Space Designer Pre-Dly (Predelay) in Final Cut Pro
Predelay is the amount of time that elapses between the original signal and the initial early reflections of the reverberation.
For a room of any given size and shape, predelay determines the distance between the listener and the walls, ceiling, and floor. Space Designer allows you to adjust the Pre-Dly parameter beyond the range that would be considered natural.
In practice, an extremely short predelay tends to make it difficult to pinpoint the position of the signal source. It can also color the sound of the original signal. On the other hand, an excessively long predelay can be perceived as an unnatural echo. It can also divorce the original signal from its early reflections, leaving an audible gap between the original and reverb signals.
The ideal predelay setting for different sounds depends on the properties of—or more accurately, the envelope of—the original signal. Percussive signals generally require shorter predelays than signals where the attack fades in gradually, such as strings. A good rule of thumb is to use the longest predelay possible before unwanted side effects, such as an audible echo, begin materializing.
These guidelines are intended to help you design realistic-sounding spaces that are suitable for different signals. If you want to create unnatural sound stages or otherworldly reverbs and echoes, you can experiment with the Pre-Dly parameter.