Voice Coil Lab Notes: Improved Zobel Network
Passive crossover filter networks for multi-way loudspeakers generally require a resistive termination for optimum performance. The driver itself generally presents a reactive load. Inductive rise with frequency above resonance of the loudspeaker electrical impedance is semi-inductive due to eddy current losses. The L2/R2 impedance model represents the electrical impedance as seen by the amplifier output. An improved compensation network can be realized by using the analogous circuit “dual” of the L2/R2 model. This represents a dramatic improvement to the basic two-component Zobel network and compensates for the non-ideal semi-inductive behavior of the loudspeaker driver across the entire frequency band.