Pre-Delay

The wait between direct sound and reverb, and how it changes distance and the clarity of words.

Related

ReverbDelayVoice

The question

Pre-delay is often treated as a small gap before the reverb starts, so 20 ms gets dialled in without thought. It actually decides whether direct sound and space are heard as one event, and whether a vocal stays clear.

How it works

Pre-delay is the wait before a reverb begins to output. Within about 20 ms the reflection fuses with the direct sound, adding loudness and body. From roughly 30 to 60 ms the ear starts to separate them, the space seems larger and consonants stop being smeared by the tail. It does not change decay, only the timing relationship.

Settings and what you hear

Vocals often take 10 to 30 ms, keeping consonants while adding distance. On drums, 40 to 80 ms makes a room noticeably larger, but too short causes comb filtering with the direct sound and too long sounds like a separate event. Converting the value to a note length can produce rhythmic reflections.

What to listen for

Take one vocal line with pre-delay at 0, 30 and 60 ms and hear whether the s and t sounds are still covered by the tail. Stretch pre-delay on a snare and the room moves from close to behind.

Common misconceptions

That pre-delay is a delay effect; that longer always means bigger; that reverb should begin right against the direct sound.

Sources

• Välimäki, Parker and Savioja, Fifty Years of Artificial Reverberation, IEEE TASLP 2012 — pre-delay and early reflections checked, not quoted
• Huber and Runstein, Modern Recording Techniques, reverberation chapter — background checked, not quoted

Used for fact-checking only; all prose is original.