Graphic Equalizer
Definition
Graphic Equalizer
A graphic equalizer uses a bank of fixed-frequency filters with adjustable gain sliders, providing a visual representation of the frequency response adjustment. The standard 31-band graphic EQ uses ISO 1/3 octave center frequencies from 20 Hz to 20 kHz. While simpler to operate than parametric EQ, graphic EQ has fixed center frequencies and bandwidths that may not align with actual problem frequencies. SonaVyx visualizes the effect of graphic EQ settings on the measured response.
How It Is Measured
Graphic EQ effectiveness is verified by measuring the transfer function with SonaVyx before and after adjustment. Each slider position corresponds to a fixed band-pass filter centered at a standard 1/3 octave frequency. SonaVyx RTA display in 1/3 octave mode provides a direct visual comparison between the graphic EQ slider positions and the measured system response at those frequencies.
Practical Example
A 31-band graphic EQ is used to flatten a PA system response in a hotel ballroom. SonaVyx RTA shows excess energy at 160 Hz and 200 Hz. The engineer pulls the 160 Hz slider down by 4 dB and the 200 Hz slider down by 3 dB. Re-measurement confirms the correction, but the EQ also introduces a slight dip at 180 Hz between the two bands — a limitation of fixed-frequency graphic EQ that parametric EQ would handle more smoothly.
31-Band vs 15-Band
A 31-band graphic EQ uses 1/3 octave spacing, providing one slider per third-octave band. A 15-band uses 2/3 octave spacing with half the resolution. For system tuning, 31-band offers sufficient resolution to address most frequency response problems. However, if the actual problem falls between two slider frequencies, neither adjacent slider can precisely correct it — this is the fundamental limitation compared to parametric EQ.
Filter Interaction
Adjacent graphic EQ bands interact, creating combined responses that differ from what individual slider positions suggest. Pulling three adjacent bands by -6 dB does not produce a flat -6 dB notch — the combined response has a broader, shallower shape. Modern constant-Q graphic EQ designs minimize these interactions, but they remain a consideration when precise correction is needed.
When to Use Graphic vs Parametric
Graphic EQ is appropriate for broad tonal shaping, quick system corrections where exact frequency targeting is not critical, and situations where operators need a simple, visual interface. Parametric EQ is preferred for precision corrections, feedback notch filters, crossover alignment, and situations where the problem frequency does not coincide with a standard 1/3 octave center. SonaVyx measurement data guides the choice.
Try It Now
Verify graphic EQ settings — free RTA analysis in your browser