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2002 E320 4Matic
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Discussion Starter #1
I am posting this just in case it is useful information for someone else. And in case anyone can explain a puzzle.
My from left (dash) speaker stopped working, in my 1992 300E sedan. Because I had earlier had some work done on my seat control switch, and the technician who did the work had taken apart all the associated wiring, and because I believed that the dash speaker is connected to the door speaker (that is, they are wired in parallel to the same amplifier output), I assumed that the speaker connection had been disturbed. So when my car was in the shop for another reason, I asked my regular mechanic (not an MB dealer) to check the wiring and try to find out why the speaker did not work.

The mechanic determined that it was the speaker itself that was at fault, and ordered a new one from MB. He was told that the original speaker had been replaced. The old speaker is marked with part number 1248202802.
The suggested replacement has part number A1248203502.

The two speakers are not identical. The original speaker has two leads into it, with two different types of electrical connectors. The replacement speaker has only one lead. (When I say "lead," I mean a 2-conductor cable.) (If I can figure out how to do it, I may try to upload a photo of the old speaker later.)

So this is a puzzle, for two reasons. First, it is puzzling because the wiring diagram in the service manual does not indicate two leads. So why two leads, and what is the difference in the incoming signals? Where do the two different signals come from?
Second, one wonders what difference it makes when the replacement speaker has only one lead. The door speaker still works, so apparently the second lead did not affect that. And it was not apparent when listening to the new speaker that it was markedly different from the right front speaker, which is (presumedly) still the original design.
The original speaker has two cones. The outer cone (4 inches in diameter, a midrange speaker, I assume) is fed from a lead that passes through a capacitor. The inner cone (1-3/4" diameter) appears to have its own coil, fed from the other lead. This arrangement strikes me as odd. My recollection is that a capacitor is used to filter out low frequencies from a tweeter, to protect it from damage if it were exposed to frequencies it cannot handle. But this speaker appears to be set up the opposite way: the filter is on the wider, heavier speaker. But of course, it is possible there is another filter upstream from this speaker that protects the inner cone, which I am calling the tweeter. But maybe the design simply isolates the two speaker coils.
I got the old speaker from the mechanic and tested it. The tweeter seemed to work, but the midrange did not. but when I bypassed the capacitor, the midrange would work. So the failure was apparently in the capacitor.
So, maybe not very important, but possibly useful for someone else who needs to replace a dash speaker. And maybe someone who knows why the old speaker had two leads will fill us in...
 

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97 SL500, 2003 Suburban, 88 300TE , 2005 E500 Wagon
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I believe the second set of leads was used for the factory installed phone. I'm not positive, but I've never had an issue replacing w124 speakers with standard drivers.

Todd
 

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2002 E320 4Matic
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Discussion Starter #3
mystery solved, dash speaker for 1992 300E

I believe that Todd is correct. The second lead on the front left dash speaker is for the telephone. Although my car did not have a phone (so far as I know), the cars were prewired for the phone.
The connection for the phone is shown in the wiring diagram for the phone in the Electrical Troubleshooting Manual. It was fed from the phone electronics, so it had to be electrically separate from the radio output. Only the front left speaker was used, which makes sense, as it is the one closest to the driver (in US cars).
Using a separate coil on the same speaker avoided having to install a separate speaker for the phone. Probably saved cost as well as real estate.
Presumably Mercedes no longer supplies that type of speaker because the phones of that era are obsolescent and no longer in use.
So anyone else who replaces that speaker can ignore the second connection (unless by chance they still need a telephone connection).
 
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