EQ is the foundation of every great mix. Here's how equalisation actually works, when to cut vs boost, and the frequency ranges that shape your sound.
TL;DR
EQ shapes the tonal balance of individual sounds and the overall mix. The golden rule: cut to fix problems, boost to enhance character. Learn the key frequency ranges (sub-bass, bass, low-mids, mids, presence, air) and what each contributes to your mix. Subtractive EQ almost always sounds better than additive.
What EQ Does and Why It Matters
Equalisation is the process of adjusting the volume of specific frequency ranges within an audio signal. Every sound occupies a range of frequencies — from the deep sub-bass rumble of a kick drum to the airy sparkle of a cymbal. EQ lets you shape these frequencies to make sounds clearer, fuller, brighter, warmer, or more present.
In a mix, EQ serves two primary functions: corrective and creative. Corrective EQ fixes problems — removing mud, reducing harshness, eliminating resonances. Creative EQ enhances character — adding warmth, presence, airiness, or bite to sounds that need it.
EQ is the most-used tool in mixing because every sound in your mix occupies frequency space, and when multiple sounds occupy the same frequencies, they mask each other. A bass guitar and a kick drum both produce energy around 60-100Hz. Without EQ to carve space for each, they'll fight for attention and the low end will sound muddy and undefined.
The Frequency Spectrum: A Producer's Map
Sub-bass (20-60Hz): the felt-rather-than-heard rumble. Adds physical weight to kicks and bass. Too much here and your mix sounds boomy on big speakers; too little and it feels lightweight. Most speakers below studio monitor size can't reproduce these frequencies accurately, which is why they're easy to get wrong.
Bass (60-250Hz): the body and warmth region. Kick drums, bass guitars, and the lower end of vocals and guitars live here. This range gives music its warmth and fullness, but excess energy here is the most common cause of muddy mixes.
Low-mids (250-500Hz): the 'boxy' zone. Too much energy here makes things sound like they're in a cardboard box. Gentle cuts in this range clean up mixes dramatically. It's also where the body of snare drums and male vocals lives, so cutting too aggressively makes things thin.
Mids (500Hz-2kHz): the clarity range. This is where the fundamental frequencies of most instruments and vocals compete for attention. Good mixing is largely about managing this range — ensuring each instrument has its own space rather than everything piling up in the same midrange frequencies.
Presence and Air: The Top End
Presence (2-5kHz): where vocals cut through a mix, where guitar bite lives, where snare crack happens. Boosting here makes sounds more forward and intelligible. But this is also the harshness zone — too much here is fatiguing and unpleasant to listen to.
Brilliance (5-10kHz): sibilance in vocals, the 'sizzle' of cymbals, the detail and definition of acoustic instruments. This range adds clarity and articulation but can become painful if overemphasised.
Air (10-20kHz): the sense of openness and space. A gentle boost here adds a 'finished,' polished quality to mixes. It's subtle but perceptible — like opening a window in a stuffy room. Too much sounds harsh and brittle; just enough sounds like magic.
The key insight: every frequency range has a character, and understanding those characters lets you make intentional decisions about how your sounds and your mix should feel. EQ isn't just a technical tool — it's an expressive one.
Practical EQ Techniques
High-pass filtering is the single most useful EQ technique. Apply a high-pass filter to every track that doesn't need sub-bass energy — vocals, guitars, pianos, synth pads, snares. Cutting everything below 80-120Hz on these tracks removes low-frequency rumble and mud that clutters the mix, making space for the kick and bass to breathe.
The 'sweep and destroy' technique: set a narrow EQ boost of 6-10dB, then slowly sweep it across the frequency spectrum while listening. When you hit a frequency that sounds particularly bad — boomy, nasal, harsh, or resonant — cut that frequency by 3-6dB. This technique is excellent for finding and removing problem frequencies.
Subtractive EQ (cutting frequencies you don't want) almost always sounds more natural than additive EQ (boosting frequencies you do want). If you want more brightness, try cutting the low-mids rather than boosting the highs. If you want more punch, try cutting the muddiness rather than boosting the attack. The result is often the same perception with a more natural sound.
Reference your EQ decisions. Make changes, then bypass the EQ and compare. Does the equalised version actually sound better, or have you just made it louder (which always sounds 'better' to our ears)? Match volumes before comparing and trust your ears over your eyes.
EQ in Context: Mixing for the Whole, Not the Part
The biggest EQ mistake beginners make is EQing sounds in solo. A vocal that sounds warm and full when soloed might sound muddy in the context of the full mix. Always make EQ decisions while listening to the full mix, not individual tracks in isolation.
Think of EQ as carving space for each instrument. If the vocal needs to be heard clearly, consider cutting the 2-4kHz range on competing elements (guitars, synths) rather than boosting it on the vocal. Creating space through subtraction is more effective and preserves the mix's overall balance.
The 'everything loud' trap: if every track is individually EQed to sound full and bright, the mix will be a wall of competing frequencies with no clarity. Great mixes have sounds that are individually imperfect but collectively balanced — the bass is warm but not bright, the vocals are bright but not too full, the guitars are edgy but not boomy. Each element sacrifices something for the benefit of the whole.
Trust the process and trust your ears. EQ is a skill that develops over thousands of hours of practice. The more you mix, the more your ears learn to identify frequencies, diagnose problems, and make effective corrections. Every mix session makes you better, so keep mixing and keep learning.