[RodB]

The schematic shows 3 wires running to the speaker. Your speaker has 2 coils, one is the voice coil that makes the cone move and the other is the field coil magnet that creates the magnetic field so the voice coil can do it's thing. In addition the output transformer is also mounted on the speaker basket. The field coil is typically the choke coil in the power supply. If you look at the schematic, it shows the field coil in the power supply filter circuit. The B+ output voltage from this power supply is connected to the primary winding of the output transformer; this is one wire. The other end of the output transformer primary is the other wire and the third wire is the other end of the field coil. Very dangerous voltages running external from chassis to speaker.