I'm cheap, lazy and have tin ears so all I needed was a little more bass to be happy with the factory speakers in my 87 300D. The answer came by way of a used Subaru powered subwoofer. I'm not sure what model Subaru it came from but I understand most models use this sub under the driver seat, or under the passenger seat if the driver seat is motorized. They're all over eBay. This one cost me something like $60.

Why a Subaru subwoofer? It's the smallest one I could find and the only one I could find for under $100. The Kenwood units are way too big to fit under the first aid kit cover, let alone under the front seats. In fact I can't imagine anything fitting under the front seats. There's a discontinued JVC unit (CS-BB2, I memorized the model number from months of eBay searches) and a Clarion unit (SRV314, I think) that might work, but I think the Subaru unit is the least tall and it barely fits under the first aid kit cover. More on this later.

There really isn't much to installing it in the rear deck. First thing I did is remove the first aid kit cover. The front clips are screwed into the deck, the rear clips have a slide tab to release them from the deck. There's a little more detail on this in a recent post of mine in the Diesel Discussion forum. With the rear clips out, there are two convenient holes for wiring. The base of the sub is wider than the rear deck trough. I located a rear deck in better shape than mine for $10! With a replacement deck safely in the garage so I car return the car to its orginal state, I took a Dremel to the aft wall of the trough between the cover clip holes. I removed the section of deck board and insulation between the lower edge of the clip holes and the floor of the trough and between the outer edges of the clip holes. The edge of the sub fits perfectly in the cutout. And now it sits flatly on the floor of the trough.

The wiring is also quite simple. The sub takes line level signals. The rear speaker wires are right there so the most difficult thing was to get myself belly up in the trunk. The sub doesn't seem to have a problem with the common ground setup MB uses. I added a relay for power. The relay engages when the factory antenna gets a signal from the stereo. Fortunately my Sony stereo uses the antenna signal as a remote amp signal as well so it triggers the antenna anytime the stereo is powered, not just when set to radio. Anyway, the relay is powered when the antenna is powered but power itself comes from the antenna's power source, not the stereo signal. I've blown enough stereo antenna circuits to know the milliamp trip signal can't power even the wimpiest amplifier or CD changer.

The most difficult part of all this was modifying the first aid kit cover to hide the mess. I trimmed so much of the ribbing out of the cover that it no longer holds its shape. Well that and the big hole I cut so the cover sits flush on the deck as it did before. Even after removing all the ribbing over the sub there was a gap between the cover and the trough. I took the Dremel and cut a hole the size of the sub so the cover slips over the sub, and of course there's a hole for sound to go through. Fortunately the sub is slim enough that it sits below the top plane of the cover. I got a yard of light gray speaker grill cloth (shipping cost 50 cents more than the material!) in a reasonably close shade. Certainly a better match than I could have hoped for (and now you know why I like light gray interiors). I couldn't decide on what adhesive would work best. The stuff that bonds the deck fabric to the cover is pretty good but what the heck is it? And if MB sells it, it probably comes in 5 gallon buckets. As I set to try a tube of 3M maximum strength glue I happen to have, I noticed a very convenient 4mm channel around the rim of the cover. The original fabric tucks into the channel taking about half the thickness. So I dug out a spool of 18 gauge wire and used that to friction fit the speaker cloth just as you'd do putting new screen on your patio slider. It was so easy, I had to share it.

So I'm done. The cut-out in the cover and the weight of the cover keep it in place. If it somehow jumps out of place over ruts and bumps, I'll use some double sided tape to keep it on the sub.

Here are some pictures -





The crease in the finger notch on the forward edge of the cover is there because the channel doesn't extend into the notch. Or maybe it did but I had to trim the material so the cover sits flush. At any rate, I have to figure out how to tension the speaker cloth so there isn't a crease -





You can see the ends of the black 18 gauge wire I used to hold the speaker cloth -



I keep the factory original first aid kit at home. I'm pretty sure my next cut will heal just as quickly on its own as with 20 year old salve that's been baking in Texas and California sunshine.

Sixto
87 300D

Very nice, almost looks factory! I might consider something like that myself.

I dig it.

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
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Six others from BMW, GM, and Ford.

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