The built-in iPhone microphone has gotten very good, but it can’t compare to a dedicated mic setup. Right now, you can grab the DJI Mic Mini wireless lav setup for just $109. You can also step up to the DJI Mic 2 if you want to max out your options. Then, attach the mic transmitters to your subjects with magnets, clips, or lanyards. If you want the best possible audio quality, upgrade to DJI’s Mic 2 setup.