What would adding a 212 cabinet to my 212 combo amp do for my tone? Also, would it make the amp louder? Anything else that would change?
you will have a much better bass response and make it not louder but more full. I have a B52 212 combo hooked up to an egnater 2x12 and I love it!
it depends on how the amp is set up. if the amp is set up so that pluggin in an external speaker disables the internal one, then youll still only have sound coming from 2 speakers. if the 2x12" has nicer speakers and is good quality, it could improve your sound. however, if it doesnt disable the internal speakers, then your amp will sound a touch louder and be fuller.
it's not louder, but more full. also, speaker choice will alter tone. if you a run a peavey valveking through a marshall 1960 cab rather than the stock cab it'll sound much better.
I've got a thing about not having my amp up past 3 o clock volume. The cab I'm thinking of getting will have the same speakers as the combo, and the external out on the combo doesnt disable the internal speakers. I play mostly post-rock stuff, kinda mid-gain at the most. Will the cleans be warmer?
what kind of amp and which cab? and cleans are pretty dependent on your amp, but certain speakers certainly have a warmer tone. i.e. the celestion vintage 30 is much warmer than a celestion g12-75 or whatever.