August 6, 2025 · Ilmari Koskinen

EQ problem frequencies: an interactive map of what to cut and why

Most EQ moves are cutting a handful of problem frequencies. Click through an interactive 20 Hz–20 kHz map to hear what mud, boom, honk and sibilance are, and how to fix each one.

Most of EQ is cutting a small set of problem frequencies that show up in almost every mix. Sub-30 Hz rumble, low-mid mud around 250 Hz, a boxy 450 Hz, harshness at 3.3 kHz, sibilance at 7 kHz: learn the usual suspects and where they live, and mixing turns from guesswork into a short checklist. You boost to add character now and then, but you spend most of your time subtracting the ugly stuff.

Below is an interactive map of the audible range, 20 Hz to 20 kHz, drawn on a log scale the way your ears actually hear pitch. Every pin marks a spot that commonly needs attention. Click one to see what it sounds like, why it happens, and how to fix it.

Subsonic rumble25 Hz · Sub

energy you can't hear but pay for

Sounds like: Below about 30 Hz your speakers move air your ears barely register. It steals headroom and makes the low end flabby without adding anything you can hear.
Cause: Mic-stand vibration, foot taps, HVAC hum, room resonance and DC offset all pile up down here.
Fix: High-pass every track around 30 Hz. Even the kick and 808 usually lose nothing above their fundamental, so trim below 30 to tighten the bottom. Push the filter up until the low end thins, then back off a touch.

Low-end masking50 Hz · Sub

kick and 808 fighting for the sub

Sounds like: The kick's weight and the bass's fundamental both sit here, and when they stack on the same note they mask each other into one indistinct thud.
Cause: Kick and 808 sharing the same fundamental and playing at the same time, so neither reads clearly.
Fix: Decide who owns the sub. Sidechain the bass to the kick, or carve a narrow dip in the bass where the kick's fundamental sits. Keeping both on the same note but an octave apart helps them lock instead of clash.

Chest punch80 Hz · Low

the thump you feel, not hear

Sounds like: Around 80 Hz is the punch you feel in your chest and the warmth under bass and toms.
Cause: Too little and the low end feels weak on big systems. Too much and it booms and buries the beater click of the kick.
Fix: Boost gently for weight, cut if the bottom feels one-note. On a kick, pair a small lift here with a bump at 3–5 kHz for the beater, so it still reads on small speakers.

The boom134 Hz · Low

the resonance nobody misses

Sounds like: A boomy, one-note resonance that piles up near 130 Hz on acoustic and electric guitars, vocals and bass.
Cause: Body resonance of the instrument and room modes converging in one narrow band.
Fix: A small, narrow cut around 134 Hz on a few key tracks cleans up the whole low end. It's a surgical dip, not a wide scoop, so don't overdo it.

Pitch smear220 Hz · Low mids

where processing shifts your notes

Sounds like: In the low mids, semitones sit only a few Hz apart. At A3 (220 Hz) the next semitone is about 13 Hz away, so any wobble can smear one note into sounding like its neighbor.
Cause: Heavy saturation, clipping or modulation (chorus, modulated reverb and delay) reshapes the waveform enough to double a peak or trough and shift the perceived pitch.
Fix: Go easy with saturation and compression on low-mid parts, and watch modulated effects here. If a bassline turns harmonically blurry after processing, pull the drive back before you reach for EQ.

The mud250 Hz · Low mids

swampy low-mid buildup

Sounds like: The swampy muck that shows up when every track carries some low-mid energy and it all stacks into a blanket over the mix. Most common on guitars and bass.
Cause: Low-mid content from dozens of layers adding up. Each part is fine alone; together they clog.
Fix: Cut a few dB somewhere between 200 and 400 Hz on the offenders. This range is also warmth and body, and 300 Hz is the lowest note many phone and laptop speakers reproduce, so thin it, don't scoop it hollow.

Boxiness450 Hz · Low mids

cardboard and hollow tone

Sounds like: A hollow, cardboard-box tone that makes drums and vocals sound like they were tracked in a small closet.
Cause: Room reflections and cheap-mic coloration bunching up in the 400–600 Hz range.
Fix: Sweep a narrow boost through 400–600 Hz to find the worst spot, then cut a few dB there. Snares and toms especially open up once the box is gone.

Honk900 Hz · Mids

talking through your nose

Sounds like: A nasal, honky quality that makes vocals and guitars sound pinched, like someone talking through their nose.
Cause: Buildup around 800 Hz to 1 kHz, often from the source itself or a midrange-heavy amp tone.
Fix: A narrow cut near 900 Hz clears the honk. Sweep to find the exact note that sticks out, since it moves with the source.

