How to Time-Align Speakers
Quick Answer
Time-aligning speakers means adjusting electronic delay so that sound from multiple loudspeaker sources arrives at the listener position simultaneously or in a controlled sequence. Proper alignment ensures coherent summation at crossover frequencies, eliminates comb filtering between overlapping sources, and maintains localization toward the primary system.
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Equipment Needed
- ✓Measurement microphone
- ✓SonaVyx Transfer Function or IR measurement tool
- ✓System processor with per-channel delay
- ✓Audio interface for dual-channel measurement
- ✓Mic stand at ear height
Step-by-Step Guide
Identify Speaker Groups
Map all speaker components that require alignment: main left and right arrays, subwoofers, front fills, delay speakers, under-balcony fills, and surround speakers. Each group operates as a separate source with its own propagation delay to the listener. The primary system (usually the main array) serves as the timing reference. All other sources are delayed to arrive at their respective coverage boundaries at the same time as, or slightly after, the main system.
Measure Propagation Delays
In SonaVyx's Transfer Function or IR mode, measure the impulse response of each speaker group individually while muting all others. The delay finder identifies the propagation time from the speaker to the microphone by detecting the first significant peak in the impulse response. Record this value for each source. Place the microphone at the coverage boundary where two sources overlap, which is where alignment matters most.
Calculate Required Delays
For each secondary source, calculate the required electronic delay as: delay = (main system propagation time) minus (secondary source propagation time). If the main system arrives at 50 ms and the fill speaker arrives at 20 ms at the overlap point, the fill needs 30 ms of delay. For delay towers, add 5 to 15 ms of additional delay beyond acoustic alignment to invoke the Haas effect, keeping the perceived image anchored to the main system.
Apply Delays to System Processor
Enter the calculated delay values into the system processor or DSP. Many processors display delay in milliseconds and optionally in feet or meters (at standard temperature, sound travels approximately 1 foot per millisecond or 343 meters per second at 20 degrees Celsius). Double-check that you are adding delay to the correct output channel. Applying delay to the wrong channel reverses the correction and makes alignment worse.
Verify Alignment with Combined Measurement
Unmute both the main system and the secondary source. Measure the combined transfer function at the overlap position. Well-aligned sources show smooth summation through the crossover frequency range with less than 3 dB of ripple. Misalignment appears as comb filtering, a regular pattern of peaks and dips. If comb filtering persists, adjust the delay in 0.1 ms increments until the combined response is smoothest. SonaVyx's before/after comparison can overlay the aligned and unaligned measurements.
Check Multiple Positions
Move the microphone to several positions within the overlap zone and verify that alignment is acceptable across the area, not just at one point. Perfect alignment at every seat is physically impossible when sources are at different distances, but the goal is to minimize destructive interference in the primary listening areas. Store traces from each position in SonaVyx for documentation and future reference.
The Physics of Speaker Alignment
When two speakers reproduce the same signal, they create an interference pattern that depends on the relative arrival time and level at each frequency. At frequencies where the time difference equals a half wavelength (or odd multiples thereof), destructive cancellation occurs. At frequencies where the difference equals a full wavelength, constructive reinforcement occurs. This creates comb filtering, a repeating pattern of peaks and dips with spacing inversely proportional to the time offset.
Subwoofer Alignment
Subwoofer alignment deserves special attention because low-frequency wavelengths are long (17 meters at 20 Hz), meaning even small time offsets produce noticeable phase effects. The crossover region between subwoofers and main speakers (typically 60 to 120 Hz) is particularly sensitive. Both time alignment and polarity must be correct for smooth summation. Some systems benefit from inverting subwoofer polarity and adding half a wavelength of delay at the crossover frequency to achieve in-phase summation.
The Haas Effect in Delay Design
The Haas effect (precedence effect) states that when two identical sounds arrive within approximately 35 milliseconds, the brain perceives a single fused image localized toward the earlier arrival. Delay speakers exploit this by adding extra delay beyond acoustic alignment so the reinforced sound arrives after the direct sound from the stage. This maintains natural localization while providing level support for distant listeners. The typical Haas offset is 10 to 20 ms.
Common Mistakes to Avoid
Aligning speakers by physical distance calculation alone without verifying with measurement, ignoring processing latency and driver offset
Setting delay fills to zero delay, which causes the fill to arrive before the main system and pulls the image toward the fill
Aligning subwoofers at the mix position rather than at the crossover coverage boundary where mains and subs overlap
Forgetting that sound speed varies with temperature (approximately 0.6 m/s per degree Celsius), affecting outdoor alignment
Using too much Haas delay on fills, which creates an audible echo rather than transparent reinforcement
Applicable Standards
| Standard | Clause | Relevance |
|---|---|---|
| AES-2id:2023 | Clause 5.3 | Impulse response measurement for delay identification |
| IEC 60268-5 | Clause 14 | Reference axis and acoustic center definition for loudspeakers |
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