Q Factor (Bandwidth)
Definition
A parameter in parametric equalizers that controls the width of the frequency band being boosted or cut. A high Q value creates a narrow, surgical band; a low Q value creates a broad, musical shape.
In Simple Terms
How wide or narrow an EQ adjustment is. A wide Q gently shapes a broad range of frequencies—musical and smooth. A narrow Q surgically targets one specific problem frequency—precise but can sound unnatural if overdone.
In Practice
A narrow Q notch at 1.2 kHz surgically removes a resonance in an acoustic guitar recording without significantly affecting surrounding frequencies.
Common Confusion
Q is not a "size" knob — it is the inverse of bandwidth. Higher Q means narrower band, lower Q means wider. Different EQ plugins also normalize Q differently (some use the half-gain method, others half-power), so the same numeric Q can sound wider or narrower across tools.
Sources & Verification
- Bristow-Johnson, R. — Audio EQ CookbookW3C
- Bohn, D. A. — Bandwidth and Q Factor in EqualizersRane Note 170
- Smith, J. O. — Introduction to Digital Filters with Audio ApplicationsStanford CCRMA, 2007
Last verified: 2026-05-05