Re: Carvin Legacy 3 advice on Speaker Set UP
so the easiest thing to do would be do as you said.
1 cable in to either cab using whatever setting the cab says to.
if the jacks are in parallel that means that the resistance is cut when both jacks are being used.
so lets say you have two 8 ohm cabs that you want to run at the same time. So you would run a single stereo/non-shielded cable to each. The total load on the head with two 8 ohm cabs would be 4 OHMs.
So the resistance is cut in half. Now if the jacks were in series the resistance would increase. two 8 ohm cabs would be running at a total of 16 ohms.
The good news is that a lot tube amps aren't too sensitive to mis-match imedance BUT You should never have your speaker load go below what the amp can put out.
So if the amp goes down to 4 ohms, never connect a load that would total less than 4 ohms.
BUT you can run your amp at a lower impedance than your total speaker load. So if you have an 8 ohm total load you could run your amp at 4 ohms. It isn't again recommended but shouldn't do any damage. You may notice a volume drop or your sound darken by loss of high end. Some times it is cool to do.
So after all that when in doubt just run at the right OHM rating. If you have other questions do a google search on speaker loads and or calculating total resistance in a curcuit. Mesa boogie also goes in the great depth about speaker loads in most of there user guides.