Digital reverb is an important tool in music production that can be used to create space in your sounds by emulating natural sound reflections that occur in real life. Digital reverbs are used all the time in modern productions and many of your favorite reverb are quite possibly digital, digital emulations, or algorithmic reverbs. In this article, we’ll break down digital reverb, what it is and how you can use it to improve your music.
What Is Digital Reverb? (TL;DR)
Digital reverb uses a mathematical algorithm to re-create the sound reflections that are found in natural reverberation. When you clap in a cave, the reverb is a product of multiple sound reflections hitting your ear at delayed times. Digital reverb creates the effect using feedback loops and delays, creating artificial spaces.
With digital reverb, you can alter any parameter such as size, decay, pre-delay, and more. Digital reverbs (especially algorithmic reverbs) allow you to create spaces that would never be possible in real life. This is great for electronic sound design.
They are also often software, or pedal devices that are compact and easy to transport, making the cost extremely low, the CPU usage low and were invented to replace the cumbersome plate, spring and reverb room options.
Digital reverb can’t replicate natural reverb perfectly, but algorithmic reverbs are getting good at replicating the sound. This is the same with analog recreations of hardware and analog synths – they almost sound identical to the untrained ear.
Digital reverbs emulate the sound by adding a lot of variation in delays, and the sound reflections created, so they sound similar to natural reverb, which is unpredictable sound reflections all over the place.
This variation makes it sound extremely close to the real thing.
One con of digital reverb is if you don’t know how to set it up, it can sound awful in the mix, and completely ruin a mix.
There are 2 types of digital reverb – we’ll run you through them now.
The Two Digital Reverb Types Explained
Algorithmic reverb uses a mathematical algorithm to re-create natural-sounding reflections using a lot of delayed copies of the signal it is fed. They are the most common digital reverb and are mostly used for situations where CPU power isn’t available and are commonly used for electronic sound design scenarios.
Algorithmic reverb is also commonly used in a studio setting when a vocalist needs reverb in their headphones, but the engineer doesn’t want to take up much CPU (recording is an intensive process).
These repeats of the original signal are continuously fed back through more loops and are controlled using the decay, size, and other controls found on the unit.
The longer the decay of a signal, the more feedback loops and copies are needed.
Algorithmic reverbs can additionally use modulation such as chorus to further differentiate the signal and make it sound more natural to the human ear. There are additional controls like brightness, which can elongate the decay of higher frequencies to create brighter tones.
The reverb units allow for a great deal of creativity and give produces the option to create reverbs that would not be possible to replicate in real life.
Convolution reverbs are digital reverbs that use an Impulse Response to create a natural-sounding space. They take a recording using microphones, of a sine wave or starter pistol in the desired space. You can open this IR in a convolution reverb, and it will process it to remove the sound and apply the reverb to your track.
It has extremely high processing power, and uses a lot of CPU, so engineers rarely use a lot of convolution reverbs. They are typically used on buses and multiple instruments will be sent to these buses to save CPU.
Convolution reverbs work best in a Film and TV sound design scenario because they can transport what is being seen on screen into the same space.
For instance, a cave scene in a Film will need the correct reverb applied to make it look realistic. Because the actor’s dialogues are recorded either after the scene or in a way to remove the reverb, the reverb must be added in post-production to re-create the space.
In some TV and Film productions, Impulse Responses taken directly from that space can be used to recreate the atmosphere accurately.
Algorithmic reverb uses mathematical equations to create reverb artificially, while convolution reverb uses recordings to re-create real-life spaces. Convolution reverbs sound much better but are more CPU intensive and don’t have the endless possiblities that algorithmic reverbs provide.
How Does Digital Reverb Work?
Digital reverb falls into two categories:
- Algorithmic reverb
- Convolution reverb.
Both reverbs use feedback loops and delay lines to re-create/simulate a real, natural-sounding reverb space. You can control how a reverb sounds using size, decay, modulation, space, and more.
To show you how digital, algorithmic reverb works, we’ll quickly run you through the settings on Fab Filter’s Pro-R, what each does, and how it changes the sound.
Left Section – Distance, Reflections & Space
The left side of the plugin has 3 controls:
- Brightness – alters the decay of high frequencies for a brighter reverb sound
- Character – adds modulations to reverb to make it sound more characterful
- Distance – changes how close or far a sound is from the reverb source
These are all settings used to give the reverb a unique sound. They twist and change sounds in a way that makes us think the digital reverb is in-fact a real space.
Right Section – Decay, Stereo & Mix
The right side of the plugin has 3 controls:
- Decay – changes the size of the reverb, and time it continues for
- Stereo Width – changes the width of the reverb
- Mix – changes the amount of reverb applied using the plugin
Which Sounds Better? Digital or Analog?
The debate continues on…
Analog reverbs will generally provide a warmer, more characterful tone because of the imperfections. Digital reverbs will sound cleaner compared to, and if not used correctly, can sound extremely artificial. However from a cost and sound perspective, digital reverb takes the cake.
Analog reverbs refer to units like plate and spring reverbs that take up a huge amount of space. They take up this space because they use real springs (spring reverb) or metal plates (plate reverb), stretched across space, with multiple microphones to pick up the reverberations.
Natural reverb can also be captured using reverb rooms or chambers. These are physical rooms with extremely reflecting material inside, that have a speaker placed in the middle, with a microphone to capture the reverberated sound.
They will sound better, but as technology continues, digital will slowly out surpass reverb rooms and analog. This is largely because of its cheap, lightweight nature.
What About Reverb Pedals? How Do They Work?
