Room modes

Definition

A rectangular room supports standing waves. The first axial mode along length L is f = c / (2L) with c ≈ 343 m/s (about 57 Hz in a 3 m room). Width and height add their own combs; tangential and oblique modes fill the gaps. Peaks and nulls of 10–20 dB are normal. Treatment, multiple subs and EQ after measurement beat guessing from a calculator. The tool maps where the problems likely sit, not how to EQ them.

Calculators that use this

• Speaker placement & acoustics

  Room Modes / Standing Wave Calculator

  Map the first axial modes from length, width and height. Speed of sound 343 m/s. Then plan subs and treatment.

• Speaker placement & acoustics

  Subwoofer Room Gain Estimator

  Rough in-room bass lift from room volume and how many boundaries the sub sees. Add it to an anechoic SPL.

• TV mounting & DIY

  Helmholtz Resonator DIY Frequency Calculator

  Tune a ported cavity to a room-mode frequency: f = (c/2π) √(A / (V L_eff)) with end correction.