Put a pair of Image Dynamics 4" Coax speakers in the dash of my 300D Turbo and I'm *very* happy with them. They really get the music right. A tad on the thin side, but these are 4" speakers. Keep in mind we are talking $125 coax speakers and not Dynaudio or Focal. I have one of their Subs in the trunk that I like very much also altho it's hard to hear when this thing is built like a tank.

http://www.imagedynamicsusa.com

If your having trouble hearing the sub why don't you take out the rear speakers (give it a,try trust me) or put a port through the fist aid kit area?
Just a suggestion...

I sort of like the rear plates in the back. If I could figure out a way to use the first aid kit for a port I would. The gas tank is right in the way. I also don't really want any extra road noise from the trunk. The Image Dynamics 10" sub will actually penetrate the fortress somewhat. How much difference does it make taking out the rear speakers?

Taking out the rear speakers makes a HUGE difference... Try it.. they're very easy to pop out. Probably treble the volume. Careful, cos at the moment you're probably driving your sub so loud so you can hear it that its distorting.

You *can* cut under the first aid kit, but the metal is THICK so take care. Also, cut upwards, from the trunk into the cabin. This way you dont drill holes in your gas tank!

Bri

I wonder what would happen if i just take the first aid kit out? i could put some grille cloth there i guess. my sub does work harder, but it's not distorting at all. not a lot of bass gets thru the fortress.

Taking just the first aid kit will do nothing... theres 2mm thick metal, with a 5mm rubber coating and a thick pile of carpet in the way.

Are you *sure* its not distorting? Distortion (the *WHACK* sound as it hits the end stops/amplifier clips) is a treble thing. Treble will not come through that rear shelf at all, so you wouldnt hear it. Perhaps stick your head in the trunk and listen

Bri

For what it is worth, I have had the rear speakers out for 3 months while my stereo project has been on hold - not a real noticable difference in noise. Those paper cones didn't seem to make much difference in the noise reduction.

If you are intent in cutting the rear deck, it might be worth looking in the trunk under the first aid kit. On my 300E, there is a rectangular 3 1/2" by 4 1/2" hole in the metal of the shelf between the center brake light and the first aid kit. You can see the bottom of the shelf lining material. With judicious cutting it should be possible to cut a 4 1/2" wide by ~ 2" hole that would be hidden by the first aid kit lid. Leave out the kit, and the hand opening on the lid at the front should be about the same size. Instant hole with minimal fuss. I personally would do like Brian and Yal suggested and dump the rear speakers instead, but this gives you an alternative. Good luck.

I kept rear speakers in my 500E as I often have rear seat passengers. So, I cut the hole that JCE proposed and it works just fine.

I too was concerned about road noise coming through, so I Dynamatted the entire trunk. It's as quiet as can be now; Dynamat's good stuff.

Yup...Dynamat works great. Also can be worth using carpet underlay in places to simply absorb (as a barrier) rather than damp the resonance.

Quiet cars anyway!

Bri

Actually, with the w123's if you take out the first aid kit and its plastic holder, there's no carpeting or anything. Also, it does make a world of difference. Good job on the 4's - i've noticed that the mids sound great in the factory spot, reflecting off the windshield. Make sure you aim the tweeters (if possible) off the windshield, as it creates a lot of coloration and harshness.
PS - focal polyflex coaxials are $100, and utopia 7" midbasses are 200 at http://www.zalytron.com - focal is getting more affordable :)
Good luck with that sub - nothing beats the look you get when people hear a booming w123 :)