How does the RM100 "see" a speaker via the ext jac

[Caine]

There isn't anything about this in my users manual... (RM100LB)

If I have an 8 ohm load via the main speaker jack, what would I set the ohms selector to if I connect another 8 ohm load via the ext jack?

Does the amp "see' that as TWO 8 ohm loads, in which case I would leave the selector on 8, or does it see it similar to adding speakers to the same cab, like either a series or parallel load, in which case, I would have to change the selector to either 4 or 16 ohms, depending on whether it's parallel or series.

So, what is the correct setting for two 8 ohm cabs using both jacks?

 

[eedude]

they are in parallel, so the load divides. If the speakers are the same impedance, then then load is halved (in your case 4ohms). So if you have two 8ohms cabs connected, set the impedance to 4 ohms.

Req = (R1*R2)/(R1+R2)
Req = 8*8/[8+8] = 64/16 = 4

it whacked the formula!
Req = (8*8)/(8+8) = 64/16 = 4