Speaker Electromagnet Simulator (2D)

Drive signal

Frequency 40 Hz

Current amplitude 70%

Driver

Motor force factor Bl 1.0×

Suspension damping ζ 0.20

Driving the coil below resonance.

Live Readout

Coil current I

0.00 A

Force F = BIL

0.00 N

Displacement x

0.00 mm

Resonance f₀

40.0 Hz

How it works

A voice coil sits in the radial magnetic field of a permanent magnet's gap. Driving it with a current I produces a Lorentz force on every turn of wire, F = B·I·L (field strength × current × total wire length, lumped here into a single "motor force factor" Bl). That force pushes the coil — and the cone glued to it — back and forth.

The cone doesn't move in lockstep with the current: it behaves like a mass on a spring with damping, m·x″ + c·x′ + k·x = F(t). Near the driver's natural (resonant) frequency f₀ = (1/2π)·√(k/m), even a small force produces a large displacement — the classic resonance peak. Drive far above or below f₀ and the same current barely moves the cone. Raising the damping ratio ζ flattens that peak and settles the cone faster; raising Bl scales the force (and the sound output) for the same current.

Sweep the frequency to find the resonance peak