What does a low cut filter do?

If you should use a low cut filter or not depends on what source you are recording. When engaging the filter, think of it as cleaning up the signal as much as possible to get better-sounding results later in your signal chain.

For example: When you are recording an instrument that is not very bass-heavy, like a violin or a flute, it makes a lot of sense to engage the low cut on your microphone. It will not alter the sound of your instrument, but it will remove the unwanted low frequencies that can occur in every recording.

Remember, when you use a compressor later, the low end will also be boosted. So engage a low cut if your audio signal does not need the lower frequencies.

My recommendation is to experiment with a low cut on each recording and listen for yourself. If the audio sounds good with the low cut engaged, use it. The cleaner your low end on every track, the easier it will be to get a well-balanced mix later.

Sometimes, the differences between using a low cut and not using one are very subtle. But sometimes, engaging a low cut can change the flavor of a recording drastically.

Record one take with the low cut engaged and one with the low cut turned off. Listen carefully and decide if you need the lower frequencies on this particular recording.

Remember, if you use a low cut at the recording stage, you will get rid of some bass at the source. Boosting it in postproduction will not be so easy and most likely will end up sounding suboptimal. So make sure that you like what you hear when you make a decision if you use a low cut on vocals or not.

There is no general answer if you should or should not use a low cut on vocals. You have to listen and decide for yourself.

Not all low cut filters are the same. They can start their cutoff at different frequencies. Common frequencies where a low cut starts to cut off a signal are 40 Hz, 80 Hz, 120 Hz, or even 240 Hz.

Different low cuts can also have different slopes. This tells you how steep or flat the signal gets reduced.
Common settings are 12 dB per octave or 6 dB per octave. One octave is always double the frequency, for example the difference from 240 Hz to 120 Hz is one octave.

Check out this frequency graph of the LCT 1040 that demonstrates the differences in the slope. The pink line has a low cut at 80 Hz with a slope of 12 dB per octave. The blue line has a low cut at 120 Hz with a slope of 6 dB per octave.

As you can see, 12 dB per octave is steeper than 6 dB.

What settings you should use depends on your recording. Use your best judgment and listen to every recording.
There is no right or wrong answer. Only you can decide what sound you like best.

When recording vocals, the difference between 80 Hz and 120 Hz should be chosen by vocal range.

120 Hz is just low enough to capture the lowest note of the baritone range. It can work for male vocals, but it is risky. Using it for a bass singer would reduce his lowest notes in volume.
 
If it isn't absolutely clear what range the recording will be in, the safest rule is to use 80 Hz for male singers and 120 Hz for female singers who stay in a typical range.

With these settings, you will keep the crucial vocal range intact.

But before you commit to settings, it is always good to listen for yourself.

The short answer is “no”. If your microphone does not have a low cut, you can still make great-sounding recordings with it.

But a low cut on your microphone can improve your recordings and make your postproduction life easier. So, when you are looking to buy your next microphone, think about your use cases and take a decision if a low cut makes sense or not.

If you’re looking for a new microphone, check out our product finder to find the perfect microphone for you.

Low cut filters are also sometimes called high pass filters. They mean the same thing, so both terms are correct.

Low cut is more commonly used, but high pass can also be used. So, you can decide what you like better.

Microphone basics

If you want to learn even more about microphones, check out other interesting topics on the microphone basics page!