What is reverb?

Reverb in plain English

Clap once in a stairwell. You hear the clap, and then you hear the stairwell: a burst of sound that rushes back off the concrete and fades over a second or two. Every room does this to some degree. Sound leaves the source in every direction, hits each surface, bounces, hits another surface and keeps going, losing a little energy every time, until there's nothing left to hear.

Your ears put all of that together without you noticing. A short, quiet wash says small room with soft furniture, while a long, bright one that swells up as it starts says big hall with hard walls. The level of the reverb compared with the original also tells you distance, which is why a voice with lots of reverb sounds like it's at the back of the room.

A reverb effect copies this. It takes a dry recording, made close to the microphone in a quiet room, and adds the reflections a real space would have added. Studios once did it with real rooms, steel plates and springs. Now it's mostly software, either working out the reflections with networks of delays or using a recording of a real space, and the lab on this page builds its spaces in code and runs them through your browser's own audio engine.

Early reflections and the reverb tail

Engineers split a reverb into two parts, because you hear them differently.

The early reflections are the first few echoes, the ones that bounced off a single surface on the way to you, such as the floor or the nearest wall. They arrive within the first 100 milliseconds or so, depending on the size of the room. Reflections that arrive within roughly the first 30 ms fuse with the original in your hearing, so you can't pick them out as echoes, but they change how the sound feels. They're how you can tell you're in a small bathroom with your eyes shut. The Haas effect lesson goes further into why.

After that, the reflections have bounced off several surfaces in turn, and there are so many of them, so close together, that they stop being separate echoes. That smooth wash is the tail, and it's the part most people mean when they say reverb. It fades away at a rate set by how big the space is and how much its surfaces absorb.

In a bigger room everything arrives later, because the walls are further away. Sound travels about 34 cm in a millisecond, so if you're standing next to the singer and the nearest wall is 5 metres away, its reflection travels 10 metres there and back and turns up around 29 ms after the direct sound. Drag the room size in the figure above and watch the spikes spread out. The early reflections lesson covers this part on its own.

Reading the lab

The cards along the top of the lab pick the kind of space. Under them, the big screen shows the whole loop: the pale shape is the dry sound at the level you're hearing it, and the coloured shape is the reverb it sets off. Wherever the colour carries on after a hit or a phrase has stopped, you're looking at the tail. Hover over any moment, or press and drag on a phone, to compare the two levels.

The screen underneath is the impulse response: what the reverb does to one click. It's the fingerprint of a space, and everything a reverb does to a sound follows from it. Height is level in dB. Time runs left to right, stretched at the start so the first few milliseconds have room, and you'll see an empty strip on the left for the pre-delay, amber spikes for the early reflections and a coloured slope for the tail. A pale line shows the top end on its own, above 4 kHz, so you can watch damping make it fall faster.

Both screens come from the same reverb you're hearing: the loop screen is your sound run through it and the impulse response is one click run through it, so when you change a control, both redraw from the new result. The Right now panel explains the control you last touched, with figures measured from that render, such as the time the tail takes to fall 60 dB and how loud the reverb is against the dry sound. The meters show the dry and wet levels and how much of what you hear is reverb.

A/B switches the reverb off and sets the dry sound to the same loudness, so you're comparing the space and nothing else. You can also upload your own file or record eight seconds with your microphone; it stays on your device and loops through the lab in place of ours.

The controls

Most reverb plug-ins have some version of these, whether it's Ableton's Reverb, Logic's ChromaVerb, FL Studio's Fruity Reeverb 2 or a hardware unit. Some hide them behind presets, and the names vary, but the ideas carry over.

Pre-delay

Pre-delay is a gap between the dry sound and the start of the reverb, set in milliseconds. In a real space it's roughly the time between the direct sound reaching you and the first reflections arriving, so a little pre-delay can make a space sound bigger.

It also keeps things clear. With no pre-delay, the reverb starts at the same moment as each word and smears its consonants. Set 40 ms and every word lands on its own before the space arrives, so the vocal stays close and readable while still sounding like it's in a hall. Push past 100 ms and the reverb begins to sound like a separate event, a little like an echo before the wash.

You can also time it to the song. At 120 BPM a quarter note is 500 ms, so a 64th note is 31.25 ms and a 32nd is 62.5 ms. The pre-delay lesson has more on choosing it.

Decay time and RT60

Decay, sometimes called reverb time or length, is how long the tail lasts. Most plug-ins measure it as RT60: the time it takes the reverb to fall by 60 dB once the sound stops. A decay of 2 seconds means that two seconds after the last note, the reverb is 60 dB quieter than it started, which is close to silent.

For a sense of scale, a furnished living room measures roughly half a second. Concert halls built for orchestras are usually around 2 seconds, and big stone churches can ring for several. In a mix, under a second sounds like a room, 1.5 to 3 seconds sounds like a hall or a plate, and anything longer starts to become an effect of its own.

