AUXILIARY BATTERY MALFUNCTION AFTER JBL 4 INCH SPEAKER INSTAL

[Mercboi2002]

So my mum has a c200 w205, last month I installed Jbl 4 inch speakers. I had to cut out the original Speaker out of its moulding which included this little capacitor. Didn’t think anything of it as it was connected to the Oem speaker. So I did that. Screwed the jobless speaker into the ring of the oem speaker moulding. Soldered the wires to the cable that was connected to the oem speaker and popped her into the doo trim. I only replaced the two front ones. I used the original cinjected cable and everything was fine. The car had better sound. The sub surprisingly had more bass, maybe because my speakers were using less voltage?. Maybe something To do with the magnet? Anyway. Couple weeks go past and then auxiliary battery malfunction popped up. Everything worked fine. But just yesterdsy my mum said the car was beeping and it was turning the music down. Can someome help me?!?

 

[John]

That capacitor would have been cutting off the lower frequencies to save the OEM speaker from being blown at higher volumes.

I would expect a 4" / 10cm decent aftermarket speaker to be able to go down to probably around 80Hz, which is why you can hear more bass now.

As long as they are not driven too hard / loud, they should be OK I would think.

The replacement speakers may well have a larger magnet on the back too as the tat MB fit as standard into their cars is made from old fag packets and bird shyte (it seems). So that will be improving the bass-ability of the speakers too as the cone will have more "throw".

With regard to the issues you are now getting, I suspect you have two separate issues.

The first issue is a bit of a show-stopper. The output from the OEM amp (to the speakers) can detect if the load impedances are not right (as the OEM speakers can use really odd impedances and not the usual 4 ohm you expect for car audio).

It will then reign in the output from the OEM amp to avoid damaging the speakers or the amp. That's probably what your mum is hearing.

To get around this, you would typically fit a "load sensing adapter" but this is normally fitted inline between the OEM amp and aftermarket car audio processor (e.g. JL Audio FIX 82). This aftermarket car audio processor is usually then connected to an aftermarket amp and onto the speakers.

Or, you need to use aftermarket speakers with the identical load impedance, but you will have a job finding out what the load impedance is of the speakers you took out, and then have a job finding aftermarket speakers with the same impedance. I'm not sure why they do this but it's probably related to a better bottom line somehow.

The second issue is I suspect you may have a duff auxiliary battery / capacitor. See here: W205 Auxillary battery charging. | Engine

In summary, if you have a capacitor, I understand the early ones are known to be shyte, so it can just be replaced.

If you have a proper aux battery, I would buy a decent battery charger (e.g. Maypole 7428) and run it on charge overnight to see what it can do. If the battery cannot be improved, it may need to be replaced.

Or you could just try replacing it anyway but charging it is cheaper to start with!

I've heard the main battery and aux battery should be replaced at the same time but I doubt this happens in most cases and I can't see why it matters too much as the batteries are not linked in series and are separated by contact switches.