Baldwin C-1 ext speaker/jack question

[JUDYDTMA]

Hi everyone!
I have a Baldwin C-1 Professional amp and am wondering how to get the most out of the 'EXTER. SPEAKER' jack in the back to potentially push another speaker or cabinet.
After researching on this forum, it's my understanding that this amp is putting out 2ohms into it's internal two 4ohm 12" speakers which are wired in parallel.
It's also my understanding that the external speaker jack is wired in series with the internal speakers.
So I'm wondering what the ideal setup might be for a two speaker cabinet (or possibly a single additional speaker) to give some different tone to the amp.
I'm primarily confused about how an external speaker/s that in series with a pair that's in parallel would work together.
I only have a basic understanding of parallel vs series and how the ohms of speakers in those scenarios affect the amp so the combination of two speakers in parallel and then adding one or more speakers in series with that has me confused as to what my various options are.
Any help would be greatly appreciated!

[DrGonz78]

Just think of it as a 2 ohm speaker in series with a 4 ohm speaker. 2 ohms will increase the output wattage. 4, 6 or 8 ohms will reduce overall wattage. I guess you could throw a crossover into the mix and use mid-high speakers to add more flavors. The idea of what it sounds like is subjective to your preference. The other factor is understanding how wattage affects each speaker or sets of speakers. It's best to evenly distribute the power output between speakers that have the same impedance and wattage limitations. So if you have an 100 watt amp and 2 speakers rated @ 50 watts each then you are good. Say you have one 75 watt speaker and the other is 25 watts it is not recommended. Mismatched speaker impedance can cause performance issues with the overall speaker load distribution. Any way you want to do it, it's best to balance the load across the speakers equally. I am sure there are some creative ways to do this!!