91 W124 Active Bass System Question

[bowman]

Hello Everyone,

I have a stereo system question.

I put an Alpine Head Unit into my w124 wagon, replacing the Becker Original. I installed it initially with just the dash speakers running to the head unit. I obviously sounded a bit thin. So yesterday, I decided to try and wire in the rear door speakers and the front door subwoofers (mid-bass) to supplement the sound. After eliminating the factory fader unit, I succeeded in wiring in the rear door speakers as the rear speaker off the head unit.

I understand from other posts on this forum that the subs in the front doors are powered by an amp in the rear cargo area. (my amp is dead)

My question is how can I wire in the front door subs from the Alpine? without the amp in the back. Can I wire them directly into the head unit?

There are 8 wires coming to the old fader but I could not get the front door speakers to do anything from those wires? Not a peep or a crackle.

I think I would be satisfied with the sound if the front door subs were working instead of the rear door 4.5's since the Alpine has a built-in amplifier?

Any advise? I don't want to spend much money and don't want to buy an amp, but do have all the tools to rig it all up if it's possible.

Thanks for any help and if anyone has a schematic for a 91 Active Bass System, could you post it here?

[bowman]

So I just got in the car and turned the bass up on the Alpine head unit and lo and behold the amp and subwoofers in the front doors kicked in (intermittently).

Now I really don't have a clue what is going on!

I have removed the factory fader unit and used only two of the 8 wires coming out of that to power the rear door speakers. So what in the h*ll is powering those front door subs?

Do anybody have a full schematic for the original Becker/ amp in the back / speaker set-up?

How is that amp linked through the new Alpine? the Antenna Power-up lead?

[JohnM.]

Hi,

I have the same stock, "active" bass system in my 300E. I also have an aftermarket Pioneer head unit, everything is amp'd thru a 4 channel amp mounted in the trunk, with stock wiring. But I originally was just running off the internal HU amp for the first few months.

BUT. Regardless. If you tap into the stock wiring right behind the head unit, you should be able to find the left and right channels for the front speakers. These connections are before the fader, so if you tap in here, you are bypassing the fader for sure. Now the front dash and door speakers (L+R) are paired together, so you will end up with one +/- for the 2 left side speakers and one +/- for the right side speakers. I like to use a 9 volt battery to figure out which side is which. I have had my stereo wired like this for over 2 years with absolutely no problems. Even when I installed the power amp, there were no issues at all. People are amazed that all my speakers are still the stock 1991 paper coned units!

May be slightly different for the wagon, since you have the rear door panel speakers. But you should be able to tap all of the speaker connections right behind the HU, without having to tap thru the fader, which makes it sound like CRAP! Good luck. I have the stock wiring diagram for the active bass system in the 300E sedan somewhere, I will post it if I find it.

[RichMason]

I have the same system and am getting some strange deep clicks through the stereo. I need to go through the wiring a diagnose but I don't have a clue where the amp is so I can check its connections. Is it in the dash or footwell on the passenger side? I believe that I found a power lead for it when I installed my new head unit and spliced in the power cable for the antenna. Is this the correct signal or does it use something else?

Many thanks,
Rich

[ds190]

The door mid bass speakers (2 ohm) are driven by the trunk amp. That amp gets a high impedance signal from the fader at one of the rear speaker leads. If the amp is not on and you test at the fader, no you will not hear a pop or whatever out of the mid bass speaker.

All you need to do to replace the Becker 1432 is:
1. connect front speakers to front HU out. Find correct wires from fronts, cut them before they get to fader, and wire to the HU.
2. connect fader to HU to drive rear speakers and door speakers. Just connect the leads out of the old radio going to the fader to the rear channel of your HU. Set the console fader to full rear.
3. the amp on lead is not the same as the power antenna lead. Find the correct lead to the amp and connect it to the amp on lead from your HU.

Done- your HU drives the front and rear speakers, and the factory amp drives the mid bass door speakers.

[olasdeplata]

I just got a W124 sedan 1989 with documented 71k miles that I am delighted I was able to find, for my son's 16th birthday. With him, I have been fixing and upgrading small things, and the stereo in next.

I am replacing OEM speakers with Focal coaxials, 4" in the front, 5 1/4 in the rear, and two Kicker 8" free air subs underneath the headrests in the rear deck powered by a Harman Kardon CA260 placed in the trunk.

Now: How do I know if I have the optional Becker amp in the system powering the OEM front and rears? And if I do, does anyone have a picture of the location?

The center console fader control works and the head unit has been replaced by a Kenwood CD/MP3. The front and rear speaker are Mercedes OEM coaxials. Also, I heard that aftermarket head units will burn in no time the fader control... and it should be bypassed when upgraded.

Thank you for any advice, I am not familiar with this car yet.
mariano