Work smarter with high and low pass filters

By | April 4, 2021


High- and low-pass filters, or low-cut / high-cut as they are also called, have the task of cutting off frequencies below or above a certain frequency with the help of an equalizer. This is to filter out unwanted energy that can otherwise cause problems when you mix. You may not hear it, but it’s there. And the more channels you work with, the more important it is to keep extra track.

Simply put, there are:

  • Those who use high- and low-pass filters routinely, without thinking much.

  • Those who listen, analyze and consider each channel carefully.

I myself end up somewhere in between. Partly for reasons of convenience and partly because at this point I consider myself to have such good control that I can treat myself to go on feeling sometimes.

Many have learned to work with high-pass filters on all channels, which is generally a good idea because a lot of energy collects at the bottom. Nevertheless (but much less frequently used), the low-pass filter, whose task is to remove noise and other hissing, is below the selected frequency.

1340491612_hogpass.thumb.png.9842a3f1ad7f114aa2af6de4b6d2173b.pngLow-pass filter (low-cut) at 100 Hz, whose task is to remove unwanted energy in the bottom region, but also higher up if the need arises.

907999656_lagpass.thumb.png.b26169586501c2eaa70010aa6a55f700.pngLow-pass filter (high-cut) at 8000 Hz, whose task is to filter out high-frequency noise of various kinds, sometimes audible, sometimes not.

When it comes to filtering out frequencies, there is a common belief that you should listen to the solo, preferably in headphones, to hear exactly what you are picking away. You steer until you hear the sound change, that is, the bass starts to disappear if you use a low-cut filter, or the treble suffers if you use a high-cut filter. To then go back a little. It is perfectly ok to work like this, because then you do not risk changing the basic sound but only removing the excess energy.

Another way to hear

My thinking, however, is different, as I have recently gone from being relatively restrictive with my filtering to being much more bold. For me, it’s about the context and nothing else. Let me develop.

Virtually each mix has one or more elements that are directly dependent on bass frequencies. May it be a bass keg, bass or something else that requires a lot of bottom. I let these instruments act as guides for other channels. Instead of listening solo to the instruments that are to be high-pitched, I do it at the same time as I listen to, for example, the bass. In this way, I automatically filter more aggressively, because the base (which is played at the same time) now takes care of and fills in the information I gradually remove.

In practice, this can mean that I set a high-pass filter at 200 Hz, instead of maybe 100 Hz if I had listened solo. Lots of much-needed energy can be saved here. What does this do for you, you may be wondering? Quite a lot, especially if you work with many channels. Because as we all know, it is the whole that counts and not how an instrument sounds alone (if it does not play alone). The content: Filter in the context and you get a clearer bottom and a better defined mix with maintained sound quality.

Nevertheless, each mix has one or more instruments that feel good with a little extra air and those that can do without. Here I work in the same way as with the base frequencies, but vice versa. Usually I leave lead vocals, acoustic guitars and possibly the overhangs of the drums untouched. It is also these who may act as signposts for other instruments.

With that said, I advise you not to bother with it unnecessarily, listen and steer. Do not overthink. There is, in my opinion, no reason to be too zealous about high- and low-pass filters. Do what feels right and do not get caught up in the details.

Feel free to ask questions or comment on the article in the comment field below, and we will spin the topic together. Or if you prefer to discuss mixing in the “Mixing and mastering” section of the Studios forum here!

Fredagstipset is a recurring series where Studio writer Jon Rinneby shares tips every Friday in, among other things, recording and mixing. Here you will find all Friday tips.