Phase Alignment
Time-align speakers and subwoofers for coherent summation using delay, polarity, and all-pass filters
Why Phase Alignment?
When multiple speakers reproduce overlapping frequency ranges, their signals can interfere constructively or destructively depending on their relative timing. Phase alignment ensures all speakers arrive in-phase at the listening position, maximizing coherent addition and preventing cancellation.
This is critical for subwoofer-to-main transitions, multi-way crossover regions, and distributed speaker arrays where path length differences cause timing mismatches.
Alignment Tools
Delay
Add time delay to earlier-arriving speakers to align with more distant ones. Measured in milliseconds or distance (meters/feet).
Polarity
Invert the signal polarity (180° phase flip). Used when speakers are wired in reverse or when crossover phase requires it.
All-Pass Filter
Frequency-dependent phase rotation without changing magnitude. Used to align phase through crossover regions where simple delay is insufficient.
Alignment Workflow
Measure Individually
Capture transfer function for each speaker/sub independently at the alignment position.
Compare Phase
Overlay phase traces to see timing differences. Use coherence-blanked phase for clarity.
Apply Corrections
Add delay, polarity, or all-pass filters to align phase through the crossover region.
Verify Combined
Measure with all speakers playing to confirm coherent summation at crossover.
Subwoofer-to-Main Alignment
The most common alignment task. Subwoofers typically have longer processing delay and higher group delay from their crossover filters.
1. Measure main speaker alone at crossover region
2. Measure subwoofer alone at same position
3. Adjust sub delay until phase traces align at crossover
4. Check polarity — try both, keep whichever sums louder
Distributed System Delays
In distributed systems (delay towers, under-balcony fills), delay speakers must be timed to arrive just after the main system to maintain precedence.
1. Calculate distance difference (main to listener vs. delay to listener)
2. Convert to time: delay_ms = distance_m / 0.343
3. Add 5-15ms extra delay for Haas effect precedence
4. Fine-tune with phase alignment at crossover with main