new amp comin - question

Hi guys, this doesn't have very much to do with guild, other than i will be playing a guild bass through it, but i figured someone here could surely help me out

If everything goes right, I should be getting my Peavey VB-2 head tomorrow. I'm super excited.
However, I have a quick question pertaining to cabs and ohms. The two cabs I would like to run with this head are my 1x18 (8ohm) and my 1x15 (4ohm).
Now, if my understanding is correct, 8ohms+8ohms=4ohms and 4ohms+4ohms=2ohms. 8ohms+4ohms= about 2.6667ohms right?
The head has an ohm switch on the back ( 2, 4, or 8 ).
Could I run these cabs?

mellowgerman said:

The two cabs I would like to run with this head are my 1x18 (8ohm) and my 1x15 (4ohm). The head has an ohm switch on the back ( 2, 4, or 8 ). Could I run these cabs?

Click to expand...

Hi Ingo: You might want to look Here. It addresses two speakers in parallel but they assume the speakers are in the same cabinet. In that configuration, the arithmetic for speaker #1 (S1) and speaker #2 (S2) is; (S1 X S2) / (S1 + S2); or, for your speakers; 32 / 12 or 2.75 ohms. You need to confirm that the primary and auxiliary speaker jacks are wired in parallel. If yes, you could run these cabinets off the 4 ohm taps. CJ