So I am installing a subwoofer for the first time in this car(08 g35x) and I have found wiring diagrams but I want to be sure of myself before I go tapping into wires.

So if I'm using a 1 channel setup I should tap into the wires for the already existing sub which is 16 and 17 as highlighted in yellow above. Does anyone know what the wire colors are I can't find a key or anything?

However, if I'm using 2 channel it would be better to tap into the subs in the front doors correct? also again can someone help with wire colors?

 

 

I still find these FSMs hard to decode...

I believe you have a rear shelf-mounted, self-powered "mono" woofer which is part of your Bose w/o NAV rig. Look in that book at connector B46 and you'll see signal + / -, amp on, battery and ground. If you are intending to simply replace or upgrade that rear shelf mono sub then that would be a great place to tap into it. The Bose amp has already summed L&R to mono and (I suspect) done the crossover for you so all you should need to do is add a mono amp and great speaker. Since the stock unit is also self-powered, that means the signal passing through the Bose amp has not been amplified so that's a clean way to do it.

I believe plug B41 are the inputs to the Bose amp and B42 are the outputs. So if you are trying to upgrade the door woofers and do stereo subs - then the cleanest place to tap that L&R signal might be at the input side of the Bose amp before it's amplified. Make sense? The Head unit would still control the volume, balance, tone, etc. but you could set the amp's level to balance the system as you chose. You would need to "low-pass" that signal for your subs if you tapped and there and it would be following the front door speakers levels - if that's what you're trying to do. If you want to tap it after the Bose amp (and already low-pass filtered) then you can use the outputs you highlighted on plug B42 above. That would be sending speaker level into your new amp so adjust accordingly,

 

I'm installing a box in the trunk so its not replacing the Mono, would you recommend tapping before or after the low pass filter whats the difference of tapping before or after ?

 

I'm not the audio system expert in here so wait for some better advice.

But I will suggest that if you are doing a trunk mounted "addition" to your system I don't think there'd be any benefit in going stereo. Because you won't be able to hear the left and right imaging from inside the trunk. Bass frequencies move a lot of air and tend to sound mono anyway. So in your case I would think the simplest place to grab audio, and "amp on" signal would be that B46 connector off the Bose amp. You would probably need to run new "battery +" and ground wires because the Bose wiring harness will only be rated to carry enough current on that connector for the stock woofer amp. Especially if you plan to leave the stock woofer in place and share those connections. A new amp would likely draw more current and need its own of power and ground connections.

Again, there are many more knowledgeable folks in here so standby for better info.

 

On an 08 sedan, the remote power you're looking for is light grey.

The connector is brown in color.

It's the middle connector, on trunk preamp.