ARC Mobile allows you to optimize select ARC compatible audio devices by using either the internal microphone of iOS devices (for all measurements) and Android devices (for bass measurements) or an optional calibrated microphone (for better results). Optional calibrated microphones, which connect via the headphone jack or lightning connection (iOS) or USB (Android), are included with select products. Please refer to the product’s user manual to see if it ships with a microphone. The ARC Mobile app is available for free to iOS and Android users. Please note that Android phones require a USB OTG adapter to use the external calibrated microphone. Many Android phones come with this adapter.