Zero autoformers -- how to measure impedance?

Hi guys,

I got a pair of speltz zero autoformers recently but when I measure the total impedance, my multimeter sees only 0.4-0.6 ohm no matter what I do. It seems the multimeter could only read the dc resistance from the autoformer itself but not the total impedance of the speakers and the autoformers. Is this normal? It's blowing my amp into protection mode.

Paul's website does mention something about using these with solid state amps that has excess offset voltages but I have no idea what that means....

Thanks,
Ryan