Does anyone know what size the front and rear speakers in a WRX are? I want to change my speakers but don't know what size the drivers are.

yeah I verify with cruthfield and they tell me is 4" and ok I remove the cover and found that looks like 4.5" but the 4" fits ok and very important don't buy a speaker with built in tweeter
the original speaker is joined to the cover of the door so if your speaker carry a tweeter the door cover will not fit with the door.

and for the front door is perfectly 6.5" and you can put a speaker with tweeter,there are enough space

as I know the front speaker are like mid Range high and voices and the rear speakers for lows, bass.

you could easily cut the rear door to fit tweeter into the upper part of the door. You could also get the