I'm putting my new Emi Wizard/Governor speakers in a 2x12 cab. I need to wire them in series so I get 8ohm + 8ohm = 16ohm. No problemo. However I want to make it switchable with DPDT switch so I can run stereo (each speaker individually at 8ohm) and mono (16ohm combined). I am 90% there but I have one question with the attached diagram. The area that I circled (in black). Is that implying that there are are two wires connected to the same sleeve lug on that jack?? Is this ok to do since it's negative? I can't see any other way to get the single connection from that sleeve to the two lugs shown on that switch. Im hoping its just something simple that I'm overlooking. Any help greatly appreciated.


You've basically got it right. You'd usually wire that by wiring the jack straight to one lug on the switch and then using a short jumper wire to connect that lug to the other one. It's the same thing electrically but it's a little cleaner/sturdier and uses less wire.

Looking at the switch now, only one of those top lugs in each left/right cell is ever connected to another part of the circuit at one time. Those black slash marks in the switch show what connections are made in each switch position. When you flip the switch, they move from the left lug to the right one in each cell, connecting that lug to the bottom lug. So in the diagram, the right lug on both halves is not connected to anything, it's just hanging out in the switch and it's a dead end for electrons. When you flip the switch, the left lugs are disconnected and the right lugs are connected to the bottom lug, and now you have a completely different circuit. 

So it doesn't matter if it's negative or positive (which is good because that's kind of a fake idea on a speaker anyway) but because the switch only connects one of those lugs to anything at one time, except perhaps when the switch is actually flipping between one and the other, and hopefully you're not doing that with your amp turned on. 
I'm always a fan of figuring stuff out yourself but it may be easier to just buy something like this and it switches when you plug in the amps - https://avatarspeakers.com/shop/parts/guitar-input/
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