[Arran]

Before you give up on the speaker, you may want to check it over carefully to make sure that it didn't suffer from a broken lead going into the field coil. I will have a look at how the speaker on my console is wired, some sets had four pin plugs but one wasn't connected to anything since one side of the output transformer was often connected to the output side of the field coil so a fourth wire was unneccessary. Resistance of my field coil won't help you, it has a 12'' in it not a 6''.
Regards
Arran