Dayton Audio ND90-4 3-1 - Manual (Page 4)

The inductance components Le (x) and Bl(i) of most drivers have a strong asymmetric characteristic. If
the voice coil moves towards the back plate the inductance usually increases since the magnetic field
generated by the current in the voice coil has a lower magnetic resistance due to the shorter air path.
The nonlinear inductance Le(x) has two nonlinear effects. First the variation of the electrical impedance