Sound takes 3 ms per metre. Your visuals do not.

The number: about 3 milliseconds per metre

Sound travels through air at roughly 343 metres per second. Turn that around and you get the number worth memorising: sound needs about 3 ms to travel one metre. Light, for our purposes, arrives instantly.

So when you fire a visual on the kick, two things leave at the same time and arrive at different times. The image reaches every eye at once. The sound does not.

What that means in a real room

• A small club, 15 m deep: ~44 ms of drift at the back wall. Borderline noticeable.
• A mid-size venue, 30 m: ~87 ms. Clearly visible if the cut is sharp.
• A big stage, 60 m to the sound desk: ~175 ms. That is more than a sixteenth note at 128 BPM.

And the drift always goes the same way: the visual arrives early for anyone who is not standing where the sound was captured. The people at the front are fine. The people at the back see the flash before they hear the hit.

Why it is worse than it sounds

A human can spot audio and video out of sync at surprisingly small offsets — and we are far more forgiving when the sound arrives first than when the image does. A late sound reads as distance, which our ears expect. An early image reads as wrong.

That is exactly the case here. The visual is the one that arrives early. So the drift lands on the side our brains like least.

What you can actually do

You cannot make sound faster. What you can do is hold the visual back by the same amount, so both land together where the crowd actually is.

The rule of thumb: pick the distance from the speakers to the middle of the crowd — not to the back wall, not to your booth — and delay the visuals by 3 ms for every metre. A 30-metre room, crowd centred around 15 m: about 45 ms.

LumaDeck Pro has that offset as a setting you dial in per venue, and it stays with the venue so the next time you play there it is already right. If your tool does not have it, you can approximate it by nudging your cue points — worse, but better than nothing.

The part nobody tells you

This only matters if the rest of your chain is honest. If your visuals are already drifting because the tempo is being guessed from a microphone, a 45 ms correction is noise on top of noise. Get the tempo right first; then correct the room.