Bass Trap

An acoustic absorber specifically designed to control low frequencies, typically placed in room corners.

A bass trap is an acoustic treatment designed to absorb low-frequency sound energy, typically below 300 Hz. Standard thin absorbers are ineffective at bass frequencies because their thickness is small relative to bass wavelengths.

Effective bass trapping requires: • Thickness: 4"+ of porous material for meaningful absorption below 200 Hz • Placement: Corners where modal pressure is highest • Coverage: Significant surface area for measurable impact

Common bass trap types: • Porous velocity traps: Thick fiberglass/rockwool panels (simplest, most common) • Membrane/panel traps: Tuned to specific frequencies using a vibrating panel • Helmholtz resonators: Cavity-based traps tuned to narrow frequency bands • Diaphragmatic: Combine mass and damping for broadband absorption

Corner placement is optimal because room modes create pressure maxima at boundaries. Tri-corners (where ceiling/floor meets two walls) are most effective, followed by dihedral corners (two surfaces meeting).

Bass trapping is essential in small rooms where room modes create significant peaks and nulls in the frequency response.

Practical Example

A room with strong 80 Hz mode

Wavelength at 80 Hz: 343/80 = 4.3 meters

Effective absorption needs treatment at least 1/4 wavelength (1+ meter) thick, or strategic corner placement of 4-8" panels.

Glossaire · Concepteur de Diffuseurs

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