Sub Delay & Phase Calculator
Calculate the delay needed to time-align a subwoofer with your main speakers and see the cancellation if you don't.
Inputs
Speed of sound: 343.4 m/s
Top view
How it works
Sound travels about 343 m/s (1 ms per 34.3 cm). If the subwoofer is farther from your ears than the main speakers, its sound arrives late; at the crossover frequency both speakers play the same note, and a timing mismatch makes them partially cancel.
Δt = |d_sub − d_main| / c phase = 360° · f_xover · Δt Sum level = 20·log₁₀ |cos(π·f·Δt)| (equal-level, same-polarity)
The graph shows the loss of summed output if you do nothing. At the frequency where the phase difference reaches 180° (f = 1/(2Δt)) the two sources cancel completely. Delay the closer source by Δt to line the wavefronts up again. Many AV receivers and DSPs have a “distance” setting that does exactly this; in a car head unit it’s called time alignment.
A pure delay isn’t the whole story: crossover filters, box tuning and room modes add their own phase shifts (the “phase” knob on a sub is a crude all-pass). The best approach is to apply the calculated delay, then fine-tune by ear or by measurement with the polarity (0°/180°) switch, choose the setting with the most bass at the crossover.