Reverb predelay sets a gap between dry attack and reverb onset that controls clarity and perceived distance

Predelay is a short delay applied to the reverb signal so its onset arrives after the dry source. This lets the listener hear the source’s attack cleanly before ambience arrives, so the source stays defined instead of being washed out. Predelay serves two further purposes: it reduces comb-filtering (phase cancellation) between the wet and dry signals, which occurs when they are very close in time; and it controls perceived front-back distance. With no predelay the source sounds ‘stapled to the back wall’ of the virtual room and distant; adding predelay pulls it forward and more intimate, and longer values imply bigger spaces. Because predelay reduces masking of the wet signal by the dry, you can use less reverb overall and keep more clarity. Typical starting values are around 10-40 ms, shorter for smaller spaces, then refined by ear. Predelay can be timed to tempo (e.g. a fraction of the smallest delay value). A common misreading is that decay length alone determines integration; predelay often matters more for whether a reverb feels like it belongs to the source.

Examples

A vocal with no predelay sounds distant and swamped; adding ~15-20 ms separates it from the reverb onset, pulls it forward and present, and lets you turn the reverb down. Tempo-timed: if a 1/16-note delay at 105 BPM is 143 ms, a predelay of 143/4 ≈ 36 ms. To make reverb stand out or sound more distant, use little or no predelay (or a random, untimed value).

Assessment

Explain why a 2 s reverb with 0 ms predelay often sounds worse than the same reverb with 20-25 ms predelay even at equal decay, covering both masking/clarity and perceived distance. Give a typical starting value, then calculate the predelay for a 1/16-note timing at 90 BPM.