Disclaimer: Variations in MB model years and in after-market speaker brands may require alteration of the procedures shown. This procedure was employed for mounting 6 1/2" Diamond Audio 2 way speakers. Other speakers may be larger or smaller, and therefore may be less work, more work, or impossible to fit using this procedure. Use of tools and power equipment should follow all accepted safety practices, including use of eye protection.
Screwdrivers (Phillips and Slot), Wire cutters/strippers/crimping tool, soldering iron, Dremel tool/fiberglass reinforced cutting blades, power drill with selection of bits, Quality electrical tape, adhesive backed foam weather strip roll (Thickness determined by your speaker selection), a selection of speaker spade and bullet connectors.
The front door speaker panel is secured from the bottom by a single Phillips screw. After the screw is removed, the grill is simultaneously tilted down from the rear and forward to free the plastic mounting ears from the door panel.
Removal of the grill exposes a roughly 5" paper speaker on a 6" plastic frame. The frame has 3 mounting ears - two at the front edge of the door, and one at the lower rear of the speaker frame.
Removing these 3 screws causes the speaker/frame to hang by the wiring, so care is needed while removing the speaker screws. While supporting the speaker, cut the wires as close to the terminals as possible, leaving a small section of the colored insulation on the terminals to help ID the polarity match to the car wiring. Polarity was indicated on my car with a "+" stamped on the plastic frame/speaker assembly.
After the speaker/frame is removed, the plastic vapor barrier covered door sheet metal and plastic dust/moisture shield for the speaker is exposed.
The speaker and frame/spacer assembly need to be disassembled and modified to fit your speaker. Planning, dry runs, and careful work are required at this point. This assembly consists of the speaker, spacer/frame, and foam insulation.
The speaker was glued into the spacer/frame at the factory with a black silicone-like adhesive on my model. Some of the adhesive is visible in the top center of the picture at left. Careful use of a thin small slot blade screwdriver allowed the adhesive to be scraped off from the front and rear of the speaker. It was especially thick around several tabs on the speaker that inserted into slots in the spacer/frame, but was removed with less than 10 minutes work per speaker.
After the adhesive was removed, the speaker was easily pried out of the frame on my car. The foam strip on the front is adhesive backed, and may be removed for re-use with a little care. (figure 7) Please note that the plastic spacer frame is not a flat surface on the speaker side - there is a pronounced bow in the middle of the mounting surface.
Removing the foam strip as above reveals a vertical extension of the spacer/frame, and a horizontal 'shelf' for the foam strip. The vertical extension protruding upwards from the frame acts as a 'fence' to keep the foam strip away from the speaker cone. Depending on the mounting depth requirements of your new speakers, this 'fence like' vertical extension may need to be cut off flush with the horizontal 'shelf' with a Dremel tool. Do not cut off the circular 'shelf' that protrudes horizontally from the sides of the spacer/frame - this is needed for mounting the new speakers. Using a thin cardboard template (which is often provided with aftermarket speakers - if not, you will need to make one matched to your speakers), mark appropriate mounting hole locations on the spacer/frame. You will need to mark these holes in a way that accommodates the way the spacer/frame is mounted on the door, and to have the speaker screws clear the storage bin/door pull overhang. Placing the frame back against the door before drilling the holes will allow you to visualize the clearance of the mounting screws. Likewise, visualization of the way the speaker terminals will clear the spacer/frame is useful. These methods will vary for each speaker, but usually there are a variety of holes in the speaker frames to allow secure attachment while clearing all the above obstacles.
Once you are convinced the speaker mounting holes are in the best position for your brand speaker and will clear all obstructions and be easily accessed, the holes can be drilled. After drilling, a Dremel tool can be used to cut a slot parallel to and immediately below the horizontal circular flange at the location of the mounting holes you just drilled. If you left the top vertical flange in place, a second slot will need to be cut with the Dremel tool on the top side of the horizontal flange at the speaker mounting holes you just drilled. These slots you cut allow speed nut clips to be inserted and accept the speaker mounting screws. Since the surface of the spacer frame is not flat, adhesive foam strips must be used to acoustically isolate the front of the speaker from the rear. Place the foam strip (you can re-use the factory strip if you were careful when it was removed) over the speed nut clips, making sure the holes aren't blocked. The foam strip should be thick enough to completely fill the space and compress between the speaker and spacer/frame when they are attached together, so that sound is isolated between the front and back surfaces of the speaker. Place the speaker over the spacer, and temporarily screw it in place. Do not over-tighten - the speaker only has to be held in place, not cinched down tightly, as that can distort the speaker basket and damage the speaker. The goal is to keep the speaker front acoustically isolated from the rear, and just secure enough to not move on the spacer frame.
At this point it is useful to make a 5-6" speaker wire harness with spade terminals on one end that can attach to the speaker terminals, and bullet terminals on the other that can be attached to matching connectors you will install on the car speaker wiring. Observe polarity and color coding when preparing this harness to avoid connection mistakes later. This harness can be attached to the terminals, and fed through one of several holes in the side of the spacer/frame. All the holes in the sides of the spacer/frame should be plugged with foam and taped over for best isolation of sound waves. If done correctly, the speaker wires will protrude from the side of the spacer/frame by the single mounting tab, not the side with two mounting tabs. The car wiring easily leads to this same area, and connection is mad at the side of the speaker, not behind he speaker, simplifying installation.
Now it is necessary to test fit the speaker/spacer frame/wiring harness back on the car. If you used a speaker with a small magnet, such as neodymium magnet speakers, or a brand with shallow mounting depth and little or no tweeter protrusion, the rest of the installation may be as simple as re-attaching the 3 spacer/frame screws, connecting the wires, and re-installing the grill! However, if you used a speaker with a large magnet or with large protrusion of the tweeter from the center, more work is in order.
The Diamond Audios have both a large magnet, and a 1/2" tweeter protrusion. To make these speakers work, I needed to remove the protruding flange as discussed above, allowing the speakers to be mounted about ?" deeper away from the door grill. Unfortunately, this makes clearance of the large magnet a tough proposition. As can be seen in the picture at left, the plastic dust shield on the inside of the door sheet metal is not perfectly centered, isn't perfectly circular, varies in depth relative to the door sheet metal, and the sides are irregularly shaped! For the Diamonds to fit, the back of the dust shield had to be removed about 3/4" from the louvers in the bottom! This was pretty much trial and error cutting with a Dremel tool in a well ventilated area. (Plastic fumes from cutting!) Care was used to probe for wiring or mechanical obstructions prior top cutting. While there were no real close wires or mechanical bits to interfere on my car, yours may be different, so check before cutting. A hand vacuum with extension wand was used to remove plastic waste from inside the door. Even with this material removed, the 3 mounting tabs on the spacer/frame had to be slightly key-holed to allow the assembly to be attached to the door. Also, a strip of flexible foam was used to make a 'roof' over the back of the speaker for dust and moisture protection. Several audio catalog stores have foam baskets for various speaker sizes that can be cut with scissors to make an appropriate flexible shield.
Once installed and connected, and tested to your satisfaction, the only remaining step is to re-install the door grills. Additional foam strips can be placed around the rim of the speaker, taking care not to touch the rubber speaker surround.
Special thanks are in order to forum member SCLJA, (Scott at www.lajollaaudio.com) for all the expertise and telephone guidance that he and his staff provided during speaker selection and the installation process. I was not convinced at first that everything would clear, but with their expert help, it all worked out, looks stock, and sounds fantastic.