Guides

Reverb Decay and Wet Mix Explained for Slowed and Reverb Edits

2026-10-11

What the Reverb and Space sliders really do, why pre-delay is fixed at 10 ms, how the tail darkens over time, and how decay interacts with tempo, with tables of settings.

Every slowed + reverb editor has a reverb control, and most of them have exactly one: a single slider from "a bit" to "a lot". This editor has two, and the split is deliberate. Reverb is the wet mix, how much of the processed signal you hear. Space is the decay, how long the tail takes to die. They sound similar when you nudge them, and they are not the same thing at all.

If you have ever made an edit that was simultaneously too wet and too small, or one where the words were clear but the room felt like a cupboard, you ran into the difference. This guide explains what each control does inside the add reverb to song tool, what the fixed parameters are and why they are fixed, and how decay and tempo interact once you slow a track down. It is longer than it needs to be for someone who just wants a number; the tables are there for that reader.

What a convolution reverb is

The reverb here is a convolution reverb. In plain terms, it takes a recording of how a real or synthetic space responds to a single sharp sound, called an impulse response, and applies that response to every sample of your song. The result is the song played in that space.

Convolution reverbs sound natural because they are based on actual acoustic behaviour rather than a network of delay lines approximating it. The trade-off is that they are heavier to compute, which is why live preview can stutter on an old phone while the export, rendered offline, is always clean.

The two sliders control two different aspects of that process.

Reverb: the wet mix

Reverb runs from 0 to 100%. At 0 you hear only the dry signal. At 100 you hear only the wet signal, the reverb output with none of the original. In between, the two are blended.

This is the control that determines how far away the song feels. A low mix is a singer in front of you in a reverberant hall. A high mix is a singer at the far end of it.

What the mix does not change is the character of the room. The tail is the same length and the same colour at 20% and at 70%. There is simply more of it in the blend.

Some reference points:

A point that catches people out: the mix is a blend, not an additive layer. Raising Reverb from 40 to 60% does not add 20% more reverb to a constant dry signal; it also pulls the dry signal down. That is why a high mix makes the vocal quieter as well as wetter.

Space: the decay time

Space runs from 1.2 to 6.0 seconds and sets how long the reverb tail takes to fall away. Technically the number describes the time it takes the tail to drop by 60 dB, which is the standard way rooms are measured. In listening terms, it is how long the room keeps ringing after a sound stops.

Short decays feel like small rooms: a bedroom at 1.2 s, a tiled bathroom or a club at 1.8 s. Medium decays feel like halls and churches: 2.4 to 3.5 s. Long decays, 4 to 6 s, are cathedrals and caverns, spaces where a clap takes a visible moment to fade.

The decay changes how the reverb interacts with rhythm, which is the heart of the next section.

Why mix and decay are different problems

Imagine a vocal line, then a gap, then the next line. The reverb tail of the first line spills into the gap. Whether it also spills into the second line depends on decay, not mix. A 2.4 s tail at any mix level is mostly gone before a line that starts three seconds later. A 5 s tail at any mix level is not.

Now imagine two lines with no gap. The tail of every syllable overlaps the next syllable regardless of decay, because there is no space for it to clear. Here, mix is everything: at 30% the overlap is a soft halo, at 60% it is a smear.

So:

• Words blurring together inside a line: too much mix. Lower Reverb.
• The tail from one line ringing through the next: too much decay. Lower Space.
• The room feels small even with lots of reverb: decay is too short for the mix. Raise Space and lower Reverb.
• The room feels distant and vague: mix is too high for the decay. Lower Reverb, maybe raise Space.

The muddy edits guide uses this distinction as the first step in its diagnosis.

