Can I use a Shure BRH440M with an iPhone 6?
Yes. Use a TRRS (Tip - Ring 1 - Ring 2 - Sleeve) 3.5mm male phone plug (used with standard iPhone earphones) to connect the BRH440M microphone and headphones.
The BRH440M wiring designation is as follows:
Mic Send : Red wire
Mic Return : Black wire
Mic Ground : Shield; it surrounds the red wire and black wire
Headphone Audio Left : Green wire
Headphone Audio Right : Orange wire
Headphone Audio Ground/Return : White wire
Solder the BRH440M wires to the TRRS phone plug as follows:
Tip to Green
Ring 1 to Orange
Ring 2 to Black, White, and Shield
Sleeve to Red
You can listen to music with the headphones when not on a phone call. When a call comes in, you'll be able to hear the caller and use the microphone to talk to the caller. You will not have sidetone (return monitoring) i.e., you will not hear your voice in the headphones.