How and When to Use Dynamic EQ

May 24, 2017

Learn what dynamic equalizers do, how they work, which problems they can solve, and how they’re different from both regular EQs and multiband compressors.

You’ve got a problem: Sometimes, when you go outside, you get wet.

You identify the cause: Rain, falling from the sky.

You devise a solution: Use an umbrella. Not all the time, of course – there’s no need when the weather is clear, and besides, you enjoy the warm sun on your face, the breeze blowing through your hair. And even on the days when it is raining, you might not open the umbrella when it’s just drizzling, or if you do, you might only use it for brief periods of time.

You’re mixing, and you’ve got a problem: The kick drum isn’t coming through with enough punch.

You identify the cause: There are similar frequencies in the bass which are masking the snap of the kick drum beater.

You devise a solution: After trying standard compression on the kick drum track (which just makes things worse) and on the bass (which does nothing to help the kick), you turn to equalization. That doesn’t work either, since cutting a notch in the bass to allow the snap of the kick drum to come through more clearly affects the sound of the bass all the time, not just when the kick is heard.

But then you plug in a dynamic equalizer. Problem solved! Cut that same notch in the bass sound, but use the kick drum signal as a sidechain trigger and set extremely fast attack and release times so that the frequency content of the bass is altered only during the split second that the kick drum is played. With the masking frequencies of the bass momentarily reduced through compression, listeners are better able to hear the kick drum.

For this kind of application – and so many others – dynamic equalization provides a better solution than traditional, ‘static’ EQ. Whereas regular EQ is applied to the sound from start to finish, dynamic EQ combines precision equalization with selective compression/expansion and sidechain triggers, kicking in only when the signal you’re EQing goes above a certain threshold at the frequency you’ve selected.

Why ‘Static’ EQ May Not Be Enough

Just as you don’t need that umbrella all the time, you don’t need equalization all the time. After all, music, like the weather, changes. Songs consist of multiple sections, each eliciting different moods and emotions. Some sections are loud, others are soft. Some notes are played legato, others staccato. The drummer pulls and pushes the beat. Instrumentation may vary, as well as the registers the instruments play in, which in turn affects their timbre. The singer attacks the choruses differently from the verses, emphasizing certain words (or even certain syllables), backing off on others. And even the most perfectly set-up instruments, played by the most skilled musicians, tend to produce certain notes louder than others (a common problem with bass in particular).

So the reason why traditional equalization alone is sometimes not enough comes down to this: One size does not fit all. Apply ‘regular’ EQ during mastering, and boosting some upper midrange (say, around 3.5 kHz) will add bite to the guitar but will also make the vocal shrill whenever it strays into that area. Apply some low frequency shelving at 60 Hz, and it will reduce the boom of the kick drum – but it will also affect the fundamental of the bass when low notes are played. Applying EQ to individual instruments during recording or mixing does not solve the problem, either. A good setting for a vocalist singing softly rarely works when they begin attacking the chorus at a louder volume. Rolling off high frequencies to reduce the harshness of cymbal crashes will dull their sound even when they are tapped gently.

F6 Floating-Band Dynamic EQ

When to Use Dynamic EQ

In essence, a dynamic equalizer allows you to EQ the louder parts of a track (or, more precisely, the louder parts of a particular frequency in the track) differently than the quieter layer just under it. Here are some common use cases:

You can rein in the shrillness in a singer’s voice when he or she begins belting out the chorus, while still retaining vital presence during the quieter verses.
Let’s say a hi-hat is too bright in a mix, but you’re happy with the snare sound. If you try and compress (or apply traditional equalization to) the hats, you’ll end up also dulling the snare sound. With a dynamic equalizer, you can use the snare hits as a sidechain input to the high-hat track so that you only roll off top end whenever the snare isn’t being hit. You can even EQ the transient of a sound one way, and the sustain portion a different way – scoop out the “boxiness” of a sound without affecting its attack at all.
You can tame harsh cymbal crashes when the drummer starts getting carried away, but leave the cymbals untouched when the drummer is playing with a bit more restraint.
You can control bass guitar nodes only at certain times and not statically throughout the whole song.
You can reduce or eliminate snare or tom resonance problems, as well as that annoying boominess that sometimes occurs when certain notes are played on acoustic guitar – especially important when the problem frequencies sit close to those of other instruments in the arrangement.

Here’s a more detailed example of how you can use a dynamic EQ:

Let’s say that the instruments and the lead vocal are competing with each other for the same space in a mix. If your dynamic EQ has a mid-sides processing option, you can use it to carve out a spot for the lead vocal without affecting the rest of your mix. For example, here’s how you can do it with the F6 Floating-Band Dynamic EQ:

Group the instruments to a stereo buss.
Insert the F6 stereo component on this buss.
Route the lead local to the F6 Dynamic EQ as an external sidechain.
In this example, we’ll use Band 4 for processing as follows:
(a) Switch the mode to MID
(b) Switch SC SOURCE (sidechain source) to EXT (external)
(c) Set Frequency to 1600 Hz
(d) Widen the Q to 0.6
(e) Set Range to -2.5 dB
Now play your audio (the instruments and the lead vocal together). The lead vocal’s input level is indicated on the Threshold SC meter. The positon indicator on the Threshold knob indicates whether Band 4’s Threshold is above or below the lead vocal’s input level.
Slowly lower the Threshold level. When Threshold falls below the level of the lead singer, Band 4’s compressor will begin to attenuate only the mid channel. From there you can continue to tweak to your liking.

Learn more about mid-side dynamic equalization in this video with mix engineer Brad Divens (Kanye West):

The Difference between Dynamic EQ and Multiband Compression

Dynamic equalizers and multiband compressors are similar in certain key respects: both compress and expand selectively; both process your audio in a way that link the dynamics of a track with its frequency spectrum.

But whereas multiband compressors use crossover filters, which affect fairly broad frequency areas, a dynamic EQ allows you to specify the precise frequencies you want to boost (through expansion) or attenuate (through compression). The F6 Floating-Band Dynamic EQ offers six such “floating,” or fully adjustable bands, each with full control over width (“Q”), gain, range, threshold, attack, and release. What’s more, internal and external sidechain inputs are provided for each band so that the specified frequency is compressed or expanded only when the sidechain signal exceeds a user-defined threshold. In addition, a unique “split/wide” mode allows you to optionally filter the audio being used as the sidechain trigger.

All these features make dynamic equalization a powerful and extremely flexible tool that can be applied during mixing or mastering, as well as in live performance. By letting you surgically zero in on trouble spots and then treat them only when trouble arises, a dynamic EQ can serve as the ultimate problem solver.

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