Reverb pre-delay and decay calculator
| Space | Pre-delay | Decay | Total |
|---|---|---|---|
| Tight1/4 note | 31.2 ms | 468.8 ms0.47 s | 500 ms |
| Medium1/2 note | 31.2 ms | 968.8 ms0.97 s | 1,000 ms |
| Large1 bar | 31.2 ms | 1,968.8 ms1.97 s | 2,000 ms |
| Huge2 bars | 31.2 ms | 3,968.8 ms3.97 s | 4,000 ms |
| Ambient4 bars | 31.2 ms | 7,968.8 ms7.97 s | 8,000 ms |
Decay is the note length minus the pre-delay, so the tail finishes right as the next note of that length begins.
For a reverb that breathes with the song, set pre-delay to a 1/64 or 1/128 note and decay to a note length minus that pre-delay. At 120 BPM: 31.25 ms of pre-delay and about 0.97 s of decay fills a half note.
What pre-delay does
Pre-delay is the gap between the dry sound and the start of the reverb. In a real room it is the time the first reflections take to arrive, which is why big halls have more of it. In a mix it is a separation control. A little gap lets the attack of a vocal or a snare land clean, then the room blooms behind it, so you can use more reverb without the source getting pushed back.
- 0 to 10 ms: the sound sits inside the space. Good for blending, pads, and shoegaze walls where you want no edges at all.
- 10 to 40 ms: the source stays in front and the consonants stay clear. A common starting point on vocals and snare. A 1/64 note at most tempos lands here.
- 40 to 100 ms and up: an audible gap, a slap of space before the wash. A 1/32 note lands here. Nice for dramatic vocals and big drums.
These are starting points, not rules. Set it, then listen to the attack of the source and move it until the front edge sounds clean.
Distance to pre-delay
Sound travels about 343 metres a second in air at 20 °C, so each millisecond of pre-delay is roughly 34 cm (about 1.1 ft) of extra path for the first reflection.
Pre-delay and decay for common tempos
| BPM | 1/64 pre | 1/32 pre | ½ note decay | 1 bar decay | 2 bar decay |
|---|---|---|---|---|---|
| 60 | 62.5 | 125 | 1.94 | 3.94 | 7.94 |
| 70 | 53.6 | 107.1 | 1.66 | 3.38 | 6.80 |
| 80 | 46.9 | 93.8 | 1.45 | 2.95 | 5.95 |
| 90 | 41.7 | 83.3 | 1.29 | 2.62 | 5.29 |
| 100 | 37.5 | 75 | 1.16 | 2.36 | 4.76 |
| 110 | 34.1 | 68.2 | 1.06 | 2.15 | 4.33 |
| 120 | 31.2 | 62.5 | 0.97 | 1.97 | 3.97 |
| 130 | 28.8 | 57.7 | 0.89 | 1.82 | 3.66 |
| 140 | 26.8 | 53.6 | 0.83 | 1.69 | 3.40 |
| 150 | 25 | 50 | 0.78 | 1.57 | 3.17 |
| 160 | 23.4 | 46.9 | 0.73 | 1.48 | 2.98 |
| 170 | 22.1 | 44.1 | 0.68 | 1.39 | 2.80 |
| 180 | 20.8 | 41.7 | 0.65 | 1.31 | 2.65 |
Should reverb be in time at all?
Timing the decay to the tempo stops tails piling up on each other, which is most of what makes a mix sound muddy. It matters most on sparse, rhythmic material. On ambient and shoegaze the opposite can be true: a decay far longer than the bar, no pre-delay, and the reverb louder than the source is the sound. Use the table for the first and ignore it for the second.
Adrift is a reverb with two knobs.
No pre-delay field, no decay field. HEAT for warmth, MELT for how far the sound dissolves, FREEZE to hold it. Built for the shoegaze end where the reverb is the song. Play it in your browser first.
Play Adrift live →Quick answers
What is reverb pre-delay?
Pre-delay is the time between the dry sound and the start of the reverb. A short gap keeps the attack of the source clear so it stays in front of the reverb instead of being washed into it.
How do I calculate pre-delay from BPM?
Work out a quarter note in milliseconds (60,000 ÷ BPM), then divide: by 16 for a 1/64 note, by 32 for a 1/128 note. At 120 BPM a 1/64 note is 31.25 ms.
How long should my reverb decay be?
For a reverb that sits in time, take a note length (a quarter note, half note or bar) and subtract the pre-delay. At 120 BPM with a 1/64 pre-delay, a half-note decay is about 0.97 seconds and a one-bar decay about 1.97 seconds.
What pre-delay should I use on vocals?
Somewhere around 10 to 40 ms is a common starting point because it keeps consonants clear while the reverb blooms behind the voice. Move it by ear until the front edge of the vocal sounds clean.
How many milliseconds of pre-delay per metre?
About 2.9 ms per metre (0.9 ms per foot), because sound travels about 343 metres a second in air at 20 °C.
More free music tools
Online guitar tuner
Tune guitar, bass or ukulele with your mic. Finds the string for you, in standard or drop tunings.
Song key and BPM finder
Drop in a song to get its key, Camelot code and tempo, with harmonic mixing matches.
LUFS meter
Integrated loudness, true peak and loudness range, and what Spotify, Apple Music and YouTube will do to your master.
Chord finder
Click notes on a piano to name any chord or slash chord, or build a chord and hear it.
Online tone generator
Any frequency, sweeps, and white, pink and brown noise. Test speakers, subs and left and right.