differences between algorithmic and convolution reverb and their important features

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Hi, I am Rasheeq Rayhan from Dhaka, Bangladesh. This lesson is for week 5 of Introduction To Music Production at Berklee College of Music. I will compare and contrast an algorithmic and convolution reverb as well as demonstrate the differences and the important features in both types of reverb. Let us get done with the basic idea. So, what is “reverb”? Reverb is short for “reverberation”, which is basically what happens when a sound is “bounced” within a space, creating echoes. It is created when sound is produced in an enclosed space causing a large number of echoes to build up and then slowly decay as the sound is absorbed by the walls and air. This is most noticeable when the sound source stops but the reflections continue, decreasing in amplitude, until they can no longer be heard. For example, when you speak in a church and you hear remnants of your voice decaying after the initial sound was made. Reverb is one kind of delay and a very important one. Aside from distortion no effect is probably more important to the electric guitar than reverb. From almost the instant that amplifiers were created, guitarists yearned to be able to duplicate the sound of their amps in a hall or large room.

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This lesson is for week 5 of "Introduction To Music Production" at Berklee College of Music. I will compare and contrast an algorithmic and convolution reverb as well as demonstrate the differences and the important features in both types of reverb.

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Page 1: Differences Between Algorithmic and Convolution Reverb and Their Important Features

Hi, I am Rasheeq Rayhan from Dhaka, Bangladesh. This lesson is for week 5 of

Introduction To Music Production at Berklee College of Music. I will compare and

contrast an algorithmic and convolution reverb as well as demonstrate the

differences and the important features in both types of reverb.

Let us get done with the basic idea. So, what is “reverb”? Reverb is short for

“reverberation”, which is basically what happens when a sound is “bounced” within a

space, creating echoes. It is created when sound is produced in an enclosed space

causing a large number of echoes to build up and then slowly decay as the sound is

absorbed by the walls and air. This is most noticeable when the sound source stops but

the reflections continue, decreasing in amplitude, until they can no longer be heard.

For example, when you speak in a church and you hear remnants of your voice

decaying after the initial sound was made.

Reverb is one kind of delay and a very important one. Aside from distortion no

effect is probably more important to the electric guitar than reverb. From almost the

instant that amplifiers were created, guitarists yearned to be able to duplicate the

sound of their amps in a hall or large room.

Page 2: Differences Between Algorithmic and Convolution Reverb and Their Important Features

Reverb is frequently used in modern music recording to create a sense of space,

warmth, “vibe”, and reduce harshness. Phil Spector is famous for using a great deal of

reverb on his “Wall of Sound” recordings. When there’s a lot of reverb on a recording,

we say the recording is “wet” while an unprocessed, clean signal is called “dry”. Early

reverb simulators incorporated springs or large metal plates. Most fine recording

studios had their own large rooms dedicated to providing reverb. A speaker and

microphone were placed in the room and the reverberated sound was recorded.

But with the advent of technological evolution, it is now

possible to “create” that reverb digitally inside the DAW (Digital

Audio Workstation) or with reverb-pedals. Digital processing now

excels at simulating natural reverberation using various signal

processing algorithms. Since reverberation is essentially caused

by a very large number of echoes, simple reverberation

algorithms use multiple feedback delay circuits to create a large,

decaying series of echoes. More advanced digital reverb

generators can simulate the time and frequency domain

responses of real rooms (based upon room dimensions, absorption and other

properties). Reverb is a complex plugin built from many, many delay blocks. But instead

of adjusting individual delay blocks, we adjust parameters designed to represent how

delays function in a real space.

Page 3: Differences Between Algorithmic and Convolution Reverb and Their Important Features

Based on the technology the reverb plugins use they are divided in two categories:

1. Algorithmic Reverb

2. Convolution Reverb

1. Algorithmic Reverb:

It is your standard reverb plug-in. Algorithmic reverb creates a reverb from a

formula like a synthesizer creates sound. It synthesizes a room’s characteristics by

creating algorithms that generate a particular number of reflections, subject them to

high-frequency damping, add pre-delay, simulate a particular room size. It is a

mathematical representation. Examples:

Ø Apple GoldVerb

Ø Variety of Sound EpicVerb

Page 4: Differences Between Algorithmic and Convolution Reverb and Their Important Features

Ø Eventide Blackhole

Ø Lexicon PCM Native Reverb

Page 5: Differences Between Algorithmic and Convolution Reverb and Their Important Features

2. Convolution Reverb:

Convolution reverb uses real sound samples, recorded from real rooms (or modified

but based on real recordings in some cases) known as “Impulse Responses”. It is kind of

like the samplers as opposed to synthesizers. It is a sampled “snapshot” of a room’s

decay characteristics by capturing the acoustics of a room using multiple microphones

and producing an IR file for you. The reverb plug-in then filters your sound through this

impulse response to generate a “believable organic tail” based on the characteristics of

a real room. Examples:

Ø Apple Space Designer

Ø AudioEase Altiverb

Page 6: Differences Between Algorithmic and Convolution Reverb and Their Important Features

Ø Native Instruments Reflektor

There are some important differences in these two technologies:

I. Algorithmic reverb generates reverb sound strictly based on parameters you

set in the DAW. It tries to generate the same thing as convolution reverb but

because it is simulating the impulse responses (as opposed to the

convolution case) it can tend to sound fake especially when isolated in a solo

instrument case. Unless you have a very good reverb plug-in, I recommend

not using algorithmic reverb on your solo instruments.

II. Since the effect process for convolution reverbs involves running filters over

your signal and mixing that with another signal, they often have a larger

impact on CPU, which is not the case for algorithmic reverbs.

So, which type of reverb should you use? Well, the short answer is, both!

Convolution reverb is more “literal,” while algorithmic reverb is more “impressionistic.”

Convolution reverb is more flexible in that you can load different impulses and obtain

entirely different sounds—even impulses of tunnels, or something like the body of an

acoustic bass. However, it’s less flexible in other ways because changing individual

parameters—decay time, damping, and so on—is difficult, or in some cases, impossible.

Algorithmic reverb limits you to the chosen algorithm, but you have far more flexibility

to edit the algorithm’s parameters.

Page 7: Differences Between Algorithmic and Convolution Reverb and Their Important Features

The choice of which reverb to use is invariably an artistic one. You need to

experiment and determine what “sense of space” you want to create. Do you want to

recreate the original recording environment? Then consider a convolution filter for

“realism”. Do you want to add “character” to sampled instruments? Then you might

want to go with the algorithmic reverb. Each type of reverb has its own sound quality,

and neither one is “wrong” unless it does not sound right in the context of your music.

Try different types of reverb, and it should be obvious which works best with your

recordings.

I hope you enjoyed the lesson as much as I enjoyed making it. If you have any

questions do not hesitate to discuss with me so we can learn together! Thank you for

critiquing. Also, if you want to know more about my music, please visit my YouTube

channel. J

http://www.youtube.com/user/FrenzyPhrenesis

Regards, Take Care and Happy Learning!

*Word count: 998