E70 Sub/Amp Install DIY (sort of)

[finagle69]

I've transplanted my JL 500/1v2 and 10w6v2 from my Infiniti G37S Coupe into my new-to-me '08 4.8i sport.

I'm used to car forums providing a wealth of knowledge for the do-it-yourselfer... but such is not the case at the few X forums. So I figured I'd contribuite.

I basically reused everything from the G to the X. Having the battery in the trunk makes is infinitely easier in the X. The most difficult part was wrapping my head around the WDS system, as I had used the service manual for the G (much easier).

Items you must have:
Power cable (gauge dependent on wattage (RMS))
Power fused (sized appropriately for wattage (RMS))
Speaker wire
Remote wire
RCA cable
Subwoofer
Subwoofer enclosure
Amplifier
1 lot tools/tape/solder/soldering iron

Once I finally figured out the WDS, I found the schematic for the rear factory amp (with DSP, premium sound).



From the above picture, we see that wire numbers 8 (red w/ white stripe) & 18 (brown w/ green stripe) correspond to + & - for left subwoofer, and 6 (red w/ blue stripe) & 16 (brown w/ white stripe) correspond to + & - for right subwoofer respectively. Now the question is, where to find those wires? On the right of the schematic in WDS, we see a callout "X18773". This is the connector number. Further in the WDS, you can find pinouts of connectors. Looking up this one, we find the following.



Along with this, is a stylized picture of the location of the connector.



STEP 1. Remove negative terminal from battery. Never do electronic work on a vehicle with the battery system attached.

Now that we know where to look, and what to look for, we begin by tapping into those wires. These wires are fairly large gauge with stiff, thick jackets, so typical vampire-type in-line splice taps don't work very well. I used a razor blade to strip away some of the jacket and expose the copper wire. From there, I soldered on the + & - of an Monster RCA cable for each the left and right signal. It helps greatly to remove the connector from the back of the factory amp.

A pic of the finished product. I forgot to take pics during the soldering process.



Overall pic of that area



With that finished, we can tap into a switched +12VDC wire to provide Remote Turn-on for the amp. I used the rear power outlet on the right side of the trunk. First remove the deep set cover towards the back, which exposes lots of wiring. Looking closely, you'll see the rear of and the connector for the power outlet. Remove the connector and splice into the green w/ yellow stripe wire. Feel free to verify with a voltmeter as I did.







Now we need to mount the amp someplace safe and secure. Some people mount them to the back of the seats, but I prefer them hidden. Having the 3rd row seat really limits me on hideable space, but I decided to remove the long plastic tray in the covered storage area. I removed the battery cover for working space, but will replace when all is secured.

I fabricated a rack out of MDF for the amp. I doubled the thickness at the top to allow for a true vertical mount. I am mounting via bolt and nut using the factory holes at the attachment points for the long plastic tray. I wanted plain automotive black vinyl to wrap the rack, but all I could find was a felt-backed vinyl. The rack looks fine from the front, but the felt didn't cut well, so the back looks like crap. This hardly matters though.











Now we want to get power to the amp. You should have already removed the negative from the battery, but here's a pic showing where negative connects to the car.



That is also where I landed the negative cable for the amp.

The easiest place to land positive is shown below.





Amp all wired up.



Next, I'm using a temporary sealed enclosure that was gifted to my by a friend. I plan on having an acquaintance build me a custom fiberglass enclosure to blend into the trunk more, possibly using some more of the space under the hideaway cover. Anywho, I calculated the interior volume of the box to be 0.85 cuft, which is smaller than the 1.0 recommended for my sub. While at Walmart getting the crappy vinyl, I bought some PolyFill quilting stuffing. For those that do not know, polyfill essentially makes the sub act as if it's in a larger enclosure. There's no magic number or amount of polyfill to add to enclosure, so use your judgment. I figured I was missing 15% of the airspace needed, so I added the whole package.





The next step is to install the sub in the enclosure, wire it up, and test it out.

Tuning the amp will take a little time. I have mine set pretty well and will soon mount it in its final location, at which time I'll take some more pics and update here.