I am an electrical technician so you don't have to worry about talking over my head, but I don't know too much about sound stuff. I work with large motors and controllers and generation plants and distribution centers. Audio isn't within my realm of reality, but if someone can give me a heads up here, I would appreciate it.

I have a guitar amp that is powered by two 6550 power tubes (meaning that it is about 60 watts max output) and the amp chassis itself says 120 watts rms at 4 Ω. It is a combo amp with two 12" speakers with no marking on them whatsoever. I have to assume that they are 60 watt speakers. I just put my dmm on the speakers and they are indeed 4 Ω. The amp is 40 years old. I think that 40 years ago, 4 Ω must have been more common than it is now, because all I can find in the 60 watt range is 8 or 16 Ω.

What will happen if I respeaker this thing with 16 Ω or 8 Ω speakers? Will the amp not be as loud (less load on the output side?) Or will it not drive the speakers?

Can anyone help me out here?
if you respeaker the thing with 2 8ohm speakers in parallel, you'll get 4 ohms
Won't drive the speakers as loudly. It can also stress the output transformer in more extreme cases.
I'm not very active here on UG currently.
I'm a retired Supermod off to the greener pastures of the real world.