Mix Clarity: Advanced EQ and Compression Techniques

Clarity is job one when mixing, especially in modern recording. Even when your goal is a wall of sound, you still need a certain clarity, or you can easily find yourself in a muddy mess. So, we thought we’d talk about some slightly more advanced EQ and compression techniques for that purpose. We chose to put these two together because the combination of EQ and compression is a huge part of how modern mixers achieve such pristine clarity.

EQ

Let’s start by reviewing some fundamentals. So: EQ (equalization) is a fundamental audio tool that allows for precise control over the frequency content of a signal. By adjusting (aka boosting or cutting) different frequency bands, EQ can shape the tonal balance of any signal. We normally refer to five frequency bands – lows (20-200 Hz), low-mids (200-800 Hz), mids (800 Hz to 2 kHz), high-mids (2-6 kHz), and highs (6-20 kHz).

Types of EQ

EQs come in four basic flavors:

• Parametric EQ allows precise adjustment of frequency bands, bandwidth (Q), and gain. It is commonly used for surgical EQ tasks, where specific problem frequencies need to be addressed – most modern plugins are parametric EQs.
• Graphic EQ provides a set of fixed frequency bands arranged in a graphical interface, allowing simultaneous adjustment of multiple frequencies. It is useful for broader tonal shaping and overall frequency balance. Graphic EQs are usually hardware units, and they’re still common in live rigs.
• Shelving EQ controls the gain of frequencies above or below a specific frequency, creating a shelf-like curve. Low-shelf and high-shelf EQs are commonly used to boost or cut the low or high frequencies in a mix.
• Bandpass filters (either high pass or low pass) filter out frequencies below (or above) a set frequency. Most modern EQ plugins include high and low pass filter options alongside parametric and shelving options.

EQ Techniques

Now that we’ve set the stage, let’s go over some EQ techniques:

• Subtractive EQ (cutting) is all about reducing specific frequencies to create clarity. Cutting unwanted frequencies helps remove mud noise, resonance, harshness, and so on. Subtractive EQ is usually applied before other processing like compressors, and some engineers swear they only use subtractive EQ. It’s common to high-pass tracks that don’t need to contribute to the lows and to surgically remove ugliness via the “sweep and destroy” method.
• Additive EQ, on the other hand, is what it sounds like – boosting selected frequencies to enhance them. Additive EQ is common post-compressor, and it can help punch a track’s specific character through, add “air” in the high frequencies, and so on. It’s very common to see aggressive boosts on kick drums, for example, in the 5-7 kHz range – just to get them punching through on smaller speakers.
• Mid-side EQ is a more modern option, where you can adjust the frequencies and stereo image separately for the mix’s center (mid) and sides (stereo). This technique allows for precise control over the focus and width of the soundstage, enhancing clarity and separation. One great technique here is to high pass the sides at around 100 or even 200 Hz, which centers low-frequency content and tightens a mix significantly. Not all EQ plugins can do mid-side processing, though, and not all engineers bother to use it.

Dynamic EQ

Dynamic EQ is yet another advanced EQ technique but it deserves its own section, as it has so many uses, and is kind of a hybrid between EQ and compression. Briefly, dynamic EQ lets you set specific frequency bands and adjust their gain based on the input signal's level. It’s actually just a band-specific compressor. Dynamic EQ can be used in a number of ways:

• Taming Resonant Frequencies - Dynamic EQ can be used to address resonant frequencies that cause certain elements of the mix to become overly prominent or boomy. By dynamically reducing the gain of those frequencies only when they exceed a certain threshold, you can maintain clarity and balance. Great for stuff like bass, where most notes hit fine but one particular note booms and resonates.
• De-Essing and “De-Paining” - You can use Dynamic EQ to target and reduce the sibilance in vocals, and to target harsh resonance in the “pain” area (that frequency range that just hurts the ears – really common in belting tenor vocals). Set to anywhere from 4-8 kHz for de-essing, and between 2-3 kHz for “de-paining.” You can “de-pain” other elements too, like snares or guitars.
• Controlling Dynamic Elements in Instruments - Instruments with dynamic characteristics like acoustic guitars or pianos, can benefit from dynamic EQ to maintain consistency and control excessive peaks. You can do this with normal compression, but sometimes you just want to dial in a specific frequency range to tame.

Compression

Compression reduces dynamic range. Put simply, it makes loud parts of a signal quieter so that you can bring the overall level up, thus making quiet parts louder. As complex as compression can be, that’s the bottom line. Obviously, the usefulness of this tool is immense. So, let’s look at some specific techniques here.

• “Transparent” compression means applying gentle compression to control dynamic peaks and create a more consistent sound without altering the overall character. By using a low ratio (e.g., 2:1 or 3:1) and longer attack and release times, transparent compression can smooth out transient peaks and bring out subtle details in the mix. Subtle compression like this is great for the mix buss and basically any element you don’t want to really alter.
• Serial compression is the art of using one, two, or even three subtle compressors in series as a way to achieve loudness and/or presence without making a signal sound squashed (as it would if you achieved the same loudness goal with one compressor). This is super common in mastering when you want to get the mix loud without compromising it. It’s also an important concept to keep in mind over the whole course of a mix – and something to keep track of. Elements may be compressed a number of times over the course of the project. For example, a backing vocal might have a smidge of compression during tracking, another bit during mix, another little bit on the backup vocal buss, and finally get compressed again as part of the final mix buss. In a dense mix, letting elements get this subtle treatment at multiple stages can really make things clearer – but you want to keep track. Some elements may not benefit from too many layers of compression.
• Multiband compression allows for independent compression of different frequency bands. By dividing the audio spectrum into specific ranges, each band can be compressed separately, addressing any frequency-specific dynamics issues. Multiband compression is particularly useful for instruments with varying tonal characteristics across the frequency spectrum. It’s common to see it in mastering to tighten up the low end. Don’t confuse this with dynamic EQ – the two are similar but not quite the same thing.
• Sidechain compression uses the signal from one source to trigger compression on another. This technique can create space in the mix by reducing the volume of certain elements whenever a specific sound, such as a kick drum, is present. Great for subtly making room for the kick by sidechaining the bass to it. Sidechain compression is also common in genres like EDM to create that tell-tale pumping effect.
• Parallel compression involves mixing a heavily compressed signal with an uncompressed signal. This technique lets you really squash a source while retaining the natural transients and punch of the original sound. It can add depth, impact, and overall loudness to individual tracks or the entire mix. Most commonly used for drum busses and in mastering.

The artful interplay of compression and EQ, and using them in tandem, is a large part of how the best mixes are so clear and audible, while still maintaining a kind of unity. This concept is huge for mixers, and once you start to master using your EQs’ and compressors’ full capabilities in tandem, you start to see palpable improvements in your mixes. Hopefully, this has helped you in that endeavor!

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