教科書正解(Introduction to Electroacoustics and Audio Amplifier Design, W. Marshall Leach Jr):
"The voice-coil impedance of a loudspeaker driver is not purely resistive. This can have a major perturbation
on the performance of crossover networks...A matching network, sometimes called a Zobel network, between the crossover network and the voice-coil terminals of a driver can be used to cause the effective load on the crossover network to be resistive."
