Acoustic diffuser geometry / shop reference

BarrelCalc

Circular-arc geometry calculator for hand-built acoustic barrel diffusers

Standalone · Local calculation · v5.1

Choose two known construction dimensions; BarrelCalc resolves the complete circular segment and draws the resulting barrel profile to proportion in real time.

Define the arc

Pick the two dimensions you know.

Solve from

Units

Shop interpretation

Arc length is the curved face material length. Width is the straight chord from edge to edge. Height is the crown projection above that chord.

Full arc geometry

Live proportional drawing · measurements update as you work.

diffuser face construction dimension radius / center

Calculated geometry

Ideal circular segment dimensions. Area is the 2D area enclosed by the arc and chord.

LAYOUT

Building the profile

For a rib or end-form template, mark the chord width, locate its midpoint, then rise by the sagitta to establish the crown. The calculated radius and center point give you a compass/trammel layout when the center is physically reachable.

MATERIAL

Allow for thickness

BarrelCalc describes the ideal reference arc. When bending plywood, laminate, sheet metal, or another skin, decide whether your specified radius is the inside surface, outside surface, or neutral axis and adjust for material thickness.

ACOUSTICS

Geometry is only part of diffusion

Physical size, radius, array spacing, boundary conditions, and wavelength all affect scattering. Use this utility for fabrication geometry; verify acoustic behavior separately when performance targets matter.

Chordc = 2R sin(θ/2)

Sagittas = R[1 − cos(θ/2)]

Arc lengthL = Rθ

Segment areaA = ½R²(θ − sin θ)

Angle convention: θ is expressed in radians in these formulas, including L = Rθ. BarrelCalc accepts and displays the subtended angle in degrees (°) and converts it to radians internally for calculation.