Bose rear sub woofer wiring?

Hey all, my current project is to sort out the very rubbish sound in my C4S with Bose from 2002 but I need some help with the sun upgrade. So far I've stripped the Bose amps (one on the fuel tank, one by the spare wheel), installed a new 4 channel amp where the CD player was for the front and rear upgraded speakers. I've also upgraded the door speakers and wired them into the 2nd amp on the fuel tank, where the Bose Additional Am was. So far so good, aside from some resonance from the door speakers I need to solve. However, now I'm upgrading the rear sub. It's never made a noise so I want to check the connections. I believe the sub is wired from the white / white +red wires that come through to the "additional amplifier" which used to be on top of the fuel tank. There are 2 pairs of twisted wires, both white / white +red. At the sub end, there's only 1 wire, white / white + brown. The wiring diagram I've found shows 2 pairs of wires labelled simply " Sub +" and "sub -" for both pairs. This suggests there's something else in the system that's taking the 2 pairs of Sub wires from the front amp and putting out the 1 single pair to the actual sub. I can try wiring the 2 pairs into the amp but I don't want to blow something in the car, or more likely, not get any sound as something has already blown, hence no sound from the existing sub. So my question, does anyone know the routing for the wiring and whether there's anything else between the front sub and the woofer itself? And if so, where is it so that I can bypass it? Thanks.

I've used those wires. You can get into them by the spare wheel and they run to the rear shelf, just bleep them out to make sure they are correct. Mine are wired direct to the amp and speakers, saves running wires all the way to the back. You are correct, they are white in the frunk and brown in the back, but they worked fine with no issues.

Thanks Sim. Any ideas why there are 2 pairs in the front and only 1 in the back? How did you wire them into your amp? As 1 channel in parallel or 1 channel in series or 2 separate channels?

I don't. Mine was already ripped out, but when I changed the headunit and speakers I was tracing wires and checking continuity, I didn't notice two pairs connected to the sub, I just noticed that some original wiring was used and the colours. I'm not near the car so can't check.

I've now wired the door and sub speakers into a 4 channel amp. No sound from the sub but the door speakers are working, so I know the amp should be good. Its a new amp so I'd hope so too! I've checked there's continuity from both pairs of sub wires in the front to the plug in the back of the car. I've wired each pair into its own channel from the amp. I've replaced the speakers in the sub too so they should be good. I'm now at a loss of what to do. There's got to be something wrong between the front wires and the sub at the back. The fact that the 4 wires converge somewhere tells me that's the most likely place to investigate, however I don't know where that might be. I'll put out a message on Rennlist to see what they might know.

On your amp, are you using a pre out or filtering the signal from radio outputs? Or using one of the front/rear pre outs for the sub? Either way, needs to be configured correctly. My amp had various modes depending on the source for the low frequencies. On my android I used 3 pre outs, front, rear and sub. Sub required a splitter as it was a single wire. If you have continuity from amp to sub and it's configured correctly, you need to check your radio output. Then try a known working signal from the other amp to check your amp is working.

A few questions there: - Low voltage signal from the amp, 2 channels via RCA cables. Splitter to create 2 pairs of cables, one feeding each amp - Amp is configured for 2 channel input and is working. I've checked the input by feeding it to channels 3 and 4 as well, no change. I'm going to use a speaker popper (AA battery and some wires) to check the signal again to the amp from the front wiring. Something is definitely borked here, its weird I'm getting nothing to the sub

Don't want to state the obvious, but you have got it on lo-pass for the sub output? Obviously I don't know what amp you have.

Yup, but even if it wasn't I'd expect some noise from the sub speakers. Its 2 speakers of 5.25", not a 12" monster in the Bose box

I upgraded the speakers and amp in my 996TT few months ago and kept the Bose sub on the parcel shelf. It took me sometime to figure out the which wires to use as the M680 Bose 5000 wiring diagram colours did not match what I had in my car. I believe the Bose sub-woofer speakers in the rear are wired in parallel from factory and are rated at 1ohm impedance. I opened up the sub enclosure and re-wired them in series to increase the impedance to 2ohms in order to match what my amp (audison Forza) can handle. I took some pics today, in my setup, I used Brown(+) and Red-white(-).Hope this helps.