Algorithmic vs Convolution Reverb

1. Compare and contrast an algorithmic and convolution
reverb.
Demonstrate the difference and the important features in
both types of reverb.

2. Objectives
To compare and contrast an algorithmic and
convolution reverb.
To provide you with an understanding of the
differences and important features of both types of
reverb.
My name is Subrina. I decided to teach this because as I was listening
to the video lecture on convolution, the word “space” kept coming
back to me and I recall my own dance lessons and I often tell students,
when you choreograph you want to listen to the space in the music
and it is within these spaces, you come up with yet another dance
move. So I felt that by teaching this, I will somehow obtain a brand
new understanding of space in the context of composing music.
Please enjoy the presentation and thank you for reading.

3. Reverb
Before we try to understand algorithmic and
convolution reverb, let us explore reverb. What
is reverb?
Answer: Reverberation, or reverb for short,
refers to the way sound waves reflect off various
surfaces before reaching the listener's ear.

4. Reverb Explained
The diagram on the left shows one
person (the sound source) speaking
to another person in a small room.
Although the sound is projected
most strongly toward the listener,
sound waves also project in other
directions and bounce off the walls
before reaching the listener. Sound
waves can bounce backwards and
forwards many times before they
die out.
When sound waves reflect off walls, 2
things will happen:-
1. They take longer to reach the listener.
2. They lose energy (get quieter) with
every bounce.

5. Reverb Explained:-
 The listener hears the initial sound directly from the source followed by
the reflected waves. The reflections are essentially a series of very fast
echoes, although to be accurate, the term "echo" usually means a distinct
and separate delayed sound. The echoes in reverberation are merged
together so that the listener interprets reverb as a single effect.
 In most rooms the reflected waves will scatter and be absorbed very
quickly. People are seldom consciously aware of reverb, but
subconsciously we all know the difference between "inside sound" and
"outside sound". Outside locations, of course, have no walls and virtually
no reverb unless you happen to be close to reflective surfaces.
 Some rooms result in more reverb than others. The obvious example is a
hall with large, smooth reflective walls. When the hall is empty, reverb is
most pronounced. When the hall is full of people, they absorb a lot of
sound waves so reverb is reduced.

6. Reverb, is it necessary?
Now that we have a better understanding of
what reverb means, the next question to ask
ourselves is, why do we use reverb?

7. Why do we use Reverb?
 Reverb is most commonly used to put
elements of your song in a particular space
like a small room or hall etc.
 Reverb can also be used to add depth to
certain elements in your mix, essentially
making some elements sound further away,
while the other elements with less or no
reverb will be perceived as more upfront in
the mix.

8. Why do we use Reverb?
 Reverb can also be used as a creative effect or
sound design tool. An example; setting up a hall verb
on a return track (or parallel chain) set the dry/wet
amount to 100% wet and place a sidechain
compressor or gate after the reverb. Side-chain the
verb to the sound you are sending the reverb to
(usually on lead synths or vocals) that way every time
the sound is played the reverb closes or decreases in
level, and when the sound stops playing, the reverb
opens up.

9. Why do we use Reverb?
 Reverb can also be used a tool for making
pads. This means, you can take any sound
that sounds boring, run it through a big hall
reverb, with 90-100% wet with a long decay
time and, the end result; a pad sound!

10. Algorithmic or Convolution
 If you decide that you do not want to record
your song in a reverberated space, then you
will need to utilize your DAW and decide what
type of reverb is suitable for your mix.
 Your main choices:
 Algorithmic
 Convolution

11. Algorithmic vs Convolution
 Algorithmic reverb creates a sense of space
with a formula (like a digital synthesizer
creates sound with a formula, an algorithmic
reverb creates a sense of space with a
formula). This simulating the impulse
response that is applied to the sound signal to
create the reverb effect on that sound signal

12. Algorithmic vs Convolution
 Convolution reverb is taken from real rooms
using multiple microphones to capture or
‘sample’ the acoustics of a room, capturing
the complexities of real space. Then the sound
you make is filtered through ‘impulse
response’ generator to create an effect as if
your sound was recorded in that room.

13. Algorithmic vs Convolution
• Convolution reverb is more
like a sampler, used from
recorded sound.
• Algorithmic is more like a
digital synthesizer, creating the
effects of space through formula.
Point to note: Convolution can sound more ‘real’ capturing the complexities of
acoustics in a way that algorithm can’t quite generate.
• With algorithmic reverb, the
algorithms are adding the
reverb, so adjustments to the
parameters can be made.
• Impulse response file of a
convolution reverb, as it is
sampled from a room, tends
not to be as flexible.
• More complex• More control
• The convolution reverb can be
useful when wanting to add more
realness to software instruments (i.e.
instruments that aren’t samples and
have some natural noise)
• Algorithmic reverb can be
used on natural samples to
create interesting effects

14. Which one should you use?
CPU power, how much do you want to use?
• Algorithmic reverb : requires lesser CPU power
• Convolution reverb: needs a lot of CPU power
Other than CPU power usage, what else should
you consider?

15. Which one should you use?
USE BOTH and consider the following when choosing:
 Use convolution reverb on solo instruments because they help fill out the
sound where there aren’t many other things going on in your track. Your
mileage may vary, but that’s my general approach.
 The more instruments you have the more you can get away with a strictly
algorithmic reverb.
 Use convolution reverb on instruments that aren’t sampled. Sampled
instruments, even if sampled in a very dry environment, can often have a
small amount of natural room in the sample. When you mix this with an
algorithmic reverb, it can sound amazing.
 Algorithmic reverbs on the other hand tend to excel at adding reverb to
full mixes, or samples that already have some room recorded in.

16. Thank you for taking the time to read, I hope
you have found the information shared helpful.
It has certainly exposed me to aspects of
algorithmic and convolution reverbs I had never
known previously.