Demodulation rings substantially reduce the harmonic and intermodulation distortion associated with voice coil displacement. They also reduce the modulation of magnetic flux during the movement of the voice coil to make the variation of system inductances more linear as input current varies.
The shorting ring is more effective (than the rest of the magnet assembly) at conducting away the unwanted electrical. This reduces inductance (Le) within the motor circuit.Circuit inductance can have the negative effect of reducing the speaker’s SPL, when input power is high (so-called power compression). Lower motor circuit inductance = less power compression.