Early reflections are the fast reflections that arrive off walls, floors, and ceilings immediately after the direct sound. They are heard before the dense reverb tail and have a large influence on the impression of where a sound source is located. Reverbs often let you adjust them under headings such as “Early Reflections” or “ER”.
Difference from the reverb tail
Early reflections are relatively few and can often be perceived individually, while the reverb tail is the component in which reflections have become dense and continuous. The amount and spacing of early reflections suggest how close the walls are, how hard they are, and where the source sits. Extending only the tail changes the sense of front-to-back depth differently.
Creating the character of a space
Strengthening the early reflections tends to make the outline of a small room appear around the dry sound. Weakening them brings out the relationship between the direct sound and the diffuse tail. On vocals and drums, check within the song whether overly strong early reflections complicate the definition of the sound.
Relationship to pre-delay
Pre-delay relates to the time from the dry sound to the first early reflection. When it is short the reflections overlap the dry sound immediately; when it is long you tend to sense the space appearing after the dry sound. Not just how much early reflection there is, but when it starts, affects the sense of distance and the clarity.
In convolution reverb
With convolution reverb, the characteristics of the early reflections are contained in the IR you load. Choosing an IR of a real space brings its wall reflections and sense of size along with it. Some IRs let you handle early reflections and tail separately, so you can balance realism against effect.
How to check
Shortening the reverb tail and then varying the amount of early reflections makes the change easier to hear. Do not judge by stereo width alone; check in mono that the dry sound does not become blurred. The basics of creating space are covered in the reverb article.
