So you’ve stolen commercial airlines headphones.
Me-he-he, why the fuck you even need them? They are piece of crap! To reduce the urge to steal, manufactures make special airplane headphone jacks, incompatible with normal stereo 3.5mm jack. So how do you connect it to a standard device? In airplane jack each “ear” has its own, independable double wire. Basically, it is two mono headphones paired together, unlike stereo headphones, where one of the wires is shared by both speakers. First and obvious way to connect is just plug in only one of the jacks. Only one ear will be working with both left and right channels mixed to one mono output. Another way is to just cut the proprietary jack and solder a common stereo 3.5mm connector. The third way is to get an adapter. The obvious search for “airplane adapter” gives very misleading results. Such adapters serve for the opposite purpose – they allow you to connect your own standard stereo speakers to airplane media system. Well in case you want to use your own headphones with airplane equipment. But if you search for stereo mono splitter, the result might be a stereo male to two mono female adapter. The female sockets exactly fit the airplane jacks. However, you should be careful when ordering such adapters, as they may have different wiring inside: it may be either a stereo splitter to two stereo outputs, basically allowing you to connect two stereo headphones to one output; it may be a stereo to two mono splitter, basically allowing you to connect two mono headphones to one stereo output; and it may be stereo splitter, where one stereo channel say left goes to one connector, and the other, say right, goes to another. That is the one you need. So it’s safer to purchase cable extenders like this one