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

RTA Measurement per AES-2id

TL;DR

The RTA is the workhorse display for AES-2id system alignment, providing continuous spectral feedback as you make adjustments. While the transfer function gives the most accurate system response measurement, the RTA gives you instant visual feedback during hands-on work: adjusting EQ, setting crossover levels, and verifying coverage at walk-around positions. SonaVyx RTA mode with configurable smoothing and trace store lets you capture snapshots at different positions and overlay them for coverage comparison, directly supporting the AES-2id methodology for systematic sound system optimization.

RTA in AES-2id Workflow

The AES-2id system alignment process uses RTA at multiple stages: initial system check, gain staging, EQ adjustment, and final verification. The RTA provides the fast visual feedback needed during active tuning.

Gain Staging

  • Send pink noise through the system at nominal level
  • RTA should show approximately flat response within broad tolerances
  • Gross deviations indicate hardware issues to address before fine tuning
  • Store the initial RTA as a reference trace

EQ Adjustment Monitoring

  1. Display the live RTA while making parametric EQ changes
  2. Use 1/3-octave smoothing for broad EQ, 1/12 for narrow corrections
  3. Compare live trace against stored reference to track changes
  4. Monitor coherence (via transfer function) to ensure changes are meaningful

Walk-Around Coverage Check

Carry the measurement microphone through the venue while watching the RTA. Store traces at key positions. Overlay all traces to visualize coverage uniformity across the space.

Common Mistakes

  • Making fine EQ adjustments based on RTA alone without transfer function confirmation
  • Not using trace store to compare positions
  • Chasing room modes with parametric EQ instead of addressing them acoustically

SonaVyx Tools

Use the SonaVyx RTA for real-time monitoring during adjustments. Verify with the transfer function for precise measurement. Check levels with the SPL meter. Identify issues with the problem detector. Get AI recommendations from the diagnostic engine. Follow the PA tuning workflow.

Standard Reference

AES-2id:

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Last updated: March 19, 2026