You are here: Home page » Free Tutorials » About Reverbs

About Reverbs


Reverbs - hardware or software - are used to artificially simulate acoustics of rooms. To date, there are roughly 4 approaches to how this can be done:


Mechanical reverb devices
A)
You play the music to be heard through loudspeakers in a specially created reverberation room and record them with microphones again.
B) You play the music with transformers on plates or springs and picks up the vibrations at the other end again. This creates a kind of reverb.

Electronic reverb devices
C) Algorithms are created that simulate the decay of sound waves as naturally as possible. Today, some plug-ins can do this so well and cheaply that the entire mechanical Hall production hardly comes into play. = This sort of reverbs is called Algorithmic Reverbs
D)
You create an acoustic image of a desired room by playing back suitable measuring signals. These measurement signals are picked up and charged into a so-called "Impulse Response" (IR).
Special software "interweaves" these IRs into the music to be heard.
This sort of reverbs is called Convolution Reverbs


Reverb Parameters
Reverb-devices have some setting options to simulate as many different rooms as possible. The most important are explained here.
Most of the parameters are related to algorithmic reverbs.

See the next tabs...

Basically today's reverb plug-ins offer different reverberation rooms. For some, the parameter "Reverb-Type" is called "Room-Size".
Accordingly, settings are then called

- Small Rooms
- Chamber
- Hall
- Church
- Cathedra
- Plate / Spring
... and so on.


When working with orchestral samples, "Chamber" / "Hall" / "Church" are often a good choice. With this you select an algorithm that simulates concert halls as accurately as possible.

With a convolution reverb, the choice of space becomes a main theme first, because you can specifically select the sound of a particular room. The spaces of convolution reverb rarely sound neutral. To be honest, I do not like many rooms ... So it usually stays at 1-2, despite a wide choice.

This value sets when the entire reverb process should start. Imagine standing in the middle of a cathedral. If you clap your hands, it will be a while before the first reflection comes back from the walls (if you do not take the floor into account). So "Predelay" sets the time that passes from direct sound to the arrival of the first reflections.

2 Examples of simulation in a cathedral:
A) Your colleague is standing near you and claps his hands... A large pre-delay time must be set (25ms to 100ms). By the way: For 1m the sound needs 3ms.
B) Your colleague stands far away from you in the cathedral and claps his hands... The direct sound reaches you only a little earlier than the first reflections. A small predelay time must be set (0ms to 10ms).
So that means:

Small pre-delay times = far away sound source
Big pre-delay times = nearby sound source



direct signal - 1st reflections
larger time difference
direct signal - 1st reflections
smaler time difference
Without (less) Predelay
(sound source is far away)
With Predelay
(sound source is close)

The first reflections that reach our ear evaluates our brains to learn about the space and distance of the sound source.

These Early Reflections (ER) are the key to what we want to do with our reverb effect.

If we want to set an instrument far away from us - into the depth of the room, you need a reverb with early reflections that can solve this task.


Unfortunately, not all reverb plug-ins can solve the tasks described here equally well. Test your reverb collection ...



These Early Reflections do not create "a Depth". These Early Reflections create a "Depth" without a lot of Tail.

These Early Reflections create no Depth

Early Reflections create Depth

Reverberation actually consists of the direct signal, the early reflections, and finally, so many reflections come together that they all together form the actual reverb. One often calls this part "tail".
Time usually sets the total reverb time over all. So this parameter allows you to set how long it takes for the reverb to disappear (-60dB).
Because the ERs take only a short time, "time" can actually be equated with the tail - the release time of the sound.

Often associated with this is also a filter with which you can make the frequency more and more dull over the reverberation time. That sometimes means "Damp". Often there is also a controller with which one can adjust the space-complexity (number of corners, wall surfaces etc.). This regulator is often called "diffusion". See below...



This Tail does not push the signal "into Depth". This Tail does push the signal "into Depth".

Tail without Depth

Tail with Depth in the meantime

A reverb can sound dull, thin, bright. To simulate these sounds, reverbs often have filters that can directly affect the reverb signal. Some reverbs already have such filters on the input so that e.g. low-frequency signals certainly do not get into the effect.



Reverb Signal not Filtered. For the distance the signal sounds too brilliant and too much inflated in the low frequencies.

The Reverb Signal is filtered in the heights.
The signal sounds more natural now but still "blowed up" in the low frequency range.

At such extreme distances, the signal must be filtered with an EQ before the reverb effect so that the sound equals the distance. We see, the EQ has to work pretty well.

without any filter

with damped heights

with damped heights and a "pre" EQ

As already mentioned, convolution reverbs use so-called Impulse Responses from the right rooms. Because these are "static snapshots", algorithmic reverbs usually sound a bit more natural when they fade out. The strength of the IRs, however, is to create fairly natural, acoustic distances (depths). So if you only use the first part of the IR (0-400ms approx.) You get a nice room depth. With an algo-reverb you can add the tail - the reverb is perfect.

A) Look for IRs in your Convolution Reverb that will make the music sound far away at 100% wet.

The Early Reflections are in the first 300-400ms.
Only this we want to use now ...
B) If you have the option, shorten the IR to about 1.5s in total.
Now the area with the Early Reflections is larger in proportion and better to work.
C) If it is an upscale convolution reverb, you can now hide the IR signal after about 400ms (fade out).

This procedure makes it possible only to have the IR's early reflections.
Try it out.

Sound with complete IR

Sound with shortened IR (to ER)

Sound with ER and some Tail (from Algo-Reverb)

So it's always crucial what you want from a reverb.
A) Should it push instruments in different depths - but without Tail?
B) Should it bring a mix to shine with a beautiful tail ? ...But without depth again?
C) Should it add a reverb tail to a soloist without moving him to the back at the same time?

All that can reverbs do.
Not all can do it equally well.
That's why you have to get to know your own tools.
Check them out about ERs for depth / Tails without depth
Now you know a bit more what all the parameters are for.




Let's finish the theme of "Reverb" with music...
... of course played with samples and mixed with created depths and a tail ...
Bachs Violin Concerto BWV 1041 (excerpt), played with VSL-samples. The orchestra plays in a certain distance...

... and the the solo violin sounds closer to the listener (no ER only Tail) ...because it should sound as soloist.