When to Use Dynamic EQ In a Mix

by Daniel Dixon, iZotope Contributor February 11, 2019

Balance your own mix:

Neutron 3

Let your vocals cut through the mix:

Nectar 3 Plus

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One of the biggest challenges when mixing with EQ is sculpting audio signals that vary in frequency content over time. A cut to tame harsh vocal frequencies works for one phrase, then comprises intelligibility the next. Rolling off lows on a drum kit might reduce masking when the bass is present in the chorus but sound thin on its own during the bridge. You can try automation to connect the dots, but it's both time-consuming and unnatural for these types of moves.

Enter dynamic EQ, which includes the three EQ parameters you’re used to—frequency, gain, and Q—with the addition of a compressor threshold, so when a specific frequency band exceeds the threshold, it triggers either a boost or cut of the EQ filter. This combination allows you to use EQ in a way that responds and adapts to incoming audio.

In this article, we’ll look at a some of the creative and corrective possibilities of dynamic EQ.

Why use a dynamic EQ?

Most EQ filters are static, meaning they boost or cut independently of audio content. While it's unlikely they will lose their place in the world of audio any time soon, dynamic EQs present an exciting new frontier for producers and engineers looking to process audio transparently—in other words, without any artifacts or perceivable changes to the listener.

While the appeal of dynamic EQ is geared toward the more techy music-makers out there, I’ve found it to be a flexible tool that can be used by anyone looking to gain a little more precision control over their audio.

Let’s look at some common applications.

Follow a vocal fundamental

Below 100 Hz, vocals carry very little important information, making it standard practice to roll off everything below this point with a high-pass filter near the fundamental. You don’t want to thin a vocal out, but you do want to remove rumble and other unnecessary noise.

Using the Follow Mode In Nectar 3 (click a node and hit “Freq”) you can introduce a high-pass filter that follows the first fundamental as it moves through the spectrum from pitch to pitch, taking the guesswork out of choosing a cutoff point.

This is helpful for all vocal performances, but particularly for those that are erratic in nature. Even if the fundamental jumps multiple octaves, the high-pass node will follow it closely so you don’t have to draw in filter automation or slice out certain phrases to new tracks for different EQ processing. 

Pinpoint vocal resonances

Some of the trickiest issues to resolve in a mix are the sporadic resonant peaks inherent to certain vocal ranges and words. Sometimes they are so pervasive you can see them poking through on an EQ graph, but they can also blend into a performance in sneakier ways.  

With a static EQ, you might start making small cuts across the spectrum to attenuate resonances as they happen in a performance. In a particularly resonant vocal, this approach can leave you with several cuts that, while solving the issue at hand, end up damaging audio quality by pulling away important vocal content when the resonances aren’t there.

A more resourceful option is to dial up that Nectar 3 Follow EQ one more time and drag nodes over the problematic areas. Introduce a small notch and they will follow the related vocal harmonics as they change throughout a performance, dulling them only when they are present.

If you are having trouble finding these frequencies, run a pass of Vocal Assistant, which creates a custom preset for your vocal based on its characteristics, and head to the first EQ module in the chain. A series of nodes will be placed at various points across the spectrum, indicating where possible issues lie.

Watch how to do both of the vocal techniques mentioned so far in the video below:

Get rid of poking frequencies

This same problem happens in all kinds of audio signals, particularly of the live variety. Not only do you have to deal with resonances caused by the instrument, but now there is room acoustics to consider. Instead of spending your afternoon hunting for frequencies, you can use the Learn feature in Neutron 3 to locate them, then hit “Dynamic Mode” to set a threshold for each node. This works the same way as the EQ in Nectar, but Neutron comes equipped with additional tools and presets better suited to instruments than vocals.

Learn how this works in Neutron below:

Get drums to “talk” to each other

Let’s imagine a snare in a drum submix is struggling to cut through because it is being masked by some of the lower frequencies of the hi-hats. If you apply a broad static EQ cut around 5–6 kHz to the entire submix you’ll end up dulling the snare sound. You can also try a cut on the hi-hat sound itself, but the masking issue only arises when the snare is present so this isn’t really helpful.

With the dynamic EQ in Neutron, you can use the snare hit as a sidechain input to the high hat track so the conflicting frequencies are only cut when the snare comes down. This is all laid out in the image below—Node 3 is positioned over snare harmonics and Node 7 is sitting on important hi-hat information. Under “Dynamic Mode” in the bottom right of the plug-in (which needs to be clicked to enable dynamic capabilities) I selected Node 3 as the internal sidechain trigger for Node 7. If I wanted to boost frequencies every time the snare landed, I would select “Up” instead of “Down.”

You can apply this same logic across an entire drum kit to carve out a precise space for each hit. If you’re working with busy drums that have too much frequency overlap or have a single drum that occurs infrequency but contains problematic resonant frequencies, this is a must-do trick.

Dulling hi-hat frequencies when the snare hits

Broad unmasking of vocals and other instruments

Beyond drums, masking issues present themselves between vocals and backgrounds, vocals and guitars, and bass and mid-range synths. The application described above applies to these instrument combinations and many others too—it may be that only certain words in the main vocal clash with the backgrounds, or that just the sustained notes in the bassline aggravate the lower parts of a synth.

Using a node or two and the sidechain trigger in the dynamic section of Neutron 3 will allow you get better control of these brief moments of collision so your mixes sound cohesive and free of distraction—without needing to make compromises with a static EQ.  

Update the classic kick-bass sidechain

Perhaps the most infamous masking example happens between the kick drum and bass track. We’ve all heard the story many times before—both instruments share a similar frequency range so that when the kick occurs at the same time as the bass, the loudest one either partially or fully obscures the other.

The common solution is to use the kick as a sidechain trigger to temporarily duck the bass every time it hits. While this works, it requires you to duck the entire bassline and not just the parts the kick interfere with, producing an obvious pumping effect that isn’t always desired.  

Dynamic EQ allows you to zero in on the specific frequency band causing the fuss between the kick and bass so you can keep the bass fundamental and other important bands untouched.

Here’s how to do it:

1. From an instance of Neutron on the bass track, activate Dynamic Mode on a node and select “Ext. Full” as a sidechain source (a kick is typically an external source from the bass submix)  

2. Create a return track and send the kick to it all full capacity. This should work in any DAW but may vary

3. Send the audio from the return track into Neutron 3

4. The kick will now trigger the bass sidechain, so you can drag the node to wherever masking occurs and it will duck frequencies according to the threshold parameter

If you need help finding exactly where masking occurs, add an instance of Relay (a utility tool that allows iZotope plugins to communicate across a session) to the kick track, pull it up in the Neutron bass EQ, and hit “Masking,” which will highlight in red where the most intense masking occurs. The red lines are where you should place nodes and experiment with gain cuts—you will find that most of the time, small cuts, as opposed to more drastic ones made without visual feedback, are often enough to tame seemily widespread masking issues.

Unmasking and dynamic EQ in Neutron


Dynamic EQ is a relatively new development in the world of audio plug-ins, and from sculpting vocals to dulling resonances, and unmasking similar-sounding instruments, it should now be clear how it can greatly improve a mix.

For those of you who were unfamiliar with dynamic EQ before this article, follow the tips listed and you will surely find new ways to employ it for both creative and corrective results.

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