Allpassphase Today

When recording a single source with two microphones (like a snare drum with a mic on top and bottom), the sound hits the microphones at slightly different times. This causes "phase cancellation," where certain frequencies disappear because the sound waves are fighting each other.

AllPassPhase: The Secret Weapon for Phase Dispersion In modern sound design and mixing, AllPassPhase allpassphase

The most famous use of allpass filters is in digital reverb. In 1962, Manfred Schroeder realized that a series of allpass filters could produce a high density of echoes without metallic coloration. Each allpass filter recirculates the signal, smearing transients into a smooth decay. Without allpassphase, reverb algorithms would sound like a sparse set of distinct echoes. With it, we get the lush, dense tails of a concert hall. When recording a single source with two microphones

The coefficient a is related to cutoff frequency fc and sample rate fs by: In 1962, Manfred Schroeder realized that a series