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

EQ Recommendation per AES-2id

TL;DR

AES-2id system alignment methodology provides the framework for data-driven EQ decisions. EQ recommendations should be based on transfer function measurements with high coherence, applied only to correct system deficiencies that cannot be addressed by physical means (speaker positioning, aiming, acoustic treatment). SonaVyx AI diagnostic engine analyzes your transfer function measurement and generates parametric EQ suggestions following AES-2id principles: correct the system, not the room. The recommendations include frequency, gain, and Q for each filter, with confidence indicators based on measurement coherence at each correction frequency.

AES-2id EQ Philosophy

AES-2id teaches that EQ should correct system deficiencies, not room acoustics. The distinction is critical: system deficiencies show as consistent features across positions (coherence above 0.8), while room effects vary with position (coherence below 0.7).

EQ Decision Framework

  • Only apply EQ where coherence exceeds 0.85 (the measurement is trustworthy)
  • Prioritize broad corrections over narrow ones (shelving filters over parametric notches)
  • Address magnitude deviations greater than 3 dB from target
  • Limit total EQ to 12 dB of boost and 18 dB of cut

Types of EQ Corrections

  1. High-frequency shelf: compensates for air absorption and reverberant HF buildup
  2. Low-frequency shelf: adjusts bass balance for room proximity effects
  3. Parametric cuts: removes narrow system resonances visible with high coherence
  4. Parametric boosts: fills narrow dips caused by speaker pattern characteristics

What EQ Cannot Fix

EQ cannot correct room modes, comb filtering from reflections, or reverberant energy. These require physical solutions: speaker repositioning, acoustic treatment, or subwoofer optimization.

Common Mistakes

  • Applying narrow EQ cuts to room-induced dips that vary with position
  • Boosting frequencies where coherence is low
  • Using more than 10 parametric filters (indicates underlying physical problems)
  • Not verifying EQ changes with a follow-up transfer function measurement

SonaVyx AI EQ

Get AI recommendations from the SonaVyx diagnostic engine. Measure with the transfer function. Monitor changes with the RTA. Verify levels with the SPL meter. Check for issues with the problem detector. Follow the PA tuning workflow for structured alignment.

Standard Reference

AES-2id:

Try It Now

Open this measurement tool in your browser — free, no download required.

Open Tool
AP

Design your room acoustics with AcousPlan

acousplan.com →

Last updated: March 19, 2026