Theater Calculators
Helmholtz Resonator DIY Frequency Calculator
https://www.theatersizing.com/calculators/helmholtz-resonator/
Estimate only — not a calibrated SPL meter, an acoustic report or an electrical design. Confirm with measurement.
Helmholtz Resonator DIY Frequency Calculator
A bottle is a Helmholtz resonator. Build a cavity, a neck, and you can notch a single nasty mode. Measure after you cut.
Inputs
Results
- Neck area
- 0.0020m²
- Tune frequency
- 33.8Hz
Calculation method
A = π(d/2)². L_eff = L + 0.8√A. f = (343 / 2π) √(A / (V L_eff)).
Exact formula
f = (c/2π) √(A/(V L_eff)), L_eff = L + 0.8√A. Limits: no lining, no leaking joints, one degree of freedom, 20 °C.
Frequently asked questions
Multiple necks?
Sum the areas, keep L_eff honest, or you are guessing.
Fill the box?
Light fill lowers Q and shifts f a little. Recalculate after you stuff.
Port on the face?
End correction assumes a flanged-ish opening. Flush ports are close enough to start.
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