Vocal information1.5 kHz · Mids

where the words live

Sounds like: This is where the meaning of a vocal sits. Formants, the frequency clusters that spell out each vowel, cluster through the mids, and a voice's first two land right around here.
Cause: Almost every instrument has overtones through the mids, so the vocal's formants fight guitars, synths and the top of the bass for the same space.
Fix: Carve room for the vocal here instead of turning it up. A gentle dip around 1–2 kHz on the busiest backing parts lets the voice sit forward on its own.

Clarity (F3)3 kHz · High mids

intelligibility and presence

Sounds like: Between 2 and 5 kHz is where we hear clarity, because the ear canal resonates right in this range. The third vocal formant lives here, and it decides whether you can make out what someone is singing.
Cause: Human hearing is most sensitive through here, so it is the first place a mix reads as clear or as muffled.
Fix: If a vocal or lead sounds unclear, boost gently between 2 and 5 kHz. If it sounds too upfront or harsh, cut there instead. Isolate the exact spot and very little movement changes a lot.

Piercing peak3.3 kHz · High mids

the frequency your ears hate

Sounds like: 3.3 kHz is where human hearing peaks in sensitivity. It is the pitch of smoke alarms, sirens and doorbells for exactly that reason, and too much of it sends listeners reaching for the volume.
Cause: Cymbals, distorted guitars, bright synths and pushed vocals all crowd this most-sensitive band.
Fix: You need some of it for presence, so do not gut it. Tame the peaks with a narrow cut or a dynamic EQ that only pulls down when it spikes, rather than a permanent scoop.

Presence and bite5 kHz · High mids

attack and definition

Sounds like: The attack and edge of a sound: the click of a kick, the crack of a snare, the bite that makes a vocal cut through.
Cause: Missing here, sounds feel dull and buried. Overcooked, everything turns aggressive and tiring.
Fix: A small boost around 4–6 kHz adds bite and pushes a part forward. If the mix feels dull, look here before you reach for the very top.

Sibilance7 kHz · Highs

ice picks on the S sounds

Sounds like: Screechy sibilance and the scrape of finger-picked strings. On vocals it is the harsh "ess" and "tss" that feel like ice picks in your ears.
Cause: Consonant and pick energy concentrating between 6 and 8 kHz, made worse by bright mics and compression.
Fix: De-ess it: a dynamic cut around 6–8 kHz that clamps down only when the S hits, so you keep brightness everywhere else. This range is paramount to a hi-fi voice, so catch the spikes, do not kill it.

Fizz10 kHz · Highs

brittle, papery top

Sounds like: A thin, fizzy edge that makes distorted guitars and cheap cymbals sound brittle and papery.
Cause: Digital distortion, over-bright samples and aggressive high-shelf boosts pushing thin energy up top.
Fix: A gentle high-shelf cut above 10 kHz smooths it out. If only one part fizzes, fix that part rather than dulling the whole master.

Air14 kHz · Air

openness and sheen

Sounds like: The air band is the open, expensive sheen at the very top, the sense of space around vocals and cymbals.
Cause: Missing air makes a mix sound closed and dull, which is why this is the friendliest end of the spectrum: the move is a boost, not a cut.
Fix: A wide, gentle high-shelf boost above 12 kHz adds air and polish. Keep it subtle, and use a clean, low-noise EQ so you do not lift hiss with it.

Notice how the pins bunch up in the middle. That’s not an accident, and it’s the first thing worth understanding.

Why are the mids the most important range?

The mids carry the most information in a mix, even though the subs and lows hold more raw energy. Almost every instrument has overtones through the midrange, so it’s the busiest, most crowded part of the spectrum, and the part that decides whether a mix sounds clear or congested.

The reason is in the harmonics. Every instrument produces a fundamental (its lowest musical note) plus a stack of harmonics above it. Think of a kick as a low-frequency instrument, sure, but only its fundamental and maybe one harmonic sit in the lows. The click, the body, and most of its overtones are up in the mids. A bass guitar has a low fundamental, and yet the tone and character you recognize come from midrange overtones. A vocal’s fundamental might hover in the low mids, but the sound of the words lives higher up. Not everything reaches the sub or the air. Almost everything passes through the mids.

Two things make the midrange do more work than its energy suggests:

Vocal formants. The vowels you hear are clusters of frequencies called formants, and the main three all sit in the mids. The highest and most important one lands between 2 and 5 kHz, right where your ear canal resonates and hearing is sharpest. That’s why this band reads as clarity. If a vocal is unclear, the answer is almost always somewhere from 2 to 5 kHz.
Pitch crowding in the low mids. Down at 220 Hz, one semitone is only about 13 Hz wide. Compare that to the top octaves, where a semitone spans 200 Hz or more. Because the notes sit so close together, aggressive saturation, clipping or modulation can reshape a waveform enough to smear one note into sounding like its neighbor. Go gentle with drive and modulated effects on low-mid parts.