The useful question is what happens in the gaps. A long decay fills the space between notes and phrases, which sounds lush on a slow ballad and messy on fast drums, because each hit's tail is still going when the next hit arrives. At 120 BPM a beat lasts 500 ms, so a 2.5 second decay keeps ringing for five beats. The lab's panel works this out for the loops, and the decay time lesson goes further.

Damping

In a real room, high frequencies die away sooner than low ones. Curtains, sofas, carpet, people and the air itself all soak up treble faster than bass. Damping copies that: it makes the top end of the tail decay faster than the middle.

In the lab, a 2 second hall with damping at 60% has everything above 4 kHz falling 60 dB in a little over a second, while the tail as a whole takes about 2.2 seconds. You can see it on the impulse response, where the pale line for the highs falls more steeply than the coloured line for the whole reverb. More damping sounds darker and further away, while too little sounds bright and a bit metallic, especially on long decays. Some plug-ins call this high damping, HF damp or treble decay.

Early reflections level

This sets how loud the early reflections are compared with the tail. Turning them up puts the sound closer to the walls of the room and makes the space easier to place; turning them down leaves mostly a smooth wash. On a drum room, strong early reflections are a lot of the sound. On a vocal they can make it sound boxy, so keep them low there.

Plates and springs have no walls, so they have no early reflections, and the lab greys this control out when you pick one.

Size and density

Size sets the distance between the walls. A bigger space spreads its early reflections further apart, and its tail takes longer to build to full density, because the echoes need more time to pile up. That slow swell at the start of a large hall is one of the clearest differences between a hall and a room, even at the same decay. On some plug-ins this is a separate density or diffusion control, and on others size and decay are tied together.

Low cut and high cut

These are filters on the reverb only, and the dry sound is untouched. A low cut, also called a high-pass filter, takes the bass out of the tail, which stops it piling up under the kick and bass. A high cut, or low-pass filter, takes out the fizz at the top and makes the reverb sit further back. There's more on filters in high-pass and low-pass filters, and the section on EQ further down covers how far to go.

Mix

Mix, also called dry/wet, sets the balance between the dry sound and the reverb. At 0% there's no reverb; at 100% there's only reverb and the dry sound has gone. On an insert you'll usually use something between 10 and 30%. On a send, covered below, the mix stays at 100% and you set the level with the send instead.

Watch the BAL meter and the wet against dry figure in the lab as you move it. At 30% mix on the vocal, the reverb sits about 10 dB under the dry sound, and it still sounds like plenty.

Room vs hall vs plate vs spring vs chamber

Reverb types are named after the spaces and machines they started as. Each has its own shape on the impulse response, so switch between them in the lab and watch it change.

Room

A small space with close walls: early reflections packed tightly into the first 30 ms or so, then a short, even tail. Rooms make something sound like it was recorded in a real place without sounding obviously reverberant. They're the usual choice on drums and acoustic guitars.

Hall

A large space modelled on a concert hall. The early reflections are spread out, the tail swells up slowly and the decay is long, usually 1.8 seconds and up. The lows tend to ring on a little longer than the mids, as they do in real halls. Halls suit strings, pads, ballad vocals and anything that should sound big.

Plate

A plate reverb was a sheet of steel, about one metre by two, hung in a frame with a driver to shake it and pickups to record the vibration. EMT's 140, from the late 1950s, is the famous one. Because a plate has no walls, it has no early reflections: the tail is dense and bright from the very first millisecond. That smooth, bright sound sits well on vocals and snares, and almost every reverb plug-in still has a plate setting.

Spring

A spring tank is two or three coiled springs in a metal box, with a driver at one end and a pickup at the other. Sound travels along the coils and bounces back and forth, and because a spring carries different frequencies at different speeds, each echo gets smeared into a chirp. That's the boing. Springs were built into Hammond organs and then guitar amps such as Fender's, which is why they're tied to surf guitar and dub.

Chamber

An echo chamber is a real room with hard walls, built for reverb: a speaker plays the sound in and microphones pick it up. Abbey Road and Capitol Studios in Hollywood both had well-known ones. Chambers sit between a room and a hall, with dense, bright early reflections and a tail that starts sooner than a hall's.

Modern plug-ins add more, such as shimmer and gated reverbs, and they're built on these. The plate vs hall vs room vs spring comparison puts them side by side, and algorithmic vs convolution reverb explains the two ways software makes them. A convolution reverb uses a recording of a real space's impulse response, often made by playing a sine sweep through a speaker and recording what comes back.

Should reverb go on a send or an insert?

An insert effect sits directly on a track, so the whole sound goes through it and the mix knob sets the balance. A send splits off a copy of the track's signal and routes it to a separate return track, where the reverb sits at 100% wet. The original carries on untouched, and the return fader sets how much reverb you hear.

