Difference in Revel F52 series speakers

What was changed from the original F52 to the Performa2 F52? Anyone get a chance to listen to both? Is there a big difference in the sound?
I listened to the M105/106 and they sounded very good..imaging was amazing. They are part of the Performa 3 series and im pretty sure the revel website explains the difference.
I listened to both when they were new to the product line.
I own the F32's as the budget wouldn't stretch to the F52's.
But I remember that F52's Performa2 had much better delivery and presentation across the board. But I have also listened to the new Performa 3 series and now am wanting those as they offer a distinct improvement of the Performa 2's. They just keep getting better.
did you mean the f-50 to the f52? if so the f52 fixed problem with the f 50 drivers.