I often read or hear from colleagues or musicians that you should always use a low-cut filter when mixing a song in every channel in order to clean up. Of course I never think of such truths! Especially not in audio engineering. But is that really true and what is the best way to use such a filter?
To go deeper into the subject, I would like to briefly examine what a low-cut filter actually is and where you can find it. Basically, this filter processes the bass range by lowering deeper signal components and thus helps to clear it up. Often it is only switchable and has a fixed, so-called cutoff frequency. You are probably familiar with it from microphones or mixing consoles as a so-called "impact sound filter", which, as the name suggests, removes impact noise, or with a variable frequency in plug-ins as a "high-pass filter" that allows high signal components to pass!
Basically, the low-cut filter always works with two possible parameters. On the one hand, this is the so-called cut-off or corner frequency, from which the filter works, and on the other hand, the slope of the filter, which describes the strength of the attenuation.
The cutoff frequency, specified in Hz, is defined as the frequency above which the signal amplitude is attenuated by -3dB. The slope, specified in dB / octave, defines which attenuation value is already present at half the cutoff frequency. Here is a small example: If a low-cut filter has a slope of 6 dB / oct. at 80 Hz, this means that it was already attenuated by 6 dB at 40 Hz. You call this a first-order filter. When specifying 12dB / oct. you speak of a 2nd order filter, with attenuation 18 dB / oct. of 3rd order etc. The whole thing is justified in terms of circuitry in electrical engineering, but would go too far here.
It is only important that the higher the slope, the higher the artifacts, which are noticeable in phase shifts and also clear changes in the sound outside the filter working range. This is why you will usually not find filters above 12 dB / oct. in analog devices! The situation is different with plug-ins, here there are also very effective slopes of up to 48 dB / oct. However, the developers also use alternative filter curves for the respective area of application in phase-linear modes to reduce the artifacts.
Low-cut filters can be found in the studio at all corners and ends! Above all in the analog world, it is often implemented as a switchable filter in microphones, preamplifiers, channel strips or mixing consoles. And also often as an additional filter for equalizers or compressor plug-ins in the DAW.
As in the “Technical” section above, the digital version is far superior to the analog version. Especially when it comes to phase accuracy and the retention of the sound.
If you want to thin out musically, you have to be careful not to do too much, but only to deliberately consider using lo-cut filters.
Because your individual sounds must actually be able to connect to a new whole. And this also includes the low frequency components of your signals determining the overall sound.
Prefer to work with shelf or bell filters or dynamic equalizers.
If you simply use lo-cut filters everywhere in the mix on all of your individual tracks, maybe even with a high order, then the filters may influence each other and your mix will not be more transparent, but rather non-transparent. Phase problems give your mix strange artifacts and suddenly appear lifeless.
Between all the tools that you can use in the studio to achieve your desired goal, the low-cut filter is an effective and at the same time simple tool.
It can clean up your production and intervene clearly in terms of sound.
It is important to me that you know that there is not just one given way to use a filter for recordings or mixes. Hear and decide which signal benefits or can be better worked out by using a filter.
Of course, this also requires good listening conditions and, above all, that you know where you want to go with your production.
But basically let each instrument have its roots, because this is the only way your mix will arouse emotions in the listener and not appear sterile!
Tell me about your experiences with lo-cut filters in the comments.