Hi Guys,
A lot of people wonder if they can fit 5.25" speakers in the front dash of their W124, especially those without door speaker panels like myself. Rainbows are obviously the only "drop in" replacement, 4" speakers don’t fit properly, and you really need some kind of bracket because the hole is slightly larger than 4". Similarly, people usually only put 5.25" speakers in the rear unless they go for the chop under the headrests or medkit. I wanted the best sound I could get from these locations keeping the look totally stealth, ie grilles fitting over the speakers perfectly so no one would have a clue what you have under there.
Front Dash Speakers
I used Infinity Kappa 52.7i's for this location. These have a compact neodymium magnet that makes for big power plus easier fitting inside the dash. Other 5.25"s will fit, I tried some "chinese" ones successfully too, the smaller the speakers cut out is the better. For the chinese speakers the cut out diameter was small enough that the only cutting I needed to do to the dash I could do with box cutters! With the Infinitys it was a little more difficult so I used a Dremel tool. A lot of people are worried about cutting up their nice Mercedes, so was I but if you are careful and just cut the diameter out a tiny bit at a time there is nothing to worry about. Plus these speakers are going to stay with this car for the rest of its life, and any cutting I did is hidden under the grille.
mmm.... stealthy
Rear Speaker
I was quite baffled as to what to do with the rear speakers; the options seem limitless if you are going to cut thru the medkit. I decided I still wanted to keep the install stealth and try install some decent speakers under the oem grilles. This would also leave room for porting a subwoofer through the medkit if I ever got around to that (which I doubt I ever will now). 5.25"s do not fit perfectly into the brackets that the oem's sat in so I felt that I would have to make my own bracket. Whilst doing this I wondered if 5x7"s could fit with my own bracket, yes they could I decided. I chose Polk EX357s. The reason for these is that they are truly 5 inches by 7 inches and not verging on 6x8s like Infinitys and other higher end brands. 6x8s would not fit.
I made a bracket out of MDF using predominately a jigsaw and a file. It was a bit of trial and error to get it to sit properly onto the uneven steel rear deck as you can see.
I got there in the end but also had to cut a small bit out of the original speaker hole for the magnet to fit in. Because of the 5x7s elongated shape the magnet sat too far back to fit nicely in the original hole, I used the jigsaw for this.
Further, the speaker grille sat nicely over the top and the rubber rollover edge of the speaker cleared the shelf.
Amplifier
I run all 4 speakers at half gain on my 4x80WRMS amplifier that I have riveted under the parcel shelf. Of course if I was to buy a subwoofer this would be pulled down from there.
Conclusion
All in all the system is unreal. The bass response is very strong and clear although you do need to turn it up a bit to get the strong bass, this is the trade-off of having higher-end speakers. The bass is slightly stronger from the Polks in the rear, they are rated 10Hz lower than the Infinitys but I am guessing the "box" that is made with the trunk may help in this regard compared to the cramped "box" under the dash of the Infinitys. I run it off an old Alpine stereo (takes some of the stealthiness away I know), I would love a new Becker system though. The mids and top end are perfect and with the windows down you can hear lyrics from songs clearly over 50 meters away. As expected you don't get the same from the bass but in the car the bass is more than enough, hence why I will probably never get around to installing a subwoofer, I simply don't need it now, not for my listening pleasure.
Cheers with your install guys, hope this gave you some ideas and guidance.