Time Alignment

Time alignment is essential in any system with multiple speaker positions: left/right mains, delay towers, front fills, under-balcony speakers, stage monitors, and subwoofers. Without alignment, the time offsets between speakers create comb filtering, crossover cancellation, and confused spatial perception. The fundamental principle is simple: measure the arrival time from each speaker to the target position, then add electronic delay to the closer speakers so all arrivals are synchronized. The propagation delay is d/c, where d is the speaker-to-listener distance and c is the speed of sound (approximately 343 m/s at 20°C). Delay towers illustrate the concept clearly. A delay tower 30 meters from the main speakers needs approximately 87 ms of delay so its output arrives simultaneously with the main speakers. In practice, 5-15 ms of additional delay beyond exact synchronization is added so the mains arrive first, preserving the precedence effect (listeners perceive the sound as coming from the stage rather than the delay tower). For driver-to-driver alignment within a single speaker, the goal is to synchronize arrivals at the crossover frequency. The tweeter is typically closer to the listener than the woofer (because the woofer acoustic center is deeper in the cabinet), so delay is added to the tweeter signal. In modern DSP-equipped speakers, this alignment is done at the factory. In bi-amped systems with external DSP, the engineer must measure and align. Temperature affects alignment: a 10°C temperature change shifts the speed of sound by about 6 m/s, which at 30 meters translates to approximately 1.5 ms. For subwoofer alignment at 100 Hz, this equals 54° of phase shift — enough to reduce the summed level by 2 dB. Outdoor festivals should re-verify alignment between soundcheck and show time. SonaVyx measures arrival times from the impulse response and displays the delay offset between reference and measurement channels.