially, low shelving filters are ideal when you want to attenuate everything below a certain point without going to the degree of a full high pass filter.
I like low shelving filters when I’m trying to clean up the low end on instruments without COMPLETELY eradicating them altogether.
For instance, I’ve talked in the past about how to get the bass and guitar to work together. Oftentimes this involves using a high pass filter on the guitar as high as 300Hz or more to give that space completely the bass. The two compliment one another to form the low end of the rhythm section in many genres, but sometimes I don’t want to remove the low end of the guitar altogether.
While I would still use a high pass filter on the guitar around 100Hz to remove inaudible noise from the guitar which isn’t adding anything to the tone, I might supplement it with a low shelving filter cut in the 100-300Hz range to attenuate those lowest mids by 2-3dB.
In other words, I like using low shelving filters as a compromise between leaving a frequency I want to attenuate untouched and removing it altogether via a high pass filter.
Similar to the principle with using a more gentle Q, a low shelving filter itself can sound more natural than completely removing everything below a certain point with that high pass filter.
The next time you are planning on using a high pass filter to remove everything below a certain point, try a low shelf in its place, cutting a few dBs for a more natural and potentially better sounding solution than gutting it altogether.
Don’t forget to check out my COMPLETE and FREE EQ cheat sheet for in depth visual guides for EQing every single instrument in your mix to perfection.
