By default the iPhone alarm sounds both through the headphones and speakers (understandably), is there a setting somewhere to set the alarm to only go through the headphones?
(The use case is I want to wake up with the alarm but not wake everyone else in the house)
No, unfortunately there is no such setting. Your best bet is probably to use a 3rd party app with alarm clock functionality. That way it will only play the sound through the headphones and not the speakers. The main disadvantage is that you would need to remember to keep the app launched before you go to bed each time.
You could mute the voice before inserting the earphones and then put in the earphones and set the volume. This way the alarm sound will only come through the earphones because you have muted your phone, not the earphones.
I found a solution, albeit it might not be ideal for some.
Instead of using the alarm app, use the reminders app, as the reminder app plays only through your headphones while also letting you set a time for the alarm.
The only 2 downsides that I can see could cause issues are that it plays the set sound bite once, instead of looping it like the alarm app (solution is probably put multiple reminders back to back), as well as that the reminder app splits time into 5 min intervals, preventing you from say, setting an alarm at 6:48 for example.
I recorded a silent alarm and then used that as the sound and set the alarm to vibrate. This way, the vibration wakes me up but not everyone else. The vibration works really well if you put the phone next to or under your pillow. The phone can get warm if it is under the pillow though so I usually put it just to the side.
Use the built in clock app for your alarm and it will bypass the cable and come out the speaker. All third party alarm apps fail at this...
