In inverted mode, unless the delay is very large, the bass response will be weak, since the first notch is at dc. This case usually sounds high-pass filtered relative to the ``in-phase'' case (). As the notch spacing grows very large ( shrinks), the amplitude response approaches that of a first-order difference , which approximates a differentiator . An ideal differentiator eliminates dc and provides a progressive high-frequency boost rising 6 dB per octave (specifically, the amplitude response is ).
Flanger Feedback Control
Flanger Depth Control