Some info on setting up your GoPro's for a external mic. This setup gives pretty good audio but, if you aren't on a track or smooth road surface you will still pick up allot of road noise.
Things you will need:
GoPro Hero 3 or 3+
GoPro mini usb to 3.5mm mic adapter (Amazon $12.90)
Olympus ME51SW stereo mic (Amazon $46.95)
Bluerigger 6ft 3.5mm Male to Female 3.5mm stereo audio cable (Amazon $5.49) I bought 2 of these.
Microphone windscreen I bought mine from Guitar Center and got the most dense foam I could find as the outer shield and got 2 more that I cut up to muffle the mic some more
Modifications to your GoPro case: This is really the only thing that requires any modification. I used a drill, dremel, and some small files. You need to cut a hole so the GoPro mic adapter can be attached to the camera.
It should look something like this when you are done:
And with the adapter attached:
I found that I had to block off some of the sound ports on the mic because it was picking up to much ambient sounds. So this is some masking tape and the foam come in. The green tape I just wrapped around the left and right intermediate ports then the whole mic has the microphone windscreen foam wrapped around it to further keep out unwanted sounds.
It should look something like this when done.
And disassembled:
For mounting the best place I have found so far is the little square indention next to the rear license plate light and truck release button.
Routing:
You can route the cables just about anywhere you want you are only limited by how much cable you have. If you mount the camera inside the car you can just run it out the rear hatch lid. You can run it in the top and out the rear of just about any door, hood, or hatch you want. The cable is small enough that is won't distort the closing point of wherever you run it.
The mic will come with a 3 ft cable (THROW IT AWAY) I tried to use it but all I would get is one channel and the other channel was clicking. The bluerigger cable is much better and the mic works as it should.
Also be aware that the mic is powered by the camera. I have not done a test as to how much this burns battery life if any but, something to keep in mind. Adding the hole to your case also will allow you to charge the camera in the case. it will render the case not water resistant though.
I posted a video in the Fast Intentions exhaust is here and the Track/Autocross section if you want to hear it at the track.
Vid Link:
Wnter X at Miller Motor Sports Park 11-16-13
Hope someone finds this useful.