Allpassphase [top] 100%

While the magnitude remains unchanged, the phase response does not. An allpass filter introduces a frequency-dependent time delay. This delay causes a phase shift that varies across the frequency spectrum.

In professional mixing, all-pass filters are used to align multiple microphones. For example, if a snare top and bottom mic are slightly out of phase, a tool like Airwindows PhaseNudge can "rotate" the phase of one track to make them punch together perfectly. 4. Diffusion in Reverb

[ H(z) = \fraca_2 + a_1 z^-1 + z^-21 + a_1 z^-1 + a_2 z^-2 ]

The phase response of a filter describes how the filter affects the phase of the input signal. In an ideal world, a filter would not alter the phase of the signal, but in reality, all filters introduce some phase shift. The phase shift varies with frequency and can cause problems in many applications, such as audio processing, telecommunications, and control systems.