Replacing door speaker wiring - R129

[gramey]

Originally it started off that the bass speaker in the passenger door would cut in and out and it was suspected it was the voice coil in the speaker. I replaced the bass speaker with a brand new Audison one but it was still cutting out. Then it was far more out than in and then mid speaker above the bass has cut out as well so I only have the dash tweeter.

I've just changed the head unit from a Halfords Sendai unit to a Mercedes Audio 10 (2nd hand obviously but from an audio refurbisher fully checked and working) as I wanted an original looking dash, not bothered too much about Bluetooth etc.

So having eliminated the possibility of it being the speaker or head unit a process of elimination says it must be the wiring to the speakers. So short story long is it feasible to attach a new length of wire to the old one at the speaker end and pull it through to the head unit, or vice versa, or will I have to strip out half the dash to feed the wires through, I don't really want to bodge it and just shove it under the carpet in the foot well.

 

[PHAB]

Hi Gramey,

I think your process of elimination has overlooked something...in the R129 there is actually an amplifier in the passenger footwell (assuming you do not have the bose setup without rear seats). It sounds very much like that is your culprit - unfortunately changing the head unit will have achieved nothing functional as its only used as a preamp in this setup....also tracing the wires back wont help either.

My advice - start with the amp!

 

[Bernie C]

Hi Gramey,

I think your process of elimination has overlooked something...in the R129 there is actually an amplifier in the passenger footwell (assuming you do not have the bose setup without rear seats). It sounds very much like that is your culprit - unfortunately changing the head unit will have achieved nothing functional as its only used as a preamp in this setup....also tracing the wires back wont help either.

My advice - start with the amp!

Had exactly the same issue - as Phab says start with the amp - mine had dry joints causing the cut outs - replaced it in the end with a second hand amp - worked perfectly since - it's a very straightforward job

 

[gramey]

Hi Gramey,

I think your process of elimination has overlooked something...in the R129 there is actually an amplifier in the passenger footwell (assuming you do not have the bose setup without rear seats). It sounds very much like that is your culprit - unfortunately changing the head unit will have achieved nothing functional as its only used as a preamp in this setup....also tracing the wires back wont help either.

My advice - start with the amp!

How do I find this, presumably it's under the carpet but on the floor or the bulkhead where you'd rest your feet?

 

[gramey]

Ok so a quick update, I got the door panel off and somebody had obviously been there before as half the clip holders had been pulled off the back of the door panel so I had to re-glue those. I replaced the wires from the connector block to the bass speaker and as close as I could get to the crossover as when I opened that I decided it was best leave well alone. As it turned out I could have saved myself the trouble of unsoldering the original connector block and soldering in new wires.

I connected the speakers back up and absolutely no difference, I reversed the pins between the speakers and presto the base speaker was working but now the mid range wasn't working. It appears that the crossover is knackered, I connected the speakers bypassing the crossover and both are now work although obviously there's no separation. Not sure about the amplifier previously mentioned as it's not immediately obvious that it has one, certainly the volume levels don't suggest the sound is being boosted?

I presume there's little chance of being able to buy just the crossover or a suitable aftermarket one that would fit in?

I also have a slight issue with the door panel not wanting to stay clipped in at the front, I'm not sure if it's the clips I got from the SL Shop or if something else is causing an issue. I took the panel off and checked everything and couldn't find any reason why it won't sit flush but there's tension only at the front for reason or reasons unknown?

 

[valleyforge]

How do I find this, presumably it's under the carpet but on the floor or the bulkhead where you'd rest your feet?

Hi,
Glad I found this thread as I have the same problem - intermittent cutting out of the lower bass speakers - both together - mainly out - have tried a different radio unit & that is exactly the same so its the wiring or this tricky little amp in the passenger (UK RHD ?) footwell. Tried to find it but no joy so far. Took the sill cover off, lots of nice cable runs but box of tricks. Took the speaker cover off & speakers look fine as car has had dry use only most of its life.
Have posted on the benzworld forum but state side cars seem to have the Bose unit instead of the rear seat. Under my rear seat is a rather forbidding computer looking thing with stickers on saying do not touch.

A little annoying problem but enjoying the challenge !
ps car is a 2000 yr sl280.

 

[gramey]

Unfortunately the budget is stretched at the moment as I'm having a new soft top fitted at the end of the month so for the time being my botch is going to have to do as there's no money left in the pot to completely replace the stereo. I much prefer the look of the Mercedes Audio 10 unit I've fit in place of the garish looking Halfords Sendai unit that was in there. I don't really miss the blue tooth as I can't be bothered to talk on the phone while I'm driving anyway. I can manage without the USB but it is rather annoying that it won't play CD-R discs.
I probably need to source a Mercedes Audio 30 or something similar so I can enjoy compilations again rather than having to keep swapping CD's. At some point in the future I'll change the speakers so I can get the separation back between the speakers but in the meantime at least I have music on both sides.

 

[valleyforge]

Hey Gramey thats a good trick - I'll try that if nothing else works. I have a fancy Sony unit with cd changer & tape player, very period and a great sound when it happens to work. + Great minds etc. - my hoods being replaced later this year too.

 

[gramey]

I had new front wings fitted two months ago so with the top being done at the end of the month there won't be any more major spending on the car this year other than routine servicing and any unforeseen occurrences.

 

[valleyforge]

Just a brief update - Found the amp - under the rear seat passenger side - under the carpet. Bought a pre-used item & hey presto, all works fine . Phew !

 

[silver50]

Just a brief update - Found the amp - under the rear seat passenger side - under the carpet. Bought a pre-used item & hey presto, all works fine . Phew !

I have recently been searching somewhat fruitlessly for front speaker wiring info. RHD 1999 SL320.

I can't understand there being a hidden amplifier especially if a new stereo has been fitted. How is the amp getting its's signal? I thought all non subwoofer/rear speaker R129's just had door speakers powered from the stereo itself.

I am searching to try and find out how the wiring splits to feed the upper and lower door speakers. Any info most welcome!