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  #1  
Old 09-09-2012, 10:04 PM
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Location: MA
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92 400e speaker wiring (originally had 1432)

Trying to correct the botched job the previous owner did with an aftermarket head unit on a 400E (orig radio would have been becker 1432 with amps in trunk and Dash, door and rear speakers).

Anyway powereing the fronts is obvious - you can see the speaker connectors with the head unit out - wire in to FR and FL of the head unit.

The rears and doors are the question. I can run lines front he head unit RR and LR tot he rear deck speakers. That leaves the doors?

How do you power the doors????

The head unit (sony CDX-GT52W shows mono subwoofer outputs on the diagram I pulled from the web - I could use those for the doors but what leads? The speaker outputs from the amps look like 2 sets from each amp (I know the factory amps would power R and L - NOT F and R) the black and yellow are obvious and go the the rear deck - does the grey set go to both the F and doors? If so would runing the sub to that set of leads power just the doors (fronts are now unplugged from harness)?

thanks for the help.
Paul

BTW I have a set of the 1432 amps if that would be a better solution - But I'm not sure what the inputs are to the 1432 amps (colors) and if they take preamp (which the head unit has) or line, searching has me confused.

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  #2  
Old 09-12-2012, 02:30 PM
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Maybe finding some pieces of the puzzle - there is a good post with links to the audio schematics from the manual here;
Pinout for Becker Amp - Benzworld.org - Mercedes-Benz Discussion Forum

Post 4 has links to the schematics which are also on the factory CD's that I have (once I found the correct part).

So from my reading of the diagram I should be able to feed the rear speaker output from the head unit to the right and left anps (pin 9 and either pin 5 or 7 as they are bridged). This bypasses the fader.

Anyone know if I should use the powered output or preamp output?
Anyone know if this will supply anything to the door speakers?

The head unit does not use common grounds on the speakers , the car diagram splits grounds L and R so it may be OK (the head unit only warns agains cars that share common ground between left and right.

Also as has been noted elswhere it looks like if I have power to the antenna I should have power to the amps (pin 8), I can always run the remote amp lead from teh head unit if necessary - I put the extra wires in.

So any advise? Failing any answers I'll be experimenting this weekend.

Paul
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  #3  
Old 09-12-2012, 03:20 PM
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Location: Plano, TX
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I made a similar upgrade on my 1993 300E, using a Sony head unit.

The trunk mounted amp for the door speakers uses a speaker level input. Once you identify the pin inputs to the amp, just tap them into either the front or rear speaker runs. I don't recall whether MB used the front or rear to drive the door subs; probably doesn't matter in practice.

I ended up running new wiring from the head unit to each of the four dash/deck speakers. It was simply easier and faster than reverse engineering the existing wiring and then troubleshooting the result.

You'll also need a remote turn-on signal for the trunk amp. Any modern head unit should supply such a signal. I recycled an existing wire run from the old Becker head unit back to the trunk to implement this function.

The setup sounded surprisingly good once installed. It was a big improvement over anything that ever came out of the Becker.
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  #4  
Old 09-12-2012, 04:00 PM
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Thanks - I will report back once I get to it this weekend. When I had the carpeting out I ran 4 pairs of ~14ga wire plus one small ribbon I had around (4 or 5 strand probably ~20ga which should be fine for the low level amp turn on).

Tonight's task is to repair the ground wires the mice chewed on under the center console.

thanks again
Paul
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  #5  
Old 09-13-2012, 10:47 PM
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Good job getting rid of the horrid 1432.

Like he said, speaker level input to drive door subs, and MB tapped a rear speaker for that signal in the console fader.
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  #6  
Old 09-22-2012, 11:05 AM
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Current status - from the mercedes wiring diagram of the 1432 it looks like the amps take line input. So, wired it up to the line out from the headunt - wired to the 4 lines (L & R) that go to the fader, routed the amp on line from the head unit to the car harness, and... it works fader and all. HOWEVER the output is pathetic. Turning the head unit to max vol gives a reasonable stationary car not running level.

This confirms what people have said that the becker amps can take speaker level inputs (also confirms that line level is not always the same).

Next is to wire to the speaker outputs of the head unit.

Paul
Update on 9/23 wired into speaker output, now things play at reasonable volume levels, mid volume on the Sony (15-16) is realy fairly loud. I know this is less desirable acousticaly as you are running the signal through the sony amp and the pre-amp outputs are more "pure" but its fine for now. No idea if using the speaker level outputs can damage the becker amps over the long term, doesn't really matter to me as if there is an issue at some point in the future I will buy a separate 4 channel amp. The nice thing for now is the original fader still works


Last edited by moruzzi; 09-23-2012 at 06:51 PM. Reason: adding new info.
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