You know, this question about ohms and multiple cabs shows up about every day. Along with this question comes some responses that are either bad advice, just plain wrong, or even dangerous for the equipment. 1) You cannot rewire a cab from 4 to 8 ohms or vice versa. At least I can't think of a cab configuration where you can do this 2) Don't tell people they can run a 4 ohm and an 8 ohm cab together unless a) the 4 ohm cab can handle twice the power of the 8 ohm cab or b) the amp can in question can handle sub-4 ohm impedances. 3) Don't suggest going to series connections or some combination of parallel/series via cables outside of the cabinet. Besides the power handling mismatch of the cabinets (see #2), going to a higher impedance results in less power from the amp, even if it is feeding an increased speaker area. The net gain is usually zero or not worth it. Also, building up some kind of series or series/parallel speaker cable is just asking for trouble. You now have a non-standard cable that is probably unmarked and may cause problems if used somewhere else. Besides that, unless you also build a spare cable, you are in trouble if your special cable fails. Plus, inadvertently plugging in standard cables risks damaging your equipment. Don't tell me that you will be the only one plugging your rig together. Band mates or sound guys helping out may not be aware of your special configuration. Discuss.