Fundamental EQ Frequency Ranges

Why This Matters

When you're mixing a track, EQ isn't just about making things "sound better"—it's about understanding why certain frequencies create specific perceptions in the listener's ear. You're being tested on your ability to identify frequency ranges by their sonic characteristics, troubleshoot common mixing problems like muddiness or harshness, and make intentional decisions about where instruments should live in the frequency spectrum. These concepts connect directly to psychoacoustics, signal flow, and the physics of sound that form the foundation of professional audio production.

The frequency ranges below aren't arbitrary—they're divided based on how human hearing perceives them and what role they play in a mix. Don't just memorize the numbers; know what each range contributes sonically, what problems occur when it's mishandled, and which instruments naturally occupy that space. This conceptual understanding is what separates technical operators from skilled producers.

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The Foundation: Low-Frequency Energy (20-250 Hz)

Low frequencies provide the physical weight and power of a mix. These ranges are often felt as much as heard, and they're where most mixing problems begin—too much energy here creates mud, too little leaves a track feeling thin and weak.

Sub-Bass (20-60 Hz)

• Felt more than heard—this range creates physical impact and the sense of power in club systems and subwoofers
• Critical for EDM, hip-hop, and cinematic music where low-end weight defines the genre's sonic signature
• Primary cause of mix mud when overemphasized; requires high-pass filtering on non-bass elements to maintain clarity

Bass (60-250 Hz)

• Contains fundamental frequencies of kick drums, bass guitars, and synth basses—the rhythmic foundation of most tracks
• Groove and energy live here; this range drives the physical response listeners have to music
• Boominess occurs when multiple elements compete in this range; carving space through EQ cuts prevents frequency masking

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The Problem Zone: Low-Mids (250-500 Hz)

This range is notorious among engineers for causing issues. It adds essential warmth and body, but it's also where mud accumulates when multiple instruments stack their lower harmonics.

Low-Mids (250-500 Hz)

• Warmth and body originate here—vocals, guitars, and pianos rely on this range for fullness and richness
• Most common trouble spot in amateur mixes; the "boxy" or "muddy" quality usually lives around 300-400 Hz
• Subtractive EQ is your friend; small cuts across multiple tracks often work better than boosting elsewhere

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Clarity and Presence: Mid Frequencies (500 Hz-6 kHz)

This is where human hearing is most sensitive, which makes it crucial for intelligibility but also prone to causing listener fatigue when overemphasized. The ear naturally focuses here, so balance is everything.

Mids (500-2000 Hz)

• Vocal intelligibility depends on this range—the fundamental frequencies and lower harmonics of human speech live here
• "Nasal" or "honky" qualities emerge around 800 Hz-1 kHz when boosted excessively
• Most instruments have significant energy here, making it the most crowded part of the spectrum in dense arrangements

High-Mids (2-4 kHz)

• Attack and definition live here—the snap of a snare, the pick attack on guitar, consonants in vocals
• Presence and "cut" that allows instruments to punch through a mix without adding volume
• Listener fatigue zone; the ear is extremely sensitive here, so excessive boosts cause harshness over time

Presence (4-6 kHz)

• Clarity and articulation—this range helps distinguish individual elements and adds detail to the overall picture
• Sibilance in vocals (the harsh "s" sounds) typically occurs around 4-6 kHz and requires de-essing
• Harshness and brittleness result from overemphasis; surgical cuts often more effective than broad boosts

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Sparkle and Space: High Frequencies (6-20 kHz)

High frequencies add the finishing touches—air, shimmer, and the sense of space that makes a mix feel "open." These ranges contain relatively little musical information but dramatically affect perceived quality.

Brilliance (6-20 kHz)

• Sparkle and shimmer—cymbals, string harmonics, and the "sizzle" of distorted guitars live here
• Enhances perceived quality and "expensive" sound when properly balanced
• Brittle or harsh when overdone; can also emphasize noise, hiss, and recording artifacts

Air (10-20 kHz)

• Creates space and dimension—a subtle high shelf here adds openness without changing tonal character
• Psychoacoustic effect rather than musical content; listeners perceive "depth" and "room" from this range
• Age-related hearing loss affects this range first; mix decisions here should be verified on multiple systems

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Psychoacoustics and Perception

Understanding frequency ranges means nothing without understanding how humans actually hear. These concepts explain why mixing isn't just about measurements—it's about perception.

Fundamental Frequencies of Common Instruments

• Each instrument has a characteristic range that defines its tonal identity—kick drums (60-100 Hz), vocals (100 Hz-4 kHz), cymbals (3-15 kHz)
• Frequency masking occurs when two instruments share fundamental frequencies; EQ carving creates separation
• Knowing these ranges allows intentional arrangement decisions—choosing instruments that naturally occupy different spaces

Fletcher-Munson Curves (Equal-Loudness Contours)

• Human hearing isn't flat—we perceive mid frequencies as louder than lows and highs at the same SPL
• Mixing at different volumes changes perception; bass and treble seem to disappear at low listening levels
• Mix translation depends on this; understanding these curves explains why mixes sound different on various systems

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Quick Reference Table

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Self-Check Questions

1. Which two frequency ranges are most commonly responsible for "muddy" mixes, and what EQ technique addresses this problem?

2. Compare and contrast the high-mids (2-4 kHz) and presence (4-6 kHz) ranges—what does each contribute to a mix, and what problems arise from overemphasis in each?

3. If a vocal sounds "boxy" and lacks clarity, which frequency range would you cut, and which would you potentially boost? Explain your reasoning.

4. How do Fletcher-Munson curves explain why a mix that sounds balanced at high volume might seem bass-light when played quietly?

5. You're mixing a track where the kick drum and bass guitar are masking each other. Using your knowledge of fundamental frequencies, describe two EQ strategies to create separation between them.