Reverb pedals use a DSP to process the analog signal coming from the instrument, turn it into a digital signal and then convert that back to analog with the reverb on top. They work the same as digital reverbs, but are often plate or spring reverb sounds, which are inferior to many digital reverbs.
Because they are small, portable hardware units made for the purpose of traveling musicians for gigs etc. reverb pedals have far fewer controls than on a computer, but you generally get a few presets for hall, chamber and spring sounds
Digital reverb software can have as many controls as you like, whereas pedals usually only have a couple of controls.
You usually see pedals in live performance scenarios, but some producers use pedals and lo-fi hardware units for sound design and the imperfections, because they add character. Generally, it depends on what style you’re going for.
If you’re talking about a straight mixing and mastering scenario, digital reverb is a lot better and more suited to the task.
However, if you wanted the hiss and the imperfections for a sample pack or a creative sound design setting, it could be interesting to use pedals, tape machines and other devices to create weird and wonky sounds.
When To Use Algorithmic or Convolution Reverb
Algorithmic reverb is great for adding reverb to anything! You can use it on vocals, drums, synths, guitars etc. It excels at electronic sound design, because of the endless possibilities you can create.
They are best to use if you want to add multiple reverbs to a single track and not use a bus. This is because the CPU usage is low. If you did this with a convolution you’d quickly eat up your processing power.
Algorithmic reverbs are capable of huge variation and are capable of sounding completely realistic if dialed in correctly. They additionally have presets for analog reverbs which sound pretty accurate.
There are many emulations of plate and spring reverbs that sound almost indistinguishable from the real thing.
Make sure you get a good algorithmic reverb that’s trusted and respected by many music producers, because cheap digital reverbs can sound awful.
Convolution Reverb is good for TV and Film sound design. It also uses real-life space recordings, so is going to sound much cleaner and more realistic. We suggest using it for things like vocals, and other aspects like foley to transport them to the space seen on screen.
You can use a football stadium IR or a cave IR to transport any sound to that space, which makes matching a reverb for what is seen on screen very easy, because of the vast free downloads for impulse responses available online.
However, it’s very CPU intensive, so should be used sparingly and on buses in music production projects.
How Do They Sound?
What Is Acoustic Reverb?
What is Acoustic Reverb?
Acoustic reverb is the natural reverb you hear in the space you are in. If you clap in a cave, for instance, you will hear the reverb of the cave. The reverb is created from many sound reflections returning back to your ears at different times.
Because these sound reflections arrive at different times, it creates a space-y, echo-y sound that we know as reverb.
How Was Acoustic Reverb Re-created?
In older studios, it’s not uncommon to find reverb rooms. This was the first instance of re-creating acoustic reverb to add to instruments, vocals, and more.
Reverb chambers are rooms that have been specifically built with reflective surfaces, contain a microphone and a speaker, and use these to play the desired sound that reverb is needed on, record it and send it back through the mixing desk.
Before reverb rooms, instruments were recorded in the space that was wanted on the final recording. For instance, you’d record an orchestra in a huge orchestra hall to get all the beautiful acoustics and reverberations.
Although reverb rooms were a good solution to this, they were still expensive, and cumbersome and didn’t allow any controls to change the reverb.
This is where the plate and spring reverb came in – big units that used metal sheets, springs and microphones to re-create reverberation and add it to the signal. These had many more controls, were cheaper, but still very heavy, expensive and cumbersome.
That’s where digital reverb comes in…
Computer Scientists created software solutions to real-sounding reverbs using mathematical equations to re-create reverb digitally. This has become better with time, with reverb now sounding almost identical to the real thing. However, before, they sounded artificial. Cheaper digital reverbs will still sound artificial.
Since it’s invention digital reverb has allowed reverb to become completely accessible to anyone with a computer, and a DAW. It has drastically reduced the cost of reverb to an affordable price and sounds great.
With reverb rooms, you only had a few options available to you – hall and chamber sounds. This created a huge lack of creativity, and introduced the need for a mechanical solution, which then introduced the need for a digital solution.
Analog Reverb? Is There Such A Thing?!
Pretty much all reverb is digital. However, analog reverb does exist. You would categorize some guitar amp reverbs or pedals as analog, including big plate or spring reverb units found in studios.
Some pedals use DSP’s to process signals, these would be considered digital reverbs and are generally less favoured by guitarists because many like the analog imperfections that come with analog units.
Analog reverb could also be categorized as a reverb chamber, that uses microphones to capture the reflections of a vocal or whatever instrument is being played.
Many digital reverbs have presets that are capable of re-creating analog reverb styles. For instance convolution reverbs can literally re-create any real space, and even offer the ability to alter the size, decay and more.
Types of Analog Reverb
Spring reverb units use springs stretched across a unit, with speakers inside that play the sound, vibrate the springs, and then pickups that record the reverberation. They generally apply a metallic-sounding tone to reverb that is wonky and dissonant. They are fantastic for lo-fi sound design.
Plates use similar techniques to re-create reverb. They use large metal sheets, which are vibrated by speakers in the unit. These vibrations are then recorded by pickups inside the unit, which translate the reverb to the sound.
They are much more costly than spring reverbs, but sound much cleaner, and much better than their spring counterparts.
Plate reverbs are known for their luscious tones and are commonly used on vocal takes to give a wide, clear, and bright sound.
Plate reverbs are no longer really needed in the audio world, because algorithmic reverbs can accurately emulate them, and impulse response units even model some real-life plate reverb units. However, some claim they still sound better.
This is up for debate.
You can get some guitar pedals that create authentic spring reverb using springs and microphones. You can additionally get amps that do this too. Many guitarists tend to prefer the sound that comes from these units.
George Bell Edwards (IdleGod): Multi-Instrumentalist, Producer and Songwriter