One of the ways manufactures can save on the total cost of an audio system is by cutting the costs of the crossovers. As digital processing has evolved one might assume that factory wiring and amps would put out tightly controlled audio signals to each and every speaker independently. However, that is not true for the vast majority of cars. To see how I crafted the crossovers for the front door mid-woofers check out the mid-woofer upgrade post.
The drivers that are used in luxury cars are often numerous and of various non-standard sizes. While upgrading the main playing drivers makes a lot of sense, the difficulty increases and return decreases greatly when we are discussing the rear surround for example.
In these cases, it makes a lot of sense to control the frequencies theses small drivers are getting fed. So that when you turn up the volume, the sound remains clear and undistorted for longer. On the center channel I added two capacitors but upon reflection of the wiring diagram the center channel is not a summation of two speakers but one connector seems to be for SOS and Mercedes calling, and the other, it seems like right side is for the music. I'll try to remove the left capacitor in the future to come back and check to see if that is the case.
To remove the front grid, you use a straight plastic pry tool. releasing 4 tabs near the you. The windshield side is attached by lifting up and out. Remove the front two connectors carefully. Once at the speaker pry gently on the center speaker and splice inline a 68mF capacitor on the right connector solid color.
Remember to always insulate any metal
For now I can say that with the volume all the way up, the front stock does not distort when paired with a 68mF capacitor. It does sound a bit bright for my tastes, but I like bass, and with a subwoofer I'm sure it will sound good if I ever decide to go into logic 7 mode.
In the rear it looks like the easiest way to add cross overs is from the trunk amp. I would look at the stock wiring diagram and find the surround left and right + output and inline splice a 68mF capacitor. These 68mF capacitors should pass frequencies of ~600hz and above. Protecting these small woofers from trying to play frequencies they cannot. Which I guess would be some where close to 400hz but have not tested.