The fixed parameters

A full reverb plugin exposes a dozen parameters. This editor fixes several of them so the two you have are more useful. Being open about what is fixed and why:

Pre-delay: 10 ms

Pre-delay is the gap between the dry sound and the start of the reverb. It is fixed at 10 milliseconds. That is short enough that the reverb feels attached to the source rather than echoing after it, and long enough that the very first transient of each note gets through clean before the tail arrives. 10 ms is a common choice in mixing for exactly this reason: it keeps the attack of a vocal or a drum hit intelligible without sounding like a separate slap.

Longer pre-delays, 40 to 80 ms, are a mixing technique for pushing a vocal forward in a wet mix, and some slowed edits would benefit from it. You cannot do that here. If you need it, a DAW is the tool.

High-frequency damping

Real rooms absorb high frequencies faster than low ones. Air, carpet, bodies and curtains all soak up treble. So a reverb tail does not just get quieter over time; it gets darker. The first reflections contain the full spectrum, and by the end of the tail only the low mids and lows are left.

The convolution reverb here has that damping built into the impulse response. You do not set it, but you should know it is there, because it explains two things:

1. Long Space values sound darker than short ones at the same mix. The tail has more time to lose its highs.
2. The Tone control, which is a high shelf on the whole signal, interacts with the damping. A negative Tone plus a long Space stacks two sources of darkness. That is the recipe for mud.

If you want a long, bright tail, you need Tone at 0 or slightly positive to counter the damping. If you want a dark, close sound, a short Space with negative Tone gets there without losing definition.

Decay and tempo

Here is where slowed editing gets interesting. Reverb decay is measured in seconds. Music is measured in beats. When you slow a song, the beats get further apart but the decay, set in seconds, does not change. So the same Space value covers fewer beats at a slower speed.

Take a song at 120 BPM with a 2.4 s Space. One beat is 0.5 s, so the tail spans almost five beats, more than a bar. Slow the song to 0.80x and it is at 96 BPM, one beat is 0.625 s, and the same 2.4 s tail spans under four beats. The reverb feels shorter relative to the music, even though nothing changed in seconds.

This has a practical consequence: as you slow a song down, you can raise Space without the tail getting musically longer. Many people find that the "right" decay rises roughly in step with how much they slowed the track.

The right-hand column is a useful anchor. A decay roughly equal to one bar of the slowed song gives you a tail that connects each bar to the next without piling up. Longer than two bars and the tail becomes a drone under the song. Shorter than half a bar and the reverb reads as a room rather than a space.

You do not have to calculate this. The ear does it well. But if an edit feels "off" in a way you cannot name, check whether the decay is fighting the tempo.

Settings that work together

Notice how Haze Chamber and Wave Drift get their very different characters from opposite choices: one with a high mix and tiny decay, the other with a slightly lower mix and a long decay. Same reverb, two sounds.

Common misunderstandings

"More Space makes it wetter." No. Space makes it longer. A long tail at a low mix is still mostly dry.

"I should set Reverb first." Set speed first, then Space, then Reverb. Decay has to fit the slowed tempo; mix is the final balance.

"The reverb is making it dark." Partly. The tail darkens over time by design. But if the whole signal is dark, that is Tone, and the two stack.

"100% Reverb should sound huge." It sounds distant. At 100% there is no dry signal, so there is no attack, and without attack there is no sense of size, only haze.

Limits of the two-slider approach

Being honest about what you give up compared with a full reverb plugin:

• No adjustable pre-delay. Fixed at 10 ms.
• No damping control. Built into the impulse response.
• No choice of room type. One hall-like space.
• No separate EQ on the reverb return. Tone affects the dry signal and the wet signal together.
• No ducking or sidechain, where the reverb drops while the vocal sings.

For most slowed + reverb edits none of these matter. For a release-quality mix where the reverb has to sit precisely around a vocal, they do, and a DAW is the right tool. The reverb generator page is the editor with reverb as the focus if you want to experiment with just these two controls on a dry track.

Open the free editor: upload MP3, WAV, AAC, OGG or FLAC, adjust speed, reverb, bass, tone, width and space, then export MP3 or a ZIP of many tracks. Everything runs in your browser.