Delay Calculator
Distance, milliseconds and samples, with temperature-adjusted speed of sound. For speaker alignment, subwoofer delay and delay tower time alignment.
Conditions
Convert: enter any one value
Subwoofer alignment
When mains and subs are physically separated, delay the closer source to align wavefronts at the audience.
Delay tower alignment
Measure both distances to the same audience position inside the tower's coverage. The Haas margin keeps the main PA arriving first, so the image localises to the stage.
Frequency and distance
Type a frequency to get its wavelength, or a distance to get the frequency that wavelength corresponds to. All three fields are linked and use the speed of sound above.
Half-cycle distance gives the first cancellation frequency for that path length difference: two sources 0.85 m apart in path length cancel near 200 Hz.
How Speaker Delay Works
Sound travels at approximately 343 m/s at 20°C, but this changes with temperature. Every 1°C change alters the speed by ~0.6 m/s. At 30°C, sound travels ~349 m/s; at 10°C, ~337 m/s. That's a 3.5% difference, enough to misalign a PA by several milliseconds over typical throw distances.
The Formula
Speed of sound (m/s) = 331.3 × √(1 + °C/273.15) × (1 + 0.00032 × %RH)
Delay (ms) = Distance (m) / Speed of Sound (m/s) × 1000
Delay (samples) = Delay (ms) × Sample Rate (kHz)This matches the Cramer (1993) / ISO 9613-1 formula used in the calculator. Humidity effect is a simplified approximation.
Why Temperature Matters
Outdoor festivals: morning soundcheck at 12°C vs show at 28°C = ~2.5 ms difference at a 30m throw. That's a quarter wavelength at 100 Hz, enough to start causing comb filtering and reduced sub-bass impact if you don't recalculate.
Practical Rules of Thumb
- 1 ms ≈ 34.4 cm (at 20°C, 50% RH)
- 1 ft ≈ 0.88 ms (at 20°C)
- 1 sample @ 48 kHz = 0.0208 ms
- Comb filtering becomes significant when misalignment exceeds ~¼ wavelength (~3 dB cancellation). Full nulls occur at ½ wavelength.
Subwoofer Alignment
Subs are often physically behind mains (cardioid, end-fire) or in front (ground stacked). Measure the acoustic center of each source to the primary audience area. Delay the closer source by the path length difference. For precision, measure with Smaart/SysTune: impulse response gives exact delay.
This distance-based calculation gives a geometric starting point. Subwoofer alignment should always be verified with transfer function measurement (e.g., Smaart, SysTune) because subs have significant processing delay and frequency-dependent acoustic centers that distance alone cannot account for.
Delay Tower Alignment
Standard procedure: Measure distance from main PA to the delay tower's coverage area, and from the delay tower to the same point. Set delay = ((Distancemain − Distancetower) / Speed of Sound × 1000) + Haas margin (10–20 ms). The Haas margin ensures the main PA arrives first, localizing the sound image to the stage. If the total delay exceeds ~35 ms, the tower may be perceived as a distinct echo.
Frequently Asked Questions
What sample rate should I use?
Use your console/interface native sample rate. Most live desks run 48 kHz or 96 kHz. If you're sending audio across a Dante/AES67 network, ensure your delay processor's sample rate matches the network, as these networks do not natively handle sample rate conversion. The physical delay time (ms) remains constant regardless.
Does humidity really matter?
Minor effect: at 20°C, the real-world humidity effect is roughly 0.1–0.15 m/s per 10% RH, or about 1–1.5 m/s total across the full 0–100% range (~0.4%). This calculator uses a simplified linear approximation that slightly overestimates the effect but remains negligible for practical live sound alignment. For sub alignment it's negligible; for precision studio work, use a measurement mic.
How do I find the acoustic center of a speaker?
For a single driver: it is typically near the dust cap or between the voice coil and the cone apex, though it varies slightly by frequency. For multi-way: the acoustic center is typically between the drivers, weighted by crossover. For line arrays: use the manufacturer's specified acoustic center (usually geometric center of the array). When in doubt, measure with Smaart/SysTune: impulse response gives exact delay.
What about delay towers / fills?
See the Delay Tower Alignment section above. The tool calculates geometric delay and adds your Haas margin automatically. The tower delay result includes both components.
Can I use this for studio monitor alignment?
Yes. Nearfield distances are shorter (1–2m), so errors are smaller, but the principle is identical. Many monitor controllers accept delay in samples. This tool converts for you.
What's the difference between geometric delay and Haas aligned delay?
Geometric delay = pure distance/speed of sound time. Haas delay = geometric + 10–20 ms so the primary source arrives first. For subs aligning to mains: usually just geometric (whichever is closer). For delay towers: always add Haas margin so the stage (main PA) localizes the image.