Originally Posted by RickenBoogie
What specific Celestion driver? It's doubtful ANY replacement spkr is an actual "upgrade".
I heartily concur with this, as I doubt that the original design of the cabinet was optimised for the celestion drivers.
There is however nothing at all wrong with celestion drivers in general.
And operating in a cabinet designed to make use of there Thiel small parameters might indeed be a small upgrade.
The only real test for this is trying it live, back to back with a stock one.