How To Use A Low Pass Filter

Only about every mixing tutorial on the interwebs sings the praises of the highpass filter — indeed, information technology's a useful tool. Inexperienced hands, highpass filters tin can shape your low stop, add together clarity to your tracks, eliminate depression-frequency mud, and restore precious headroom.

The highpass filter's unassuming cousin — the humble lowpass filter — doesn't seem to get the same corporeality of respect.

Admittedly, a lowpass filter won't produce as dramatic a result as a highpass filter. That said, well-placed lowpass filters can tame unruly hiss and sibilance, while calculation polish and dimensionality to your mixes.

In this blog, we'll discuss what a lowpass filter is, and we'll outline several common means that you can implement this essential tool in your own mixes.

What is a Lowpass Filter?

A lowpass filter removes frequencies above a defined cutoff frequency, while assuasive those below to pass. This enables yous to benumb (lower the level of) high frequencies.

Most commonly used parametric equalizer plug-ins — FabFilter Pro-Q, iZotope Neutron, Waves Q10, and even the ane that comes arranged with your DAW — include this blazon of filter, besides as highpass, bell, shelf, notch, and other shapes.

The plethora of different EQ plug-ins out there each contain a unique command set. The two near common controls that you lot will encounter on a lowpass filter are:

Frequency defines the cutoff frequency of your filter, meaning that all frequencies above it will exist adulterate. This is indicated in hertz (Hz or kHz).

Higher frequency settings will yield less aggressive filtering. For example, a 15kHz cutoff frequency will attenuate fewer frequencies than a 5kHz cutoff.

Slope determines the steepness or severity of your filter. This is measured in dB-per-octave increments.

The college the slope is prepare, the more ambitious the filter will attenuate high-frequency sounds. For case, a filter with a 6dB-per-octave slope would offer a more subtle effect than a filter with a 24dB-per-octave gradient.

Common Uses for Lowpass Filters

Eliminate Unwanted Elements

Listen to your mix. Do you hear any undesirable or excessive high frequencies? If that's the case, a lowpass filter may be the perfect solution

Eliminating a track'due south loftier-frequency content tin actually do good your mixes, specially if the offending frequencies aren't adding annihilation compelling.

Say you have a kick drum with a piercing "click" audio or a bass guitar that's drenched in fuzz or distortion. These are both depression-frequency instruments — their high-frequency content is oftentimes not essential.

Whenever yous increase the level of these tracks, their high-frequency content will become louder besides. This tin have the side outcome of burying other instruments that comprise lots of high frequencies within your mix.

Deploying a lowpass filer in the 10kHz–15kHz range is an easy and effective way to tame out-of-control high frequencies, while simultaneously bringing out a track'south lower frequencies. But be gentle — filter too aggressively and your track volition turn into mud.

Solve Frequency Collisions

Mixing is all about carving out sonic space. But like you'd use a highpass filter to create space for low-frequency instruments, you tin can utilise a lowpass filter to brand room for loftier-frequency instruments.

A common rookie mistake that novice engineers make is to add together desirable frequencies instead of removing undesirable ones. If your lead vocal track is being masked by layers of synthesizers or walls of high-gain guitars, resist the urge to crank the vocals — instantiate a lowpass filter on the competing track instead.

Again, at that place's no reason to exist heavy-handed with this. Apply just enough filtering to unveil the buried track. Too much filtering, and your track volition lose its definition and clarity.

Not sure which frequencies are the problem frequencies? No trouble. Our MIXROOM plug-in will guide you through the process every stride of the way, supplying you with what yous need to improve your sound and attain a pro-sounding mix.

Uncover Lead Vocals

One of the nearly infuriating frequency collisions you'll meet while mixing is between pb and background vocals. And the more vocal tracks you add, the more pronounced the problem becomes.

It's all about competition. Later on all, there's only and then much frequency bandwidth to become around. And considering they all contain similar-sounding material, your song tracks are going to clash with — and mask — i another.

To resolve this, identify a lowpass filter on your groundwork vocal tracks with a cutoff effectually 5kHz–12kHz. This will decrease the number of conflicting frequencies between the tracks, enabling your lead vocals to sit down at the forefront of your mix.

Better Dimensionality

While mixing, we tend to focus on the stereo field — panning from left to right. That said, front to back is equally as of import.

After all, this is how we perceive space in the real earth. If something is close to u.s., it'due south loud and bright. If it'southward farther abroad, it's quieter and less bright.

In a mix, nosotros tin can re-create this sort of dimensionality by lowering a runway'southward volume and rolling off some of its high end.

Go on your mix'south focal points, such as vocals, drums, guitars, and solo instruments, up front end. Gently push pads, auxiliary percussion, and other decorative elements back — just don't push them back as well far.

Maximize Reverb Effects

If an inexperienced mix engineer applies also much reverb to a vocal, information technology obscures the track's transients, reducing the performance to an inarticulate mess. On the other manus, a pro-level mix engineer can drown a vocal in reverb, while maintaining every ounce of the rails's clarity and intelligibility.

E'er wonder how they do information technology? One technique is to use a lowpass filter set around 10kHz–12kHz to just the reverb event.

Similar we discussed earlier, rolling off a rail'due south top terminate pushes it dorsum into the mix. The aforementioned applies to reverb. Rolling off its upper frequencies tucks information technology out of the way, leaving room for your vocal to polish — fifty-fifty in the midst of long, lush ambient.

Add Bite and Clarity

Lowpass filters can also be used to add edge to an anemic-sounding track. Instead of cranking the rails's upper midrange frequencies for actress bite, use a resonant lowpass filter instead.

What's a resonant lowpass filter, you might inquire? In a nutshell, information technology creates a boost at your specified cutoff frequency prior to attenuating it.

If you place a resonant lowpass filter at merely the right frequency in your flat-sounding track'due south upper midrange, it will inject it with bite, clarity, and free energy, while gently attenuating all of the competing frequencies above it.

There'due south no reason to do anything desperate — push this technique too far and you'll end up with a harsh, indigestible-sounding track.

Eradicate Distracting Hiss

Always been handed a mix with a rails that contains a steady stream of high-frequency hiss? If you haven't, you lot will — it happens to everybody sooner or later.

While at that place are a lot of advanced dissonance-reduction tools out in that location, they tin be overkill in some situations. In the case of high-frequency hiss, deploying a lowpass filter set effectually 8kHz might do the fox with a lot less try than deploying a more circuitous solution.

Just adjust the gradient until you attain a natural-sounding result. You definitely don't want to get carried away with this technique — hyper-aggressive lowpass filtering will yield a dull, muffled character that may be more objectionable than the hiss.

Conclusion

While they're not a tool that you lot'll want to use aggressively on every runway in your mix, lowpass filters are an of import part of every seasoned mix engineer's arsenal. These indispensable sound shapers give you a lot of creative and cosmetic control over your mix and are an like shooting fish in a barrel-to-use problem solver in a myriad of situations.

We want to remind yous again, however — be gentle ! Ham-fisted utilize of lowpass filters — and equalization in full general — can create more problems than information technology solves.

Nonetheless, learning to deploy lowpass filters properly volition drag your mixes, imbuing them with depth, residual, and clarity.

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