Bass Trap Calculator
Size a porous bass trap (quarter-wavelength depth rule) or a tuned membrane trap (f₀ = 60/√(m·d)) to tame a low-frequency room mode, with panel thickness by material, a room-mode targeting helper, and corner-placement guidance.
ℹ These are standard design approximations, not exact predictions. A porous absorber doesn’t switch on at one frequency — its absorption rolls off gradually, and the real figure depends on the material’s density and flow resistivity and how it’s mounted. A membrane trap is narrowband and must be sealed airtight to work. You’ll usually need several traps, and corners matter most. Use the numbers to size and place traps, then confirm by measuring (Room Frequency Analyzer). Metric; everything runs in your browser.
How It Works
Bass problems come from room modes — standing waves between parallel surfaces that boom at some notes and disappear at others. Two kinds of trap absorb that low-frequency energy. A porous trap (thick mineral wool or rigid fibreglass) absorbs by friction as air moves through it, and air moves fastest a quarter-wavelength out from a wall — so a porous trap of total depth d only starts working well around f ≈ c / (4·d). To absorb a 50 Hz mode that way you’d need roughly 1.7 m of depth, which is why porous traps are mounted thick, across corners, with an air gap behind to add effective depth. A membrane (panel) trap takes a different route: a limp panel of mass m over a sealed air cavity of depth d behaves like a mass on a spring and resonates at f₀ ≈ 60 / √(m·d), soaking up energy near that frequency without needing huge depth. The trade-off is that it’s narrowband and must be airtight.
Both formulas are approximations: a real porous absorber rolls off gradually rather than switching on at the quarter-wave point, and its absorption depends on density and flow resistivity; a real membrane’s tuning shifts with how the panel is fixed and how lossy it is. Use them to size a trap, then place traps where they work hardest — in the corners, because every axial mode has a pressure peak in every corner, so a single floor-to-ceiling corner trap attacks them all. Enter your room dimensions above to see your lowest axial modes and target the worst one first, then verify the result with a measurement.