Sends are usually the better choice for reverb. One reverb can serve the vocal and the snare at once, each with its own send level, so they all sound like they're in the same space. You can EQ the reverb on its own without touching the dry parts, and one reverb uses far less processing than eight. Ableton Live calls them return tracks and Logic calls them aux channels; in FL Studio you route a mixer track to another mixer track with the reverb on it.

An insert is fine when only one sound needs a particular space, like a spring on a guitar. Turn the mix down when you do, because a reverb on an insert at 100% wet removes the dry sound entirely. The insert vs send lesson covers both setups in detail.

How much reverb should you use?

More than sounds right in solo. With the track soloed there's nothing else playing to cover the tail, so a reverb at the right level sounds too wet; bring the rest of the mix in and the same amount can all but disappear.

A good working method is to set the reverb with the full mix playing, push it up until you can clearly hear it, then pull it back until you only notice it when you mute it.

Genre makes a big difference. A lot of modern pop and hip-hop keeps vocals fairly dry and close, with short reverbs or delays doing the work, while ambient music and shoegaze can be soaked in it. Listen to a few reference tracks in the style you're making and notice how long you can hear the tail after the last word of a line.

How to set up a reverb, step by step

This works for a vocal on a send in any DAW, and the same order works for most other sources.

1. Put the reverb on a return trackCreate a return or aux track, load the reverb on it and set its mix to 100%. Send the vocal to it, with the send post-fader so the reverb follows the vocal's level.
2. Choose the typeStart with a plate or a small hall for a vocal, a room for drums and guitars. Use a preset if you like; you'll change most of it.
3. Set the decay to the tempoPlay the busiest section and listen to the gaps. If the tail is still ringing when the next phrase starts, shorten it until it has mostly died away; for a vocal that usually lands somewhere between 1.5 and 2.5 seconds.
4. Add pre-delayStart at 20 ms and raise it until the front of each word is clear of the reverb, usually somewhere between 20 and 80 ms.
5. Filter the returnHigh-pass the reverb at 200 to 400 Hz and low-pass it at 6 to 10 kHz, or use the reverb's own low and high cut.
6. Set the level in the mixWith everything playing, raise the send until you hear the reverb, then back it off until you'd only notice it if it went.

Starting settings for common sounds

These are places to begin, chosen to be clearly audible. Your song's tempo and style decide where you end up.

EQ on the reverb return

Filtering the reverb is one of the quickest ways to make a mix sound cleaner, and it's easy to do on a send because the reverb is on a track of its own. Put an EQ after the reverb on the return track, or use the reverb's built-in low and high cut, which do the same job.

The low cut does most of the work. A reverb's tail is full of low end from the kick and the bass, and because it rings on for seconds, that low end piles up into mud. High-passing the return somewhere between 200 and 500 Hz removes it without touching the dry parts, which keep all their weight. Try step 8 of the lab on the drums, then drag the low cut down to 20 Hz to hear the kick blur.

The high cut is more a matter of taste. Rolling the top off at 5 to 10 kHz stops the tail fizzing on S sounds and cymbals and makes the space sound further away, which leaves the top end to the dry vocal. You can also cut a little around 2 to 4 kHz, where a reverb can compete with the clarity of a voice.

You can also duck the reverb. A compressor on the return, triggered by the dry vocal through its sidechain, turns the reverb down while the singer is singing and lets it bloom in the gaps. The sidechain compression lesson shows how to set one up.

Common reverb mistakes

Setting it in solo

A reverb that sounds right on a soloed vocal is almost always too quiet once the mix comes in, and one that sounds right in the mix sounds far too wet in solo. Make the decision with everything playing.

Leaving the low end in

Unfiltered reverb on a whole mix full of bass and kick turns into a low rumble, and what you notice is a muddy mix. Cut the lows from the return first and see how much it clears up.

A different space on every track

Eight reverbs on eight tracks, each with its own type and decay, can make the parts sound like they were recorded in eight different buildings. Start with one or two shared spaces on sends, such as a short room and a longer plate or hall, and only add more when a part really needs something else.

A long decay on a fast part

On fast drums or a busy vocal, a long tail fills every gap and turns the part into a wash. If the rhythm gets harder to hear when the reverb comes in, shorten the decay or use a delay instead.

Using it to hide a weak recording

Reverb makes things sound further away, and pushing a thin or out-of-tune performance into the distance rarely fixes it. It usually just makes the whole mix sound distant. Get the dry sound right first.

Training your ears to hear reverb

Long reverbs are easy to hear. The short ones take practice, because they mostly change how close and how big a sound feels. The quiz under the lab helps with both. It sets up a hidden reverb, covers the controls and the screens, and matches the loudness of every round, then asks whether the decay is short or long, or whether you're hearing a room, a hall or a plate. Your best score out of eight is saved in your browser.

When you're listening to a record, focus on the moment right after a sound stops: the end of a vocal line or the last hit before a break. That's where the tail is on its own and easiest to hear. Then listen for the start of each sound, where pre-delay and early reflections live.

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