Mesa 4x12 cabinet: only using 2 speakers?

[Draytone]

Yes, that is what you want to do. Just want to make sure that you are running out of the correct impedance output on your head to match the new impedance of your cab when only running 2 speakers.

For example, if the cab is 8 ohm, there is a good chance that each pair could be made up of 2 8 ohm speakers in series which gives you 16 ohm, then those two pair are in parallel to make up 8.

So just make sure you are running out of the correct outputs and your should be fine.
-Rob