Get More From Reverb: Early Reflections, Tail & Pre-delay Explained
Understand how the different parts of a reverb signal contribute to your sound, and how to use them in music production
We demand a lot from our reverbs — sometimes to recreate the realism of spaces like a million-dollar drum room or a vocal chamber, and other times to deliver imaginative, otherworldly effects.
But whatever the application, there’s usually multiple distinct parts to any given reverb signal, and you’ll have noted these parts in many of our reverb plugins. If you cast your eye over Renaissance Reverb (below) you can see the main parts of the reverb signal represented.
There are two clear components shown in orange within the graphical display:
- The spiky vertical ‘sticks’ are the reverb’s early reflections.
- The solid filled orange area represents the reverb’s tail.
- The gap on the left of the tail before it starts represents the pre-delay applied to this particular reverb patch.
In this article, we’re going to illuminate what each of these terms means, where it comes from in a real world reverb signal, and how to actually use it and make decisions about it in a mixing context. We’re going to need some good old-fashioned diagrams to get this right. Let’s jump in!
How Reverb Works in a Real Space
Imagine you’re standing in a room and a loud sound is triggered quite close to you. The sound energy starts to come radiating out from the source, spherically in every direction.
Direct Sound
The first thing that sound energy comes into contact with is you and your ears, while most goes past or around your head. In reverb terms, we call this the Direct Sound. It’s the first instance of the sound that’s traveled the shortest distance to arrive, whether it’s at your head or at a microphone.
Early Reflections
When sound travels outward, it eventually hits a boundary like a wall, ceiling, or floor. The first reflection from this surface is called an early reflection. These reflections arrive at our ears a few milliseconds after the direct sound, with each one following a slightly different path. Early reflections help us sense the size and shape of a space.
As you can see in H-Reverb, below, these early reflections come first, and they represent those first few reflections of the sound source off the walls of the room and directly into our ears (or microphone).
Pre-Delay
After the direct sound, you may notice a short delay before any reflections or the reverb tail (below) kick in. This can simulate the feel of a real space, but more often, pre-delay is used to create artificial distance between a sound and its reverb tail, adding space before the tail envelops the direct sound and early reflections. We’ll dive deeper into pre-delay a little later.
Reverb Tail
Finally, we embrace the chaos. While our early reflections bounced straight off a single wall then back to us, most reflections bounced onto other surfaces, which bounced onto other surfaces, which finally hit us all at once along with many other reflections that had built up into a soup of copies of the original sound. This is the diffuse reverb tail.
You know the diffuse tail of a reverb, actually – it’s the part you think of when you consider reverb, while the early reflection are harder to notice. To hear the difference, try solo-ing each using a plugin like H-Verb, RVerb, TrueVerb or the IR Series reverbs.
The reverb tail is the dense, diffuse wash of sound caused as hundreds, thousands or many more reflections overlap as they reach the listener or microphone, after bouncing around the space multiple times along with many others.
How to use Reverb Early Reflections in Mixing
Early reflections in a reverb signal play a couple of roles. They’re somewhat inaudible unless you know what you’re looking for, and so the role of the early reflections is often carried out subconsciously.
Early Reflections in reverb give our ears cues for two things: the size of the space we’re in (or that our sound source is in), and the source’s positioning within the space. If you suddenly turned off early reflections from the piano and snare reverb signals above, their positioning suddenly becomes a lot less obvious to us.
So while they’re not an overt part of any sound, early reflections give that ‘certain something’ to a sound that you miss when it disappears.
How to use the Reverb Tail when Mixing
Meanwhile, the reverb tail quietly handles much of the work without needing as much focus. This diffuse tail creates the unmistakable "reverby" quality of a reverb sound. While early reflections convey information about position and spatial dimensions, the reverb tail shapes our perception of the space’s character and size.
You probably don’t need to listen to an audio example to imagine the difference in sound between a large, cavernous church and a large, well-treated studio room and a large stadium. The reverb tails generated in these spaces do enough to describe them to our ears and hearing system.
RT-60
We often judge a reverb’s tail by how quickly it decays. In technical terms, we judge the length of a reverberant signal as the time it takes to reach 60dB below its initial impulse, using a measurement called RT-60 (Reverb Time to minus 60dB).
In a mixing context, keep in mind that the ‘Decay Time’ you’re setting might not be the absolute time taken for the reverb to fade to silence – if the RT-60 is used, the actual time may be longer than appears on a plugin’s UI.
How to use Reverb Pre-Delay when Mixing
How does this notable gap in the reverb signal, between the direct sound and the onset of reflections, work in hands-on contexts? Pre-Delay changes its function depending on the context it finds itself in.
Using Pre-Delay to Make Something Closer
On the one hand, pre-delay has a classic use on vocals. Dial up the pre-delay on your vocal reverb to put some space between the direct sound and its washy late reflections. The technique here is to make a vocal sound closer to the listener, as the pre-delay emphasizes the direct sound. In our real-life room, a sound being closer would put more time between hearing the first direct sound and hearing the follow-up early reflections.
Using Pre-Delay to Make Something Seem Further Away
Be mindful with pre-delay, as its effect varies depending on the context. While pop and rock producers often use pre-delay to bring sounds closer, orchestral producers apply it to create a sense of greater distance.
In orchestral mixing, where the virtual space is already expansive and the instruments are set far back, adding pre-delay enhances the perceived distance by increasing the gap before early reflections in that large space.
How to use Reverb Direct Sound when Mixing
Finally, even though our direct sound is arguably not part of the reverb, it does compare to it in relative terms. When the direct sound is turned up in level, the reverb is comparatively lowered. Whether this is done using gain controls or a dry/wet mix slider, the real-word implication of the balancing or rebalancing is that the reverb is perceived as more or less dominant compared to the dry sound.
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