Get the mids balanced and the whole mix opens up. Get them cluttered and no amount of bass or air will save it.

What are the five ugliest frequencies to cut?

Five ranges get cut on almost every session, so knowing them by ear covers most of the job:

Sub-30 Hz rumble. Wasted energy you can’t hear that eats headroom. High-pass it off nearly everything.
250 Hz mud. Low-mid buildup from many layers stacking. Cut a few dB on the guitars and bass that clog it.
450 Hz boxiness. A hollow, cardboard tone on drums and vocals. Sweep and dip the worst spot.
3.3 kHz harshness. The most fatiguing frequency there is, the pitch of sirens and smoke alarms. Tame the peaks.
6–8 kHz sibilance. The ice-pick “ess” on vocals and the scrape of picked strings. De-ess it.

Learn these five and you’ll fix 80% of a rough mix. The map above adds the rest: the 134 Hz boom, the 900 Hz honk, the 5 kHz bite, and the air up top. For the low end specifically, how to make your 808 hit hard covers where the kick and bass should sit so they lock instead of masking each other.

How do you know when you’ve cut too much?

You’ve cut too far when the mix loses warmth, weight or presence, and every problem band doubles as something you need. Mud lives right next to the body that makes a mix feel full and intimate. Harshness at 3.3 kHz is also intelligibility. Sibilance at 7 kHz is also the hi-fi sheen of a voice. Gut any of them and the mix goes thin, dull or lifeless.

Two habits keep you safe:

Cut narrow, and only as deep as the problem. For a resonance, use a tight band and pull it down until the ugliness goes, no further. When you high-pass the low end, push the filter up until the sound thins out, then back it off a touch.
Check on small speakers. 300 Hz is the lowest note many phone and laptop speakers reproduce, so if you scoop the low mids hollow, your bass vanishes on the devices most people listen on. What sounds clean on studio monitors can sound gutless on a phone.

For the harsh, sensitive bands, reach for a dynamic cut or a de-esser instead of a fixed one. It only pulls down when the frequency spikes, so you keep the presence the rest of the time instead of dulling the whole track.

Should you boost or cut?

Cut to fix a problem, boost to add character, and cut far more often than you boost. Subtracting a resonance is transparent because you’re removing something that was never supposed to be there. Boosting is additive, so it colors the sound and it can pile energy onto a band that’s already crowded. A useful shorthand: cut narrow, boost wide. A problem is usually a tight resonance you dip surgically; character is usually a broad shelf you lift gently, like the air above 12 kHz or the bite around 5 kHz.

One trap worth naming: saturation is a boost in disguise. When you saturate a part, it generates harmonics above whatever triggers it, so saturating a vocal fundamental at 220 Hz throws energy up into the mids at 440, 660 and beyond. That can add clarity on purpose (drive a band just below the 2–5 kHz formant and let the harmonics land in it), or it can clutter the mids by accident. Either way, listen to what it does above the band you’re pushing, not just the band itself.

What’s a fast EQ workflow?

Work from the bottom up and fix problems before you sweeten:

Clean the sub. High-pass everything except kick and bass around 30 Hz.
Clear the mud. On the parts that clog, cut a few dB between 200 and 400 Hz. Sweep to find the exact spot.
De-box. Dip the hollow 400–600 Hz resonance on drums and vocals if it’s there.
Make room in the mids. Carve a gentle dip around 1–2 kHz on busy backing parts so the lead sits forward without a volume boost.
Handle the harsh bands. Dynamic-cut 3.3 kHz and de-ess 6–8 kHz so you only touch them when they spike.
Sweeten last. Add bite near 5 kHz and a wide air shelf above 12 kHz to taste.

The single most useful move, at every step, is the sweep: put in a narrow boost, drag it across the range until the ugly resonance jumps out, then flip it to a cut. You’re finding the problem by ear, not dialing in a number you read somewhere.

Where the mix starts

The catch with all of this is that EQ only fixes what’s already recorded. A muddy arrangement stays muddy no matter how you carve it, so the cleanest mixes start from parts that already sit in their own space. Songen generates a full loop (lead, chords, bass and drums) in any of 50+ styles as editable MIDI, with instruments already chosen to fit the genre, so the frequencies aren’t fighting from the first bar. Generate a starting point, keep the parts that spark, and on macOS you can open any track in the piano roll and thin a busy part before it ever reaches your EQ.

From there, the moves above do the polishing. To hear these ideas on a full beat, how to mix a trap beat walks through the same decisions in context, and how to make better hi-hat rolls covers where the top end of a groove should sit. Learn the problem frequencies once, and you’ll hear them in every track you touch.

#mixing #eq #sound-design #production #beatmaking