0 to 100%
Controls the initial echo density of the reverb. Low or moderate settings of Diffusion can result in an immediate and clear sound, with distinct reflections if Size (SIZ) is large (and therefore with lower density). This is preferable when you want clearer and more natural vocals, mixes and piano music. Higher settings of Diffusion will enhance the sound of percussion or other sounds with sharp transients.
This parameter affects both reverberation and early reflections.