The Complete Guide to System Alignment: Delay, Level, and Phase

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TL;DR

System alignment follows a strict four-step sequence: polarity → delay → level → EQ. Changing the order wastes time because later steps depend on earlier ones. Step 1: verify polarity of every component using cross-correlation (positive peak = correct). Step 2: measure propagation delay from impulse response peak for each speaker and set electronic delay so all arrivals coincide at the target listening position. Step 3: match levels within ±1 dB using broadband pink noise. Step 4: apply corrective EQ only where coherence exceeds 0.6 — broad corrections from transfer function, not narrow notches. A properly aligned system gains 3-6 dB of headroom before feedback and dramatically improves clarity across the venue.

Why Order Matters

System alignment is the process of making multiple loudspeaker components work together as a single coherent source. In any multi-speaker system — mains + subs, mains + delays, left + right, FOH + monitors — each component must arrive at the listener at the right time, at the right level, and with the right polarity.

The four steps must be performed in order because each depends on the previous:

  1. Polarity — determines whether the speaker adds or subtracts. Everything else is meaningless if a speaker is inverted.
  2. Delay — ensures all components arrive simultaneously. Level matching and EQ are unreliable when comb filtering from time misalignment corrupts the combined response.
  3. Level — balances the energy contribution of each component. EQ decisions made with incorrect levels will be wrong.
  4. EQ — corrects the combined system response. Only meaningful after time and level are correct.

Step 1: Polarity Verification

A speaker with inverted polarity (+/- swapped at any point in the signal chain) will cancel with adjacent speakers instead of summing. At the crossover frequency between a sub and main, polarity inversion creates a 30+ dB null that no amount of EQ can fix.

How to check: Measure the transfer function of each speaker individually. The impulse response (IFFT of the TF) should show a positive initial peak. A negative initial peak indicates inverted polarity. SonaVyx's problem detector includes an automatic polarity checker using cross-correlation sign.

Common polarity mistakes:

  • Pin 2/3 swap in an XLR cable
  • Inverted polarity switch on a crossover or processor
  • Speaker driver wired backwards during manufacturing or repair
  • Phase inversion applied accidentally in a DSP processor

Step 2: Delay Alignment

Sound travels at approximately 343 m/s at 20°C (1 ms per 34.3 cm). A speaker 10 meters away arrives 29.2 ms after a speaker 0 meters away. If both play simultaneously, the listener at 10 meters hears a comb filter with nulls every 34.2 Hz — destroying the low-frequency response.

Measuring Propagation Delay

Measure the impulse response of each speaker individually using the transfer function with the delay finder enabled. The position of the first significant peak in the IR is the propagation delay. SonaVyx reports this in milliseconds and equivalent distance.

Setting Electronic Delay

The rule: delay the closer speaker (or the one that arrives first) so that it arrives at the same time as the farther speaker at the target position.

For delay towers at a festival:

  • Main PA to FOH position: measure 45.2 ms
  • Delay tower 1 to FOH position: measure 12.1 ms
  • Set delay tower 1 electronic delay: 45.2 - 12.1 = 33.1 ms

In practice, many engineers add 5-15 ms extra delay to delay towers (beyond time-alignment) to maintain the "precedence effect" — the listener perceives the sound as coming from the main PA even though the delay tower is closer.

Step 3: Level Matching

With polarity correct and delays set, play broadband pink noise through each component individually and measure the SPL at the target listening position. Adjust amplifier gains until each component contributes within ±1 dB of the target level.

Level matching is critical at the crossover frequency between components:

  • Equal levels: +6 dB summation at crossover (perfect)
  • 3 dB mismatch: +4.8 dB summation (acceptable)
  • 6 dB mismatch: +3.5 dB summation (noticeable tonal shift)
  • 10 dB mismatch: the louder component dominates; the quieter one contributes only 0.4 dB

Use the SPL meter for level matching — A-weighted for speech/vocal systems, Z-weighted for full-range music systems.

Step 4: Corrective EQ

Only after alignment is the combined transfer function meaningful for EQ decisions. With all components playing simultaneously, measure the transfer function at 3-5 positions across the listening area.

The Coherence Rule

Only apply EQ where coherence γ² exceeds 0.6. Low coherence means the response at that frequency is dominated by room reflections or noise — EQ cannot fix what is not a system response problem.

Broad vs Narrow Corrections

System EQ should be broad: Q values between 0.5 and 2.0, corrections of ±3 to ±8 dB. Narrow notches (Q > 5) are only for feedback suppression, never for system tuning. The AI diagnostic engine recommends EQ parameters automatically based on the measurement.

The EQ for live sound guide covers the distinction between corrective system EQ and creative channel EQ in detail.

Verification

After alignment, use the before/after comparison to quantify improvement. Store a trace before alignment (press S in the workspace) and compare with the final result. Well-executed alignment typically shows:

  • Coherence improvement of 0.2-0.4 in the crossover region
  • Frequency response within ±3 dB across 100 Hz - 10 kHz
  • 3-6 dB improvement in gain before feedback
  • Phase alignment within ±45° at crossover frequencies

The Tune PA workflow guides you through this entire process step by step.

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Last updated: March 19, 2026