I have used 2 different cabs with my F-50. Both are home-built cabs. The one I've had the longest is built to the Mesa 1x12 Recto cab specs and is equipped with a V30...and while I generally run the amp through both the internal C90 and the external V30, I prefer the C90 and that's the speaker I mic for recording or performance.
More recently I built a 2x12 cab with a V30 and G12H30 paired together...currently it is open-backed, but I plan to mod it so that it can be closed if desired. But this cab sounds awesome with the F-50 for clean and mildy overdriven sounds...and if you get far enough away from it to really let the two speakers meld together, it sounds great even for high gain. After playing through this cab, going back to a 1x12 really sounds one-dimensional!! The problem is how to mic the cab if necessary...either speaker by itself is decidedly less satisfying, so you either mic both, or you do some sort of distant mic setup.
The V30 really emphasizes the midrange (which is almost too honky by itself for my tastes) and the H30 has lots of bottom end and highs, too. (One interesting discovery was the H30 by itself was NOT cool with the F50 at high gain...that really fizzy top end that is unique to Mesa really sounded harsh with this speaker...the response curve of both the V30 and C90 do a much better job of taming that...though using a beam blocker of some sort does help the H30 in that respect.) Anyway, this particular 2x12 really gives me a lot more bottom end than the C90, and it doesn't fall apart. So I find it interesting that while I would never choose either speaker by itself with this particular amp, together they're the bomb!
I actually built the 2x12 cab to use with a custom made 18W Plexi style tube amp that I hope to have in my hot little hands here in another week or so, but turns out it sings with the F50 as well!!
Never tried a 4x12, but would like to sometime.
