Field Story

Subwoofer Phase War at the Amphitheater

An outdoor amphitheater deployed four subwoofers in a line array, but seats in rows 12-18 heard almost no bass below 120 Hz. Transfer function measurement revealed a 22 dB null at the crossover frequency caused by phase cancellation between the main tops and subs. Correcting the sub delay by 4.2 ms and flipping polarity on the outer pair restored flat response across all seats.

Outdoor Amphitheater

Polarity Checker per AES-2id

TL;DR

Polarity verification is a critical early step in AES-2id system alignment. An inverted polarity speaker causes destructive interference with adjacent speakers, creating a deep null at the crossover frequency that no amount of EQ can fix. The polarity checker uses cross-correlation analysis to determine whether the impulse response shows a positive or negative first arrival, indicating normal or inverted polarity respectively. SonaVyx problem detector includes polarity checking that works in real time during your alignment session, catching wiring errors and processor polarity inversions before you spend time on detailed tuning.

Polarity in System Alignment

Every speaker in a multi-way or multi-source system must have correct polarity for constructive summation. A single inverted driver or cable causes a 6 dB null at the crossover frequency.

Sources of Polarity Errors

  • Swapped wires at the speaker terminal or amplifier output
  • Polarity inversion in a DSP crossover or processor
  • Mismatched polarity between left and right channels
  • Multiple polarity inversions that cancel out in some paths but not others

Detection Method

  1. The polarity checker sends a known pulse or impulse through the system
  2. Cross-correlation of the captured response with the reference determines polarity
  3. A positive correlation peak indicates correct polarity
  4. A negative correlation peak indicates inverted polarity

Systematic Checking Procedure

During AES-2id alignment, check each component individually before combining:

  • Check each amplifier channel independently
  • Check each driver in a multi-way cabinet separately if possible
  • Verify polarity through each signal processing path
  • Document polarity settings for the system record

Common Mistakes

  • Not checking polarity until after detailed EQ work, wasting time
  • Confusing polarity (inversion) with phase shift (frequency-dependent rotation)
  • Correcting polarity at the wrong point in the signal chain

SonaVyx Tools

Use the SonaVyx polarity checker in the problem detection suite. Verify with the transfer function phase display. Check impulse shape with the IR tool. Monitor levels with the SPL meter. Get alignment recommendations from the AI diagnostic. Follow the PA tuning workflow.

Standard Reference

AES-2id:

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Last updated: March 19, 2026