Apple only has a single connection on newer iPhones. It's either a lightning port or a USB-C port. Apple will be elimintating ports completely in the future. If you want to use wired headphones with a "mic" connector, you need an adapter. You can't charge the phone while it's plugged in. This is really inconvenient sometimes.
Apple does sell excellent bluetooth headphones, but that's another $200 or more. What to do?
MacBooks still have "mic" ports. You can plug your wired headphones in, but how do I play music from my phone and have the sound come out the headphones?
You'll need to use the "Audio MIDI Setup" app. Plug your iPhone into the USB port and it will show up as a new device.
Enable this device and it becomes available as an input/output device. Now, you need to route music from the device to the headphones. This requires using an "audio program". Quicktime does the trick.
Run Quicktime and start a new audio recording.
Select iPhone from the dropdown. DO NOT select your phone name (Joe's iPhone in this case).
Select "Dock Connector" as the output from the iPhone.
Initially, the sound will be off. Slide the volume control to increase the volume to a comfortable level. Plug your headphones in and you'll hear music.
You will also hear system sounds and sound from anything else running on the computer. This is handy. You'll need to pause music on your phone manually if you get a Skype call.
Problems Enabling iPhone
This procedure is not reliable. The Mac will try to connect to the phone using "System Capture" mode. The order you plug in the phone, unlock it, "Trust" the device, enable it and start Quicktime determines whether the iPhone sees the Mac as "System Capture" or "Dock Connector". The iPhone must connect using "Dock Connector".
Unfortunately, I haven't figured out a reliable sequence to make this work yet. When I do, I'll update the story.
Reliabilty Update (Aug, 2020)
I've found after restarting my Mac, I need to perform these steps to get Quicktime to output audio to my iPhone. Whenever asked to Allow trusting the computer.
- Connect the iPhone to your Mac with the USB cable
- Start MIDI Setup
- When "Your iPhone Name" shows up in MIDI Setup, Enable "Your iPhone Name"
- Start Quicktime, select "iPhone" in the New Audio Recording drop down (NOT "Your iPhone Name" - this is the trick)
- Insert headphones into Mac and your ears :)
- Turn the volume up to at least 50% in Quicktime
- Play something on your iPhone
- You will see the input volume meter in flashing different levels, but no audio on the headphones (most likely)
- Open a Terminal and enter this command:
Enter your login password when prompted.
You should hear music on your headphones now.