Theater Calculators
Room Modes / Standing Wave Calculator
https://www.theatersizing.com/calculators/room-modes/
Estimate only — not a calibrated SPL meter, an acoustic report or an electrical design. Confirm with measurement.
Room Modes / Standing Wave Calculator
The first axial mode along a dimension is c / (2L). Peaks and nulls of 10–20 dB are normal. Multiple subs beat a single EQ notch.
Inputs
Results
- Length axial
- 31.2Hz
- Width axial
- 42.9Hz
- Height axial
- 68.6Hz
- Schroeder-ish bound
- 191Hz
Calculation method
f_L = 343 / (2L) and likewise for width and height. Schroeder bound assumes T60 = 0.5 s: f_s = 2000 √(0.5/V).
Exact formula
f = 343 / (2L). f_s = 2000 √(0.5/V). Limits: rigid rectangular room, no furnishings, first axials only, T60 0.5 s assumed not measured, air at 20 °C.
Axial modes only
Each axis is f = 343 / (2L) with 343 m/s. Tangential and oblique modes are omitted, so a clean-looking chart can still boom in a corner. Use this to see which dimension is likely to pile energy near a crossover, then measure.
Schroeder assumes T60 of 0.5 s
The transition frequency is 2000 √(0.5 / V) with T60 fixed at 0.5 s. A dead, heavily treated room drops Schroeder; a live plaster box raises it. The chart is not a substitute for a decay measurement.
Frequently asked questions
Why 343 m/s?
Speed of sound near 20 °C. Cold rooms shift a few hertz.
Only three frequencies?
Those are the first axials. Harmonics sit at 2f, 3f… Tangentials fill the gaps.
Will EQ fix a null?
Not at the seat. Move the sub or add another.
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