Added Steering Wheel Controls & Tweeters to base model 2008 Subaru Impreza WRX
For my main 2008 Subaru Impreza WRX worklog, look here. Here I'll talk about the speaker and steering wheel control mods that are specific to a WRX.
First, here she is:
I love this car.
I planned to install my own stereo equipment (mostly taken from my previous car), so I bought the base model WRX. I added steering wheel audio controls and door tweeters myself for cheap, normally part of a $2000 option package. If you want to do the same, here are the Subaru part numbers you'll need:
94251FG060 & 070: "Cover gusset door RH & LH". (Tweeter trim panels.) $13 each.
83154AG001: "Switch satellite". (Steering wheel buttons) $122
023812000: "Flange nut" (Steering wheel nut) $1
I'll also mention the plastic bezel around the clock. I bought a spare since I modified mine, but that's not part of this writeup.
66208FG010 (Panel Clock U4) $16
There is no standard tweeter mount in the tweeter trim.. I had to hack apart the back of the trim panel, jerry-rig a strap to hold the tweeters in place, and then glue the trim assembly together... But my Infinity Reference tweeters did fit, and in the end it looks totally clean. (Note I glued the trim together, but it still clips and unclips from the door normally.)
The trim is polypropylene (PP) which is one of the hardest to bond plastics there is... The only thing I found that worked is 3M Scotch-Weld DP-8005. You can buy it at www.mcmaster.com. There's also a slower-curing version, which I might recommend. This stuff cured so quickly I could only work with a tiny bit at once. Stays rubbery for a day or two, but eventually gets rock hard.
Even in the base model, there are wires running to the tweeter. However, these are skimpy 24 gage (I think) wires connected in parallel to the door speakers without a crossover, so I ran brand new speaker wires anyway. It's not too hard to run an extra speaker wire through the rubber boot in the door jamb.
Also in the base model, the wiring for the steering wheel audio controls is all there. The switches are a drop-in replacement, and in the stereo wiring harness you'll find a Brown wire and Yellow wire that carry the signal. Of course, you'll need something to interpret the signal -- in my case, I programmed a PIC microcontroller, but you could also use something off the shelf like the PAC SWI-X Steering Wheel Audio Interface. (Cheaper at other websites.)
For reference, here are the resistances you will measure between the Brown and Yellow wires:
Mute - 22 ohm
Vol up - 90 ohm
Vol dn - 200 ohm
Mode - 360 ohm
Seek up - 690 ohm
Seek dn - 1.15 ohm
Nothing pressed - 4.7k ohm
You do have to remove the steering wheel to replace the switches. The service manual does not call for replacement of the steering wheel nut, but for safety I did so anyway. (My old Ford Explorer did require replacement, which is why it occurred to me.) It's only a buck, so I splurged.
If you don't have a service manual (which, by the way, you can access online through Subaru for not too much money) here's the procedure:
1. Make sure the steering wheel is oriented straight so you can get it back on correctly when you're done.
2. Disconnect the car battery and wait at least 20 seconds.
3. Remove the airbag via the T30 Torx bolts on the sides.
4. Disconnect the airbag from the wire connectors at the rear of the airbag itself. There are little yellow clips you pop up with a tiny screwdriver, and then the connectors will come off easily.
5. Mark the steering wheel orientation, and then use a steering wheel puller to remove it. (I didn't have the right kind, and on a brand new car I was able to get it off by just pulling really really hard... but I nearly damaged the airbag wiring, so I don't recommend it.)
6. Pretty self-explanatory from here... Disconnect the cruise control switch, unscrew the cruise control and trim panel from the rear of the wheel, screw in your new cruise control and audio button panels, and put everything back together.
7. Important: Tighten the steering wheel nut to 39Nm or 28.8 ft-lb of torque. Make sure the steering wheel is fully seated. Mine took some wiggling.
8. Probably less important: airbag screws should be tightened to 10Nm or 7.2ft-lb
9. Sweet!! Steering wheel audio controls!
Next was the door speakers. I originally considered leaving the stock rear speakers, but after seeing what the stock speakers looked like, I definitely decided to replace them all! After seeing them, I'm amazed they sounded as good as they did, which still isn't saying much.
Sadly, it's a completely non-standard mount, so you pretty much have to make your own plywood adapter plate unless someday there's an aftermarket option. (I found none when I looked.) I took some crummy pictures with my phone because my camera was broken, but hopefully you get the idea...
I cut pieces from plastic milk jugs to protect the speaker a little from rain. The stock speakers had a little overhang, so I tried to copy it.
Also, you see I found room to mount the crossovers in the front doors. It was a tight squeeze, and I had to position it juuuuust right, but it did fit without much hassle.
I hope this helps and inspires! For more on the rest of the Car PC install, check out the link at the top of this post.