This article analyses the claim that reverb brightens sound because of the precedence effect.

The Precedence Effect

When a signal enters the ear, any sound occurring within about 50 ms (or some echo threshold) is perceived as a single event, with the spatial location being perceived as the location of the first sound. This effect is often used for binaural effects such as sound localization. For example, if a sound is heard in your left ear slightly before your right ear, it’ll sound like it’s coming from your left.

On Frequency Perception

So how does plate reverb brighten sound? According to the precedence effect, it has high frequencies, and those frequencies are perceived first. Therefore, reverb with zero pre-delay will be predictable and intelligible as one sound. I disagree with this in practice, though. Turning up a reverb without pre-delay doesn’t make the source sound louder. The reverb and source are still distinct. And the impulse still sounds first, directly, and then reverb takes over. Modern plate reverb, especially in digital form, treats reverb as a separate sound, with lengthy decays, pre-delay, and sidechain. This adds depth without losing the clarity of the original sound.

On Source Signals

As for reverb brightening the source? It seems like something that’s commonly repeated but rarely understood. The goal of applying reverb should never be to brighten the sound. This is a job for EQ, not reverb. The reverb itself has tone and the reverb itself may be bright, but this still doesn’t change the source, no matter how it’s mixed. The precedence effect ends up confusing and vague in its explanation of this effect, because it implies more or less that reverb and source are the same sound, and that the introduction of high frequencies changes the tone of the source signal. I’ve seen a few people claim that “reverberated highs” are perceived before the source signal, which makes no sense.

On Reverb Use

Reverb historically has been used to define space. Reverb nowadays is often used as its own sound. If you are using reverb to change the tone of your source audio, you are using reverb as something it isn’t. Sure, you could throw a short plate onto a vocal for “tone”, but it’s not going to be as obvious as something like “brightening”, at least not as predicted by the precedence effect. So the precedence effect is an interesting angle to analyse the effects of plate reverb from, but it seems too theoretical and runs counter to a lot of my practical experience. Specifically the use of pre-delay to improve clarity and, in fact, make the sound brighter! Under the assumptions of the precedence effect, this would be an impossibility.

So while the precedence effect is important and does legitimately explain many things, I don’t find it particularly applicable to plate reverb.