The delay times for playback heads 2, 3 and 4 are 2x, 3x and 4x the delay time of playback head 1 respectively. When you use tap input, this is set as the delay time (tap delay time) for playback head 1, which is the base delay time for each mode.
Modes 8–12 feature the sound of playback head 4, which was not on the Roland Space Echo RE-201.
MODE 12 differs from the other modes, in that the positions of the four playback heads are optimized to create a highly dense sound.