The impedance is 8 Ohm when you make sure to set the impedance switch on the volume controls to the proper setting, 1 to 2 zones; 2x. 3 to 4 zones set to 4X and 5 to 8 zones set to 8X on each of the individual volume controls. There is no protection in the SPW8 that is why we specify using Impedance Matching volume controls like our OSD SVC100 or OVC10 for outdoor use.
TL