Group Delay Graphs
Illustration in preparation Description: Group delay (ms) vs frequency graph showing: peaked group delay at subwoofer resonance (~2 ms), flat group delay in midrange, slight rise at tweeter crossover; dashed line at 10 ms labeled "audibility threshold for most listeners"
Group delay is the time delay as a function of frequency. Constant group delay = no time distortion. Frequency-dependent group delay = different frequencies arrive at different times.
Audibility thresholds (from research):
- Below 500 Hz: Group delay up to 15–20 ms generally inaudible
- 500–2000 Hz: Audible above 5–10 ms
- Above 2000 Hz: Audible above 1.5–3 ms
Bass frequencies (below 100 Hz) tolerate much more group delay — the long wavelength prevents temporal resolution. High frequencies are most sensitive.
Causes of high group delay:
- Sharp (high-Q) low-frequency resonances
- Ported enclosure below tuning frequency
- Sharp digital crossover filters
- Room modes at bass frequencies