What is dynamic EQ?

Dynamic EQ in plain English

A normal EQ band is set and forgotten. Cut 200 Hz by 6 dB and it stays 6 dB down for the whole song, on the quiet notes and the loud ones alike. That's what you want when a sound has the same problem all the way through, and it's how the EQ lesson teaches it.

Plenty of problems don't behave like that. An acoustic guitar can sound fine until the player digs in on the low strings, when 200 Hz suddenly booms. A singer can turn hard at 3 kHz on the loud lines only. A static cut big enough to fix the loud moments takes the body out of every quiet one too.

A dynamic EQ band listens to its own part of the spectrum and only moves when that part gets loud. Set a band at 200 Hz with a threshold just under the boomy strums, and the bell dips on those strums and flattens out again between them. The rest of the time it's a band at 0 dB, which does nothing at all.

It's a compressor that works on one slice of the frequency range and turns that slice down with an EQ bell. So it has the controls of both: frequency and Q from the EQ, and threshold, ratio, attack and release from the compressor.

How does a dynamic EQ work?

Each band has two filters set to the same frequency and Q. The first is a band-pass filter that feeds the detector. It picks out the slice of the sound the band cares about, so the detector hears only that slice and ignores everything else. The sound you hear never goes through this filter; it only tells the band when to move.

The detector compares the slice with the threshold. Once it goes over, the band works out a cut exactly as a compressor would: say the 200 Hz slice peaks 12 dB over a −18 dB threshold, with the ratio at 4:1. A 4:1 ratio lets a quarter of the overshoot through, which is 3 dB, so the cut is 9 dB. The dynamic EQ turns that figure into the gain of the second filter, an ordinary EQ bell at 200 Hz, and the bell dips 9 dB at that moment. Try those settings in the lab and the cut only gets to about 6 dB, because a 10 ms attack doesn't give the bell time to get all the way down before a short peak has passed.

Most dynamic EQs then cap the cut with a range control. With the range at −6 dB, that same strum gets a 6 dB cut and no more. When the slice drops back under the threshold, the release brings the bell back up to 0 dB.

Because the bell is the only thing touching the sound, a dynamic EQ with nothing over the threshold passes the sound through exactly as it went in. A multiband compressor can't quite say the same, since its crossover filters are always splitting the sound, even when no band is compressing. Multiband compression vs dynamic EQ runs both on the same band so you can hear the difference.

Reading the lab

The big screen shows only the slice of the loop the detector hears, with time running left to right. The pale shape is that slice going into the EQ and the teal shape is the same slice coming out, so wherever the teal is smaller than the pale, the band is cutting. The dashed line is the threshold. Underneath, the amber lane shows how far the bell has moved at each moment; hover over any point to read the numbers.

The EQ curve screen shows the band itself. The dashed amber curve is the band-pass filter that feeds the detector. The faint dashed bell is the range, the furthest the band can go, and the bright teal bell is where it is now. While the loop plays it rises and falls with the music, and when it's stopped it shows the deepest point it reached.

The panel on the right explains your settings with numbers measured on the loop. Average is the most telling of the three figures underneath, because it shows the difference from a static EQ: a band that cuts 6 dB on the loudest notes might average 0.3 dB across the loop, where a static band set to −6 dB averages −6 dB.

Band only lets you hear what the detector hears, and Static holds the bell at the full range all the time so you can compare the two. Press A/B to switch the band off. The lab matches the loudness when you do, so the only difference you hear is the change in tone. You can also upload a file or record one, and it loops through the lab in place of ours.

The controls

FabFilter Pro-Q, Tokyo Dawn Labs' free TDR Nova and Waves F6 all have dynamic EQ bands, and the names vary a little between them. The ideas are the same.

Frequency and Q

These set where the band sits and how wide it is, exactly as on a normal EQ. The detector and the bell share them, so the band listens to the same slice it cuts. A Q of 1.4 is about one octave wide, a Q of 0.7 about two, and a Q of 4 about a third of an octave. The Q and bandwidth lesson covers the maths.

Go narrower than you would on a static EQ. A static cut only has to sound right on average, but a dynamic band reacts to whatever lands in its slice, so a wide band at 200 Hz on a mix will move for the kick, the bass and the low end of the piano. Solo the band with Band only and sweep it until you hear the problem loudest.

Threshold

The threshold is the level the slice has to pass before the band moves, in dBFS. Set it just under the moments you want to fix. In the lab the 200 Hz slice of the guitar peaks at −5.2 dBFS, and a threshold of −18 dB catches the boomiest strums and leaves the rest.

Watch the Time moving figure as you lower it. A band that moves for a tenth of the loop is fixing the loud moments. One that moves for most of it has become a static cut that wobbles, which is the most common way to get dynamic EQ wrong.

Ratio

The ratio sets how far the band moves for each decibel the slice goes over the threshold. At 4:1, a slice 8 dB over gets a 6 dB cut, and at 10:1 the same slice gets a 7.2 dB cut. Some dynamic EQs, Pro-Q among them, have no ratio knob at all, only a threshold and a range.

Range

The range is the furthest the band can move. With a range of −5 dB the bell can dip as far as 5 dB and never further, however loud the slice gets. It's what stops a dynamic band from scooping a hole in the sound on the one note that was played twice as hard.

A range of 3 to 6 dB is plenty for most jobs. If you find yourself setting it past 10 dB, the problem is probably big enough to need a static cut as well.

Attack and release

Attack is how quickly the band moves once the slice crosses the threshold, and release is how quickly it goes back to 0 dB. They work as they do on a compressor, but the right values depend on how long the problem lasts.

