DJ Toolkit
Creative All creative tools

Reverb Tail Advisor

Reverb isn't a knob — it's a time window that has to fit inside your bars. Too long and your snare smears into the next downbeat; too short and your vocal sits flat. This tool draws the decay envelope of your reverb over a bar-grid that scrolls at your chosen BPM, then tells you whether the tail fits, whether you need more pre-delay, and whether the low end needs sidechain ducking.

Reverb settings

Decay envelope vs. bars

Wet envelope Dry hit

Each vertical line is one bar; the fuchsia curve is the wet-tail energy in dB relative to the dry hit.

Sidechain duck preview

The ducking envelope ducks the reverb ~6 dB on every kick and recovers in 300 ms. Adjust in your DAW until the wet level sits ~12 dB below the dry between hits.

How to use

  1. Set your Project BPM first — the bar-grid on the canvas depends on it.
  2. Pick the Style preset that matches the room you're trying to evoke, then fine-tune the Decay slider.
  3. Set the Pre-delay. For vocals, 20–40 ms keeps the dry signal upfront; for atmospheric pads, 60–100 ms gives you a sense of distance.
  4. Toggle Sidechain duck on for any reverb that sits on a kick-heavy track (house, techno, dnb, trap) and watch the duck preview.
  5. Read the verdict box. If it says "tail bleeds into next bar" the decay is too long — drop it under the bar length. If it says "tail fits" you're in the sweet spot.

How to read the result

The horizontal axis is time in seconds; the vertical axis is the wet-tail level in dB relative to the dry hit. Each tall grey vertical line is a bar boundary. The cyan dot on the left is the dry transient (kick, snare or vocal onset); the fuchsia curve is what the reverb tail looks like as it decays.

The rule of thumb the visual enforces: the tail should be at least 30 dB down by the next bar boundary. If the fuchsia curve is still above that line when the next vertical grey line hits, the reverb will mask the next transient and your mix will sound washy.

The duck preview below shows the same envelope with sidechain engaged: the wet level drops sharply on each transient (the downbeats) and then recovers in the time printed on the readout. If the recovery is shorter than the bar length you'll hear a "pumping" effect, which is desirable in EDM and undesirable in jazz ballads — match the recovery time to the genre.

Limitations

The decay curve is an idealised exponential. Real algorithmic reverbs (convolution, plate, spring) have early-reflection patterns and a non-exponential tail; this tool won't reproduce the slap-back of a real plate or the metallic ringing of a cheap spring. Use your ears for the character, the maths for the length.

Pre-delay recommendations assume a typical pop/dance arrangement. For ambient or classical contexts you want pre-delay much higher (120–250 ms) to create a sense of space between the dry source and the first reflection.

The duck preview uses a fixed 6 dB duck depth. Most DAW stock compressors let you push deeper (10–18 dB) when the source is a vocal or a snare instead of a kick.

The bar-grid is 4/4 only. If your track is in 3/4, 6/8, 7/8 or any other meter, the bar boundaries drawn here will be wrong. Multiply by your true bar length before committing.

FAQ

Why is cathedral decay so much worse at 140 BPM than at 90 BPM?
Because the bar length shrinks as BPM goes up. At 90 BPM, one bar is 2.67 s — a 4 s cathedral tail fits comfortably. At 140 BPM, one bar is 1.71 s — the same 4 s tail bleeds across almost two and a half bars. Either drop to a hall preset, shorten the decay, or use heavy sidechain ducking.
Should I always duck the reverb on the kick?
On kick-heavy EDM (house, techno, dnb, trap, future-bass) yes, almost always. On genres where the kick is soft (singer-songwriter, indie, jazz, ambient) ducking the reverb on the kick will make the reverb sound choppy and weird — duck it on the vocal or the snare instead, or don't duck at all.
What's the difference between decay and "tail length"?
Decay (or T60) is the time it takes the wet signal to drop 60 dB — basically, the time for the reverb to become inaudible. Tail length in producer-speak is usually the time it takes to drop 20–30 dB, which is what the audience actually hears. This tool shows the 30 dB tail because the 60 dB decay is rarely musical — by 30 dB the reverb is already masked by the next transient.
My reverb sounds great in solo but muddy in the mix. Why?
Three common causes: (1) decay too long for the BPM (use this tool to check); (2) pre-delay too short, so the reverb fights the dry source (raise it 10–20 ms); (3) low-end content in the reverb — most stock reverbs ship with a "low cut" or "damping" knob; raise it to 200–400 Hz to keep mud out of the sub.
Can I use this for a sends-bus reverb and an insert reverb?
Yes — the maths is the same. The only difference is that on a send reverb you control the wet level with the send fader instead of the wet/dry knob, and the dry signal is always 100% present in the channel. Set the wet level to taste, then check the verdict box again.
Advertisement