Speaker Delay and Time Alignment: Getting It Right

When sound from two speakers arrives at a listener at different times, the signals combine with frequency-dependent phase differences. At frequencies where the time offset equals half the wavelength, the signals cancel (destructive interference). At frequencies where the offset equals a full wavelength, they reinforce. This creates a comb filter pattern of alternating peaks and nulls that severely colors the sound.

A 1-millisecond time offset creates a null at 500 Hz, a peak at 1 kHz, a null at 1.5 kHz, and so on. The result sounds hollow, thin, and phasey. Time alignment eliminates this comb filtering by ensuring both speakers' signals arrive simultaneously at the listening position.

Open SonaVyx transfer function mode. The delay finder automatically identifies the propagation delay between the reference signal and the measured microphone signal. Position the microphone at the primary listening position and measure with each speaker individually.

The delay finder reports the time in milliseconds from the reference to the first arrival of sound. The difference between two speakers' delays tells you how much alignment delay to add. Add delay to the speaker with the shorter propagation time (the closer speaker) so it matches the more distant one.

In a multi-zone system (mains plus delay speakers plus fills), alignment follows a hierarchy. First, align all components of the main system (left, right, sub, fill) to arrive simultaneously at the primary listening position. Second, align each delay zone to the main system at the point where the delay speaker's coverage begins.

Delay speakers should be set so their sound arrives 5-15 milliseconds after the main speakers' sound at the nearest listener to the delay. This exploits the Haas (precedence) effect, which causes the listener to localize the sound source at the main speakers even though the delay speaker is closer. Without this offset, listeners near delay speakers perceive the sound coming from behind them.

Subwoofer alignment is particularly critical because the crossover frequency region (typically 60-120 Hz) has wavelengths of 3-6 meters. A sub that is 1.5 meters closer than the mains creates a half-wavelength offset at 115 Hz, causing cancellation at the crossover frequency. This manifests as a "hole" in the frequency response where the subs and mains should overlap.

Measure the impulse response with subs only, then mains only. Compare the arrival times and add delay to whichever arrives first. Verify by measuring the combined response through the crossover region. A properly aligned system shows smooth summation without a dip at crossover. Check phase alignment at the crossover frequency using the SonaVyx phase display.

The speed of sound varies with temperature, and in outdoor events, the temperature difference between soundcheck and showtime can be significant. At 15 degrees Celsius, sound travels at 340 meters per second. At 35 degrees, it travels at 352 meters per second. For a delay speaker 30 meters from the mains, this temperature change shifts the alignment by 1 millisecond, enough to cause audible comb filtering at mid-frequencies.

For critical outdoor events, re-check delay alignment as the temperature changes. Humidity and wind also affect sound propagation, though their effects are secondary to temperature for most practical situations. SonaVyx delay finder shows the actual acoustic delay in real time, making it easy to verify and adjust as conditions change.