i put it in an avatar 2x12 next to another wgs green beret thats at least a few years old now.
the brand new speaker sounds noticably fizzier than the old one. am i to assume i need a break in period and the fizz should eventually dissipate or is there something off with my speaker?
Yes. You will have a breakin period for that speaker. Play it for a week at least and see if it doesn't smooth out some. A speaker you've been playing on for two years should sound noticeably different than a brand new one. That's pretty normal.