EQ Q-Factor Calculator
When tuning an audio system with a Parametric Equalizer (PEQ), you need to convert target cutoff frequencies into a specific Center Frequency and Q-Factor. Use this calculator to quickly convert your low and high target frequencies into exact DSP parameters.
Band Frequencies
Center Frequency (fc)
141.42Hz
Bandwidth (BW)
100.00Hz
Q-Factor (Q)
1.41
Q-Factor Reference Guide
Use this table to understand what your calculated Q value means when applied to a DSP PEQ band.
| Q Range | Filter Type | Best Used For |
|---|---|---|
| > 2.5High Q | Narrow notch / peak | Surgical fix of sharp vehicle resonances or cabin spikes without affecting surrounding frequencies. |
| 1.0 – 2.5Medium Q | Moderate bandwidth | Ideal for general tonal balancing and smoothing out room/cabin response curves. |
| < 1.0Low Q | Wide, gentle slope | Broad tonal shifts across whole octaves (e.g., overall treble roll-off or broad bass warmth). |
Understanding Parametric EQ Parameters
A parametric EQ band is defined by three parameters: Center Frequency (fc), Gain (dB), and Q-Factor. Unlike a graphic EQ where bands are fixed, a PEQ band on a DSP lets you place an adjustment exactly where you need it and control how wide or narrow that adjustment is.
The Center Frequency is calculated as the geometric mean of your target low and high frequencies: fc = SQRT(f_low × f_high). Human hearing is logarithmic, so the geometric mean places the center at equal perceptual distance from both band edges — not the arithmetic midpoint.
Bandwidth (BW) is simply the difference between your high and low target frequencies. A wider bandwidth means more frequencies are affected by the EQ adjustment.
Q-Factor is the ratio of center frequency to bandwidth: Q = fc / BW. A Q of 1.0 means the affected band spans one octave on each side. A Q of 6.0 produces a very narrow notch used in Room Correction software for precise room mode suppression.
When correcting car audio systems using a measurement microphone and software like REW or OmniMic, measure the frequency response, identify the resonant peak or dip, read off its upper and lower −3 dB points, enter them here, and copy the calculated fc and Q directly into your DSP software.