I think of it as the "cardboard" parameter.
I totally got this wrong earlier and voted wrong... it's ROOM that I turn up.This!
Not a big fan of air but I love the room parameter.
i prefer the dephase parameter over air
Try it with a distorted tone.
To hear its effect by itself, mute all cab channels except one, point that one to an empty cab slot, and then turn up AIR.
I used to add AIR, years ago. I don't anymore and I don't miss it. I think of it as the "cardboard" parameter.
Ah that’s where I was gas going wrong, I play clean (rare I know ).
Clean is cool ... recently on the III been playing the #2 & 4 quack pos w/ an S-type, on SLO, Fender and Mesa - all with a fair amount of volume for those thumps and responsiveness, and just loving it. (but eventually I fall for moar ... gain and bridge PUp ... it's just so addictive. )