This instructable is for anyone who owns a pair of headphones with a detachable cable and wants to add a n earbud. this mod is very situational, I made it because some times I don't want to completely tune out the outside and couldn't justify carrying two pair of headphones if you don't have a detachable cable it's pretty easy to make one, and I've seen an instructable on the subject, alternatively I had an idea which can be read on the last step as to an alternative design for headphones with a static cable, now let's get started
Step 1: Take Apart Your Headphones
pretty straight forward, just take the foam off (carefully) and unscrew the driver from the cup
Step 2: Acquire Your Components
the two extra things you need is your earbud presumably from an otherwise broken pair of headphones. the last piece is the female 1/8" Jack. it doesn't matter whether it's mono or stereo because this Jack is only powering the single ear bud. My Jack was salvaged but I think they can be bought for less than 5 dollars. now before you continue you want to fish the wire from your earbud into the headphone cup in the same way the manufacturer did on the opposite side. if that sounds at all confusing it should be really clear once you get your headphones apart.
Step 3: Solder Your Bud to the Jack
Now remember, you want you wire fed through already or else youre " gonna have a bad time" As previously stated my Jack was salvaged so every ones pinout is going to be different but if you don't know your pinout already, like me, it took me about 10 minutes to figure out. just a tip as to soldering that dastardly headphone wire, you want to use a lighter to burn the wire and when you think you burned all the insulation away, burn it just a second more. you know you did it right when you can tin the wires.
Step 4: Drill a Hole for the Jack
just drill a hole of the correct diameter into your ear cup and glue your Jack into place once it's all put back together your done! congrats!
Step 5: Alternative Method
sorry for the lack of pictures because I didn't actually do this version but maybe if someone finds this useful they can post it themselves. So my idea was use a pair of3 Way switches ( you need 2 for both the positive in the negative because both polls need to be switched ) and attach the wire from the audio source to the middle terminal of the switch you then have to attach the headphones on one end and the earbuds on the other. This would require more cutting into the ear cup and may decrease the sound quality. You would put the switch within the ear-cup that receives the audio and spice everything together on to that . I don't know if that's correctly conveyed so if you have any questions please comment. Thanks for viewing!