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Reverb demystified - How Reverb Plugins work

Reverb plugins demystified

Reverb is an incredibly powerful tool for making an audio signal sound like it was recorded in a sonically pleasing acoustic environment or for creative sound design.

1) Choosing your reverb (Convolution vs Algorithmic Reverb)

Convolution Reverb

Convolution reverb takes a signal and processes it using an impulse response (IR) of a real acoustic space or hardware reverb.

Acoustic spaces are captured by recording an environment using a short, sharp sound. The initial sound is used to excite reflections from the environment and is removed later to leave just the response, a process called deconvolution.

The software convolves the impulse response sample and input signal together.

Pros

The advantage of convolution reverb is that it can accurately simulate acoustic spaces and can sound very natural.

Cons

The disadvantage of convolution reverb is that is it computationally complex which can take up a lot of a computer’s processing.

Limited controls compared to a lot of algorithmic reverbs.

Algorithmic Reverb

Any reverb that does not use convolution will fall into this category. Mathematical algorithms are used to simulate the delays that occur in reverb. Synthesis of echoes can be performed much for efficiently on a computer using less processing power.

Pros

Algorithmic reverbs often have more controls, flexibility and use less CPU. 

Cons

Algorithmic reverbs rarely sound as natural as convolution reverb.

2) Using a Reverb as a Send/return vs Inserts

Inserting reverb plugins directly on to audio tracks may be the quickest way to use reverb effects, but using a few sends and returns has many advantages.

-Being able to use to other effects on the reverbed signal such as EQ, gates and sidechain compression.

-Sending more than one channel to the same reverb return will make elements sound like they belong in the same acoustic space as well as saving CPU.

-Having a few reverb returns means that controlling the reverb levels over a whole mix can be done with few faders.

3) Common Reverb Types

Rooms

These are typically smaller in size than a hall and less noticeable than a chamber. They are great at creating a sense of space, without being overtly distinguishable.

Great for creating more subtle ambient effects on any instrument.

Hall

These are a similar environment to where you would expect to hear music performed live such as a concert hall.

These have longer reverb times and can be great for making signals sound further away and pushing them back in the mix.

Chamber

A reverberation chamber is a purpose built room that is designed to be very reverberant where the signal is played through one or more speakers and recorded with microphones to capture the acoustics of the room.

Great for creating an ambience more noticeable than a room, but smaller and denser than a hall. Works well on any instrument but especially popular on vocals.

Plate

These originate from purpose build mechanical hardware reverbs using a metal plate suspended on springs. A transducer converts the input signal into vibrations on the plate which are then captured using a contact microphone on the plate.

They have short reverb times and are known to work well with vocals and drums.

Spring Reverb

These originate from small, inexpensive units using a transducer to convert the input signal into a mechanical motion along a spring.

At the end of the spring, another transducer converts this back into an electrical signal. Some of the energy of the wave is reflected and stays in the spring, creating a unique reverb character to the sound.

These have a unique unnatural sound that is great for surrealism and popular with guitarists.

Gated reverb

A noise gate is used on reverb tail to rapidly cuts off secondary reflections.

The reverbed signal is sometimes compressed first to exaggerate the reverb tail before the gate.

Great for drums such as kick and snare.


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