The 5 key reverb plugin parameters (pre delay, diffusion, decay etc.)

The 5 key reverb plugin parameters (pre delay, diffusion, decay etc.) Reverb plugin parameters can differ greatly between different plugins, but there are 5 parameters which most reverb plugins share in common. These 5 parameters allow you to control the main elements of your reverb. In this article, we’ll examine these 5 reverb plugin parameters, what they do and how to use them.

How reverb works

First of all, when applying reverb in your mixes, it helps to understand how reverb occurs naturally…

When an instrument makes a sound, its sound propagates outwards sending sound waves in all directions. The first sound that a listener hears is the ‘direct sound‘. This is sound which travels directly from the instrument to the listener’s ears and so does not form part of the reverb.

Next to arrive to the listener is the sound that has reflected from one or two of the room’s boundaries. Room boundaries include the walls, ceiling and floor. We call these the ‘early reflections‘.

Next to arrive to the listener is the ‘reverberant sound‘. The reverberant sound is a dense collection of reflections which have reflected between many surfaces. There are so many reflections that we perceive a single sound which builds up and then decays.

The parameters on your reverb plugin give you control over these elements. This allows you to create the kind of reverb that you want to hear in your mix.

So, let’s look at the 5 reverb plugin parameters:

Reverb plugin parameters: Pre Delay

The first reverb plugin parameter that we will look at is ‘pre delay’. Pre delay controls the amount of time between the direct sound and the occurrence of the reverb. Changing the amount of time between the direct sound and the onset of the reflections can be used to control a number of things:

Pre delay and size

Shorter pre delay times give the impression of a smaller space. This is because it appears as though the sound does not need to travel as far to reach the nearest wall, ceiling, or floor to reflect from before it arrives to the listener. In turn, greater pre delay times give the impression of a larger space. That’s because it appears as though the sound is having to travel further to reach the nearest boundary to reflect off.

Pre delay and depth

As well as using pre delay to define the size of a space, you can also use pre delay to control the depth of an instrument. No pre delay makes it appear as though an instrument is further away from us. That’s because both the direct sound and the reflections will arrive to us at a similar time. This is what would happen if we stood in a room and we were far away from the instrument being played.

However, by introducing pre delay, the reflections arrive to us after the direct sound. This makes the sound appear closer to us. That’s because this is what you would experience if you were stood close to an instrument. You would first hear the direct sound straight from the instrument to your ears. After that, you would hear the sound that had reflected from the room’s boundaries.

This technique is often used for vocals. Generally, we want to keep the vocals up front in a mix, but with no pre delay, reverb makes the vocals sound further away. Introducing pre delay for the vocal reverb allows us to enjoy the benefits that adding reverb to the vocals provides, whilst keeping the vocals up front.

Pre delay for clarity

Pre delay can also be used to maintain a signal’s clarity when adding reverb to it. That’s because, by its very nature, reverb has the potential to make things sound less clear and less defined. As such, allowing the reverb to occur too quickly in relation to the dry sound can potentially compromise the clarity and presence of the signal. By using the pre delay parameter, you are able to delay the occurrence of the reflections. This retains the clarity and definition of the dry signal.

Reverb plugin parameters: Decay Time

The next reverb plugin parameter that we will look at is ‘decay time’. Decay time represents the time it takes for the reverb to fade away to silence. You may sometimes see decay time labelled on your plugin as ‘reverb time’, ‘reverb tail’ or ‘RT60’. Longer decay times will give the impression of a larger space, or of one which contains more reflective materials like brick or concrete. Shorter decay times will give the impression of a smaller space, or one which contains more absorbent surfaces such as carpet or fabric.

In practical terms, longer decay times can create a greater sense of ambience whilst shorter decay times are tighter and more controlled. When dialing in the length of the decay, it is important to ensure that your decay time is not so long that it causes the mix to lack clarity or feel washed out.

Reverb plugin parameters: Diffusion

Another key reverb plugin parameter is ‘diffusion’. The diffusion parameter on your reverb plugin controls both the dispersion and the density of the reflections. With high levels of diffusion, reverb sounds thick and smooth. With low levels of diffusion, reverb sounds thinner, sometimes to the extent that discrete echos can be heard.

Lowering the diffusion can help to prevent the reverb from overpowering the mix and making it sound washed out. However, lowering the diffusion too much can cause the reverb to sound metallic and chattery. As with most elements of mixing, finding the right balance is essential. Generally speaking, lower diffusion settings are better suited to things like vocals or strings as this helps to prevent things sounding washed out when applied to these sustained sounds. Meanwhile, drums and other percussive sounds benefit from higher diffusion settings. Higher settings make percussive sounds come across as big and beefy, whereas lower settings could potentially make them sound metallic and thin.

It’s worth noting that some plugins will allow you to control the dispersion and the density of the reflections separately. In this instance, the diffusion parameter would normally control the dispersion of the reflections only, and a separate density parameter would control the density of the reflections.

Reverb plugin parameters: Dampening

On your reverb plugin, the ‘dampening’ parameter is used to control the absorption of the reverbs’ high frequencies. It does this by controlling the reverbs’ frequency content over time. High values will create more high frequency absorption. This creates a reverb which sounds darker as the high frequencies are attenuated quicker. Lower dampening values create less high frequency absorption. This creates a reverb which sounds brighter as the high frequencies are attenuated more gradually.

Some reverb plugins will offer you both a high frequency (HF) dampening parameter which works in the way that is described above, and a separate low frequency (LF) dampening parameter to control the way the reverbs’ low frequencies decay. If only one dampening parameter is present, it will almost always be there to dampen the high frequencies.

Often, a reverb plugin will have other EQ filters available such as a pass filter. This could be in addition to, instead of, or as well as dampening controls. These can be really useful for equalizing your reverb, but keep in mind that these EQ filters do not affect frequency over time in the way that dampening does.

Reverb plugin parameters: Wet/Dry

Finally, a simple but important reverb plugin parameter to be aware of is the ‘wet/dry’ control. The wet/dry parameter allows you to control how much of the dry signal is mixed with the wet signal. If you are inserting your reverb plugin as an insert directly onto a track, then you use the wet/dry parameter to define the blend between the dry signal and the amount of reverb that you want.

If you are adding your reverb plugin to an auxiliary track, then things are a bit different. In this case, you will need to set the wet/dry parameter to 100% wet. That way, the auxiliary reverb channel will be 100% reverb. You can then send tracks to it using an auxiliary send.

As you can see, taking control of these 5 reverb plugin parameters gives you a great amount of control over the way that your reverb sounds. How do you like reverb to sound in your mixes? Leave a comment below.


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