Speaker Delay Calculator (Delay Towers and Fill Speakers)
The delay to give a closer fill or delay speaker so its sound arrives together with the main speakers, from the two distances and the air temperature.
Results
What this tool does
Sound covers a metre in about 2.9 ms in air at 20 °C, so a speaker 18 m closer to the audience than the mains would be heard about 52 ms early and sound like the main source unless it is delayed by that time. The speed of sound is c = 331.3 × √(1 + T/273.15) m/s, which grows by about 0.6 m/s for every degree, so a hot venue needs a slightly shorter delay. Engineers often add a few extra milliseconds, around ten, so that the sound still seems to come from the mains, which hear first; set that in the extra-delay field.
Formula
delay (ms) = (distance to mains − distance to fill) ÷ c × 1000 · c = 331.3 × √(1 + T ÷ 273.15) m/s
Variables
| Symbol | Meaning | Unit |
|---|---|---|
m | Distance from the main speakers to the listener | m |
f | Distance from the fill speaker to the listener | m |
t | Temperature | °C |
ex | Extra delay to keep the sound seeming to come from the mains | ms |
DL | Delay to set on the fill speaker | ms |
D0 | Delay from the travel time alone | ms |
C | Speed of sound at that temperature | m/s |
ST | Is the fill speaker nearer? | — |
Worked example
- Distance from the main speakers to the listener30 m
- Distance from the fill speaker to the listener12 m
- Temperature20 °C
- Extra delay to keep the sound seeming to come from the mains0 ms
- Delay to set on the fill speaker52.4 ms
- Delay from the travel time alone52.45 ms
- Speed of sound at that temperature343.2 m/s
- Is the fill speaker nearer?Yes: delay it by this amount
Limitations
- The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.