For a boomy note, use an attack of 5 to 20 ms and a release of 100 to 200 ms, so the bell follows the note without jumping on every pluck. For esses and clicks, which last a few tens of milliseconds, use an attack under 2 ms and a release of 40 to 80 ms. Long releases hold the cut on into the notes that follow, which in the lab nearly triples the average cut on the guitar.

On low frequencies, keep the release above about 30 ms. A 55 Hz bass note takes 18 ms to complete one cycle, and a release faster than that starts following the waveform, which you'll hear as a buzz.

Cutting and boosting

Set the range above 0 dB and the band boosts when the slice gets loud. That's handy for bringing out something that only matters on the loud moments, like the snap of a snare at 5 kHz. Some dynamic EQs can also work below the threshold, so the band moves when the slice gets quiet and stays put when it's loud.

When to use a dynamic EQ

Use one when a problem in a narrow range appears on some notes or words and not others. If it's there all the time, a static EQ does the job with less to go wrong.

Boomy notes

Acoustic guitars, upright bass, piano and male vocals often have one or two notes that ring louder than the rest, because they line up with a resonance of the instrument or the room. A narrow dynamic band on that note's frequency, typically somewhere between 100 and 300 Hz, takes it down only when it's played.

Harsh vocals

Many singers get hard and edgy between about 2 and 5 kHz when they push. A dynamic band there, with a moderate Q and a 3 to 6 dB range, softens the loud words and leaves the presence in the quiet ones.

Esses

Sibilance is the textbook dynamic problem: a sharp burst between about 5 and 10 kHz that lasts a few tens of milliseconds. A narrow dynamic band with a fast attack does the job of a de-esser. The de-essing lesson goes into the dedicated tools.

Masking between two parts

When two sounds share a range, the louder one covers the quieter one, which is called masking. With an external sidechain, a dynamic band on one track can listen to another, so the bass gives up a few decibels at 60 Hz only while the kick is hitting. The next section covers it.

Mixes and masters

On a whole mix, a dynamic band can catch a range that only builds up in the loudest sections, like low mids that thicken in the chorus. Keep the range to 1 to 3 dB here, since every move affects every instrument in that range.

Using an external sidechain

By default each band listens to its own slice of the sound it's on. Most dynamic EQs, including Pro-Q and Nova, also have a sidechain input that lets a band listen to a different track instead.

The usual use is kick and bass. Put a dynamic EQ on the bass with a band at 60 Hz, a range of −4 to −6 dB and the kick on the sidechain. Each kick dips the bass at 60 Hz for a moment and leaves the rest of it alone. Sidechain compression turns the whole bass down on each kick. With the dynamic EQ only the lowest part of the bass dips, so the rest of its tone holds its level and the bass line doesn't pump.

The same trick clears room for a vocal: a band between 2 and 4 kHz on the guitar or synth bus, keyed from the lead vocal, dips while the vocal is singing and comes back up in the gaps. The lab listens only to the sound it's processing, so try this one in your DAW.

Dynamic EQ vs EQ, compression and multiband

The line between these tools is thin. A dynamic EQ band set to a low shelf behaves a lot like the bottom band of a multiband compressor, and a split-band de-esser is a dynamic EQ with fewer controls. A narrow spot that comes and goes calls for a dynamic EQ band; when a whole range needs evening out, multiband is the better fit.

How to set up a dynamic EQ band, step by step

1. Find the problem with a boostMake a narrow bell, boost it 10 dB and sweep it slowly while the part plays. Stop where the problem jumps out the most, then take the boost back to 0 dB.
2. Switch the band to dynamicSet a range of −6 dB and a ratio around 4:1. Start with a 10 ms attack and a 150 ms release, or 1 ms and 60 ms for esses.
3. Solo the bandUse the band's listen or solo button to check the detector hears the problem and not much else. Narrow the Q if other parts are getting in.
4. Lower the thresholdBring it down until the band moves on the problem moments and sits at 0 dB the rest of the time. Most plug-ins draw the moving curve, so watch it as well as listening.
5. Set the range by earMake it deep enough to fix the loud moments and no deeper. If the fixed notes sound thinner than their neighbours, ease it back.
6. Compare at the same levelBypass the band and listen. If you can't say what improved, raise the threshold or take the band out.

Starting settings for common problems

These are places to begin. The exact frequency comes from sweeping on your own sound, and the threshold depends on its level, so the table gives the usual range and leaves the threshold out.

Common dynamic EQ mistakes

A threshold so low it never lets go

If the band is moving for most of the song, you've built a static cut that wobbles, and the wobble is all it adds. Raise the threshold until the band rests at 0 dB between the problem moments, or swap it for a normal EQ band.

A band too wide for the job

A wide band hears more of the sound, so it gets set off by things you didn't mean it to. On a mix, a two-octave band at 150 Hz will duck every kick. Solo the detector and narrow the Q until it only hears the problem.

Using it for a problem that's always there

A dynamic band is harder to set up and easier to get wrong than a static one. If a vocal is muddy on every word, a static cut at 300 Hz fixes it, and a dynamic band can go on top for the few words that are worse than the rest.

Too many bands

Every dynamic band changes the tone from moment to moment. Two or three on one sound is usually the limit before the moves start to be heard as a sound of their own. If you need more, the recording or the arrangement probably needs fixing first.

Train your ears

The quiz under the lab plays the sound with no EQ, a static 10 dB cut or a dynamic band with the same 10 dB range that only cuts on the loudest moments, all at the same loudness and with the controls hidden. The static cut changes the tone from start to finish, while the dynamic band comes and goes with the playing, so listen to the quiet notes as well as the loud ones. Your best score is saved in your browser.

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