I did an audio test of 4 cheap external mics for the GoPro Hero 4. I'm using the Silver edition. I used a very cheap small stereo mic, a SG-108, a Vivitar, and a Takstar mic. 2 of the mics are junk and 2 are solid. Check out the audio from them all in the video. If you like the video, please subscribe, like and share.
