How is it you know it is your speakers that are going bad and not your amplifier? Usually it is the bose 7 ch amplifier that is the problem. The rear door speakers are smaller than 4 inch and are @3.75 inches and are 2 ohm . The fronts are 5 inch mids and a tweeter and are 2 ohm. If you are replacing the speakers you will be best off using oem speakers or replacing the amp and the speakers if you dont want to go with factory. We need to talk about the diagnosis before you replace the speakers.

Scott@lajollaaudio

__________________
The Mercedes Specialists Since 1986