Reddit reviews C2G 03174 3.5mm Stereo Female to 3.5mm Mono Male Adapter, Black

It might be because the mic is mono and your signal and cable is stereo but I'm not 100% sure. It should work with a standard stereo cable, at least it does on my Dell laptop (I do this often at work where we can't use the computer's for listening to music, but I can use my personal phone). You do lose a fair amount of quality though and there is often some background noise/hiss.

Anyway if the Mac is specifically looking for a mono adapter that could be the cause. If so this adapter should fix it:

https://smile.amazon.com/C2G-Cables-03174-Stereo-Adapter/dp/B0002EOHX0/

Get a 3.5mm Stereo to Mono adapter. This will accomplish what you're trying to do with any stereo headphone that uses the standard 3.5mm jack.

Example of such adapter: https://www.amazon.com/C2G-Cables-03174-Stereo-Adapter/dp/B0002EOHX0/ref=sr_1_3?ie=UTF8&qid=1482595733&sr=8-3&keywords=stereo+to+mono+3.5mm

So I should use one of these for my headphones or for the mic? :

https://www.amazon.com/C2G-Cables-03174-Stereo-Adapter/dp/B0002EOHX0/ref=mp_s_a_1_4?keywords=mono+to+stereo&qid=1565448575&s=gateway&sr=8-4

(If the info is needed) The mic has a female xlr to male 3.5 mm stereo as far as my knowledge goes. The line in of the H2n is a stereo 3.5 mm

Nothing on that page would do what you really want.

The things that are labeled "stereo to mono" imply that they are intended to mix a stereo signal into a mono signal. Unless they have some internal resistors (like that home made cable -- which they certainly do not have) then they would simply short the left and right outputs together to connect them to the mono side. And as mentioned it's not really good to short outputs together in general. But even it were OK to short the outputs together it still wouldn't work because the mono side of those adapters will only connect to the tip of a plug. So you'd only get the mono mix in one side of your headphones.

Those "stereo to mono" are really meant to take a mono output and send it two both sides of a stereo input. For example, to send a mono source to both sides of a stereo recorder.

OK (just in case anyone gets any bright ideas), you could connect one of these to the headphone output. Then plug one of these into the first adaptor. Then plug the headphones into the second adapter. That would short (kind of mix) both sides of the output to both sides of the headphones. But don't do that! Because it does short the outputs together and they aren't meant to be shorted together that way. I only mentioned it in case someone saw some potential there and wanted to give ti a go.

You need one of these,

Yeah that, or http://www.amazon.com/C2G-Cables-03174-Stereo-Adapter/dp/B0002EOHX0/ref=sr_1_1?s=electronics&ie=UTF8&qid=1459276062&sr=1-1&keywords=1+8+mono+to+stereo+adapter

How are you planning on sending the signal to the house? You're either going to need a 1/8" to 1/4" converter. Or get a Y cable that goes to 1/4" and then another mono->stereo

Just need to add one of these: https://www.amazon.com/dp/B0002EOHX0

It'll take the mono out (from either the left or the right output) and make it come out both headphone drivers.