What size speakers are in a Mazda 5?

Replace the head unit before you do anything else. The rear speakers put out a much better sound than the front with the stock H.U. I'm guessing this is a crossover problem because they are components in the front doors. But for me sitting up front I have too much on the high end and next to nothing on the low end. I've found crutchfield.com is the best source for info and hardware.