I'm getting a Sony CDX-GT310 (http://www.crutchfield.com/S-SfJpyOXTFMG/App/Product/Item/Main.aspx?i=158gt310) Sony is selling them refurbished for $69.95... I know it's not the best, but it has pre-amp outs and everything else I am looking for.. So my selection in head-unit's aside...

I ordered the necessary harness from Autoleads and the antenna adapter.

The Russian VIN decoder gives me the following audio-related output:

• Becker Radio Mexico cassette, full stereo, electronic (с 01.04.1980 по 30.11.1990)
• Becker Radio Grand Prix TR with remote control and automatic antenna (с 01.04.1964 по 31.05.1977)
• radio MB-Exquisit - USA (с 01.07.1992)
• active bass loudspeaker system (с 01.10.1989)

Does my car have 2 ohm or 4 ohm speakers?

Does it have an external/two-piece amp?

I chose the Sony based on price and the fact it has pre-outs... I figured I'd end up needing to use those but wasn't quite sure.

Switchable Preamp Outputs: The CDX-GT310 contains one pair of RCA preamp outputs that can be set for the rear channels or for subwoofer operation. When set to subwoofer, the output becomes non-fading and a low pass filter is activated with a selectable cut-off frequency of 125Hz, 78Hz, or Off.

The Preamp voltage is 2 volts.

As for the built-in amp:

• CEA-2006 compliant and rated at 17 watts RMS x 4 channels at 4 Ohms and 1% THD.
• Unit is rated at 23.2 watts per channel minimum continuous average power into 4 ohms, 4 channels driven from 20 Hz to 20 kHz with no more than 5% THD.
• Peak power is rated at 52 watts per channel.

What do I need to make this work...? Am I using the pre-outs? I'd prefer not to rewire all of my speakers...

Thanks,
Jeff

why not just pull the rear speaker and see what ohm rating it is ?

and as far as the external amp .. i doubt its gonna be usable unless you splice into the wiring.. when i opened mine up for replacement it was a wire/plug mess .. all the extra little bs was a pain in the ass.. so i took the time and wired it separately .. that way if someone wanted to put original stereo back in they could ..and my new head unit would have a truly clean install

That's my goal if it takes under 5 hours of time... Did you follow a howto... also, where would my amp be located and what kind of tools/materials does it entail?

Thanks for the quick reply

I just installed a new Sony headunit into my 1993 124 sedan last weekend. It had the same active bass system as your car. I got good news for you, and I got bad news for you. The good news is, it can be done, and the system sounds surprisingly good in the end. The bad news is, it's a lot of work. More time than money, but much work in the end.

First, what you have now is the infamous Becker 1432 two piece radio. Apart from the head unit, there is a tuner/amp combination in the trunk. It's mounted behind the mouse fur trunk panel on the right hand (passenger) side. The built in amp is a two channel amp that is wired to the fader switch in the console. From there dash and rear deck speakers are driven. The speakers are ~6 ohms - I measured them.

In addition, there is an active bass amp in the trunk. It drives the two 6.5" speakers in the doors. The amp uses speaker level inputs, so you won't need the pre-amp outs on the head unit. The amp is also located in the right hand side of the trunk.

I found it faster and easier to run new wiring to each of the dash and rear deck speakers. I'm not even sure there is anywhere you can get access to the wiring for all four speakers. If so, it's somewhere near the fader switch. My new install bypasses the fader switch, each of the four dash/deck speakers is wired directly to the head unit. You'll need to do the same to take advantage of the four channel amp in the new head unit.

To drive the door speakers, I retained the stock active bass amp in the trunk. Because it uses speaker level inputs, I tapped into the rear speakers to drive it. The amp also needs a +12v signal to tell it to turn on. For this, I ran a new wire from the head unit back to the trunk. The Sony I purchased had a lead for activating remote amps - I'm sure yours does to.

You'll need to purchase a 12' long antenna lead extension; they're about 10 bucks. The current antenna lead goes to the tuner/amp in the right hand side of the trunk. From there you need to run it up to the new head unit.

This is a tough install. You really need access to the wiring diagram to get it done right.

- JimY

Thanks for the detailed reply... unfortunately I have the Becker 1492... which I can't believe I didn't include in my post!! (Sorry) does anyone know if I'll have to go through the same torture?

I had a 1993 300E (3.2) "E320", and I believe I had the same setup.

My system ran off of 2 ohms of resistance, and all current head units / speakers use 4 ohms, so I had a shop rewire the whole deal. It cost me several hundred dollars in labor alone, but I installed a Nakamichi head unit with a Nakamichi amp, all new Polk speakers, a subwoofer in the trunk, along with an iPod jack snaked into the little box beneath the arm rest.

__________________
Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

Hm... does anyone have experience with the 1492?

My bad. I assumed the 1432 was used for the remainder of the model 124 run. It appears the 1432 was used for 1991-1993, and the 1492 from 1994-1995.

I've got the 124 shop manual on CD, so I checked the wiring diagram for 1994. Look's like you've got it easy kid.

The 1492 is a single piece radio with outputs for four speakers. Everything you need to wire up the Sony is right there in the dash. Your system does have a remote power amplifier (presumably in the trunk) for the door speakers, but you can easily retain this amp.

On the back your Becker has an electrical plug with four wire pairs. These are the speaker outputs. By color, they are:
- Grey & grey/red: left front
- Brown & brown/red: right front
- Black & black/red: left rear
- White & white/red: right rear

The amp for the door speakers takes its input from the front speakers. So by reusing the existing wiring, you get the amp inputs for free.

There's a second multiwire connector on the Becker. I've included the pin numbers, you can read them off the connector - some of the wires have the same color scheme. Note that some of the wires may be inside a plastic sheath, and the wire coloring is different than the sheath coloring.

- Red, pin 4: Either hot all the time, or hot when the key is on, can't tell.
- Red/yellow, pin 7: Either hot all the time, or hot when the key is on, can't tell.
- Brown, pin 8: Ground.
- Blue/white, pin 6: Dash light illumination. Can be used to trigger display dimming, if your head unit supports it.
- Blue/white, pin 3: input from cellular telephone, mutes audio when triggered.
- Black/grey, pin 1: Speed input for speed sensitive volume control. I hate this feature.
- Black, pin 5: Radio antenna trigger.

There is one other single wire connected to the unit.
- Black wire inside a brown sheath: Another ground. Don't know why two are needed?

One problem you might have. It looks like the signal to activate the amp for the door speakers also comes from the power antenna up signal. This works fine on the Becker, it raises the antenna whenever it is switched on. On my Sony headunit, it raises the antenna only when in tuner mode, for other sources it lowers the antenna. The Sony also has separate antenna and amp triggers. So you might have to run a new trigger wire to the trunk to activate the amp. If you want to do this, the amp turn on signal is on pin 7 of the amp connector, it's a black wire.

This oughta get you going, have fun.

- JimY

Thanks, you guys have been very helpful.

So I have 4 ohm speakers?

Just to double check you're saying my door speakers are powered by an amp in the trunk, but they take the input from the front speakers... so I'm not using my pre-amp output for anything?

I have a basic understanding of relays and should be able to figure out the antenna/amp situation, I never use the radio... so it's less of an issue.

I have the pin out/wiring diagram from Becker, so if my speakers are 4 ohms (I'll pull one of the trunk ones today) then it sounds like I do have it easy!

I guess it's hard to say, but is this unit underpowered to drive the stock speakers?

Also, as far as the active bass kicking in, I think it takes a reading from the HAL effect sensor... that apparently detects speed and adjusts the volume accordingly... apparently alot of aftermarket head units have this built in?...

The part # for my rear speakers are: 124 820 41 02

I didn't see any indication of whether they are 2 or 4 ohms.

The dash speakers are more like 6 ohms. I didn't directly measure the trunk speakers, but expect they are 4 or 6 ohms. I wouldn't bother pulling them, don't think it's worth it. Just hook 'em up to the Sony and go. If you insist on checking, don't bother pulling the speaker. Just check the speaker leads while you have the head unit out of the car. Much less work!

The Sony I installed has the same amplifier specifications as what you initially posted. It is doing fine driving the four speakers. No smoke yet The head unit supplies as much power as you want to feed to these speakers. Any more power and I think you'd just roast the stock speakers. It will play as loud as you need it to play, though maybe not as loud as you want it to play.

You don't need the pre-amp outs for anything, that is correct.

If your Sony is like mine, it will have one lead used for triggering a power antenna, and another for triggering a remote amp. The hardest part of your install will be to run a wire from this remote amp trigger to the back of the car and connecting it up to the amp. It can be done, but involves a bit more disassembly than just replacing the head unit.

You'll be surprised how good the system sounds when it's done. I didn't expect much just because it was so awful with the original Becker. But it's actually pretty decent now.

The active bass doesn't have anything to do with the speed sensor; there's no connection between the speed input and the active bass amplifier. The speed signal was used to trigger the original radio to turn the volume up a step at certain speeds. My newer MB has this and it really annoys the snot out of me. The volume goes up at 35MPH, and again at 65MPH. Then down at 55 and 25, or so.

- JimY

Can I reuse the telefone antenna wire for a trigger with a common ground of sorts? ...

I don't understand what you are asking.

You know, it occurs to me that you can use the new Sony headunit's external amp trigger wire for the car's antenna up signal. If you do this, the antenna will be up anytime the Sony is switched on. But you won't have to mess with any wiring for the active bass amp in the trunk - it will just work automagically. Can save yourself 2-3 hours work disassembling the interior, removing the backseat, removing the trunk lining, etc. by using this trick.

- JimY

So the antenna trigger also turns on the active bass amp? Awesome tip...

I was asking if I could use the antenna lead for the car phone to trigger the amp (disconnecting it from the hirschmann of course)

JimY, that is GREAT info about the 1432 setup (1991-1993). I am trying to figure out how to upgrade the deck my 1993 300D, and my initial research was indicating that I might need to run new wires to front & rear speakers, plus an antenna lead from the trunk to the new radio. Your post confirmed all that - thanks! What I was not sure of was the door speaker setup. Do you know which wire colors are used for this? Also, can you tell me which page(s) in the ETM have the correct schematics? There are several different schematics shown and I still can't figure out which one is applicable to my 1993.


Jeff (and others), if you want to upgrade a 1492 (1994/95), or most any other 1981-1990 Becker... there is a drop-in AM/FM/CD replacement available from Becker, complete with a wiring harness adapter - total plug & play. Only downside is the cost, about $450 or so brand new. A photo is at this link. It can accept an iPod (and cell phone) input, which is cool. The Porsche CDR-220 is nearly identical, available for ~$200 or so on eBay... only problem is the CDR-220 display angle is on-adjustable, so it's a little hard to read the display. One nice thing is that the speed-senstive volume is adjustable, and can be switched off if desired.


For installing an aftermarket radio in a 1994/95 model that originally came with a 1492, you can buy an aftermarket harness that plugs into the factory female connector, so you don't need to cut any of the factory wires... this allows easy re-installation of the stock deck, if you sell the car in the future, etc. Most decent stereo shops should be able to source this cable (?), or you can get one on eBay (like this, for example).


BTW, here is a link to the various years/models of Becker radios. Click on your year/model, and the next menu will tell you what wiring harness, amps, upgrade options, etc are available:
http://www.beckerautosound.com/mercedes_year_model.html

__________________
Dave
Boise, ID
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