A parametric equalizer allows independent control of center frequency, gain, and bandwidth (Q) for each band

A fully parametric equalizer provides three independent controls per band: center/knee frequency (continuously adjustable), gain (cut or boost in dB), and Q (bandwidth factor — high Q is narrow, low Q is wide). Q = center frequency ÷ bandwidth in Hz. A high Q (e.g., Q=10) produces a very narrow notch/peak; a low Q (Q=0.5) produces a broad shelving-like curve. Parametric EQ can perform any function of a graphic EQ plus narrow notching, precise feedback control, and broad tonal shaping with minimal bands. The tradeoff is that setting a parametric requires more skill — three parameters must be adjusted rather than one slider — and settings are harder to document visually. Only EQ that controls all three parameters is truly ‘fully parametric’; some ‘parametric’ designs have fixed Q.

Examples

To remove a 3.2 kHz feedback tone, a parametric EQ band is swept to 3.2 kHz, Q set to 8, and gain set to –8 dB. Only a very narrow frequency range is affected. A graphic EQ would require cutting the entire 2.5–4 kHz range.

Assessment

Compare a 1/3-octave graphic EQ notch at 2.5 kHz to a parametric notch at 2.5 kHz with Q=10 in terms of frequency selectivity and which adjacent frequencies are affected.