Question 1

How do I use transfer function measurements to time-align speakers?

Accepted Answer

Time alignment ensures that sound from multiple speakers arrives at the listening position simultaneously. The process: measure the transfer function of each speaker individually (mute all others). Find the propagation delay for each speaker using the impulse response peak or the group delay at crossover. Set delays on the DSP so that the farther speakers are delayed to match the closest speaker. Verify by measuring the combined response and checking that the magnitude is smooth at the crossover frequency and the phase traces overlap. If two speakers are 3 meters apart in distance to the listener, the farther one needs 3/343 = 8.7 ms of delay. SonaVyx delay finder automatically detects the propagation delay from the impulse response.

Question 2

What is the workflow for aligning a main speaker with a subwoofer?

Accepted Answer

Main-sub alignment is critical around the crossover frequency (typically 80-120 Hz). Step 1: Set the crossover filter on the DSP processor. Step 2: Measure the transfer function of the main speaker alone, noting the phase at crossover. Step 3: Measure the sub alone, noting its phase at crossover. Step 4: Adjust the sub delay until its phase at crossover matches the main within ±30 degrees. Step 5: If polarity is inverted (180 degrees off), flip the sub polarity and readjust delay. Step 6: Measure both together and verify that the magnitude sums smoothly (no dip at crossover). The correct alignment shows a smooth magnitude transition and maximum level at crossover compared to either speaker alone. SonaVyx dual-trace overlay makes this easy to visualize.

Question 3

How do I align fill speakers with the main system?

Accepted Answer

Fill speakers (front fills, delays, under-balcony) must be time-aligned so that the audience perceives a single source. The Haas effect allows fills to be up to 20 ms late relative to the mains without being perceived as separate sources. For speech: align fills to arrive 5-10 ms after the mains at the overlap zone. For music: tighter alignment (0-5 ms) is preferred to avoid comb filtering. Measure the transfer function at the overlap zone between main coverage and fill coverage. Adjust fill delay until the impulse response shows a single coherent peak. Then adjust fill level to be 6-10 dB below the main level at the overlap zone. SonaVyx multi-trace overlay lets you compare the main-only, fill-only, and combined responses in one view.

Question 4

What is group delay and how does it relate to speaker alignment?

Accepted Answer

Group delay is the negative derivative of phase with respect to frequency: tau = -dPhi/dOmega. It represents the time delay experienced by a narrow band of frequencies passing through the system. For a perfect system with no frequency-dependent delay, group delay is flat (constant). Crossover filters, loudspeaker drivers, and room reflections all cause frequency-dependent group delay. At crossover frequencies, group delay typically shows a peak corresponding to the filter transition. For alignment purposes, match the group delay of two speakers at their crossover frequency. If the main shows 5 ms group delay at 100 Hz and the sub shows 12 ms, the sub needs 7 ms of additional delay (or the main needs -7 ms if the DSP supports it). SonaVyx displays group delay below the phase plot.

Question 5

How do I know if my speakers are correctly aligned after adjustment?

Accepted Answer

A correctly aligned multi-speaker system shows these characteristics in the combined transfer function: smooth magnitude through the crossover region without dips or peaks greater than ±3 dB, phase that transitions smoothly without discontinuities, coherence that remains high (above 0.8) through crossover, and the combined level at crossover is 3-6 dB higher than either speaker alone (depending on the summation type). If you see a deep null at crossover, the speakers are partially canceling due to phase mismatch. If you see a sharp peak, they may be summing constructively but with incorrect polarity. SonaVyx before/after comparison mode lets you store the individual speaker traces and compare them against the combined response to verify proper summation.

Question 6

What is the difference between acoustic alignment and electrical alignment?

Accepted Answer

Electrical alignment refers to the delay and filter settings applied in the DSP processor. Acoustic alignment is what actually happens at the listening position after sound travels through the air. The two differ because: speakers have inherent latency (the voice coil takes time to respond to the electrical signal), crossover filters introduce group delay, and physical distance adds propagation delay (approximately 2.9 ms per meter at 20 degrees Celsius). Electrical delay compensates for differences in propagation delay between speakers. But you must verify the result acoustically because speaker-to-speaker latency variations and room reflections mean the electrical settings do not always produce perfect acoustic alignment. Always measure at the listening position, not at the speakers. SonaVyx measures acoustic alignment directly.

Question 7

How accurate does my time alignment need to be?

Accepted Answer

The required accuracy depends on the frequency range of overlap between the speakers. At the crossover frequency, a phase error of 30 degrees corresponds to a time error of 1/(12 × frequency). At 100 Hz crossover (main/sub): 30 degrees = 0.83 ms = 28 cm. At 1 kHz crossover: 30 degrees = 0.083 ms = 2.8 cm. At 3 kHz crossover: 30 degrees = 0.028 ms = 0.95 cm. This means sub-main alignment can tolerate about 1 ms error, while high-frequency horn alignment needs sub-millisecond precision. Most DSP processors offer 0.02 ms (20 microsecond) delay resolution, which is sufficient for all crossover frequencies. SonaVyx delay finder resolution depends on sample rate: at 48 kHz, one sample = 0.021 ms = 7 mm in air.

Question 8

Can I use transfer function measurement to align a line array?

Accepted Answer

Yes, transfer function measurements are essential for line array optimization. The process differs from point-source alignment because line array elements share overlapping coverage by design. Key measurements: verify inter-element splay angles produce smooth vertical coverage by measuring at multiple vertical positions. Check that the array is physically straight (no twisted or sagging elements) by comparing magnitude responses at left and right positions. Align subwoofers to the main array at the crossover frequency using the same phase-matching technique. Measure horizontal coverage uniformity by walking the measurement mic across the audience area. For flown arrays, use the array calculator to predict delays, then verify with measurement. SonaVyx trace store function lets you capture and compare responses at multiple positions.

Speaker Time Alignment: Using Transfer Function Phase for Multi-Speaker Systems

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