Phase Response

Every audio system — speakers, filters, rooms — imparts both magnitude and phase changes to signals passing through it. While magnitude response (the frequency response curve) gets most of the attention, phase response is equally important for transient reproduction and multi-speaker system coherence. A linear phase response means all frequencies experience the same time delay (constant group delay). An analog minimum-phase system has a phase response uniquely determined by its magnitude response via the Hilbert transform — you cannot change one without changing the other. FIR filters can achieve linear phase, but at the cost of added latency. In multi-speaker systems, phase alignment at the crossover frequency is critical. If a woofer and tweeter are 180° out of phase at the crossover point, they cancel rather than sum, creating a deep notch in the response. Adjusting delay, polarity, and crossover filter type to achieve phase alignment across drivers is one of the most impactful optimizations a sound engineer can make. Phase is measured using a dual-channel transfer function: the system under test is excited with a known signal (reference), and the output (measurement) is compared. The phase at each frequency is the angular difference between output and input. Phase is inherently ambiguous beyond ±180° (it "wraps"), so phase unwrapping algorithms are needed to reveal the true cumulative phase shift. Group delay — the negative derivative of phase with respect to frequency — is often more intuitive than raw phase. A constant group delay means linear phase; a varying group delay means different frequencies arrive at different times. Peaks in the group delay correspond to resonances in the system. SonaVyx displays wrapped and unwrapped phase alongside the magnitude plot in transfer function mode, with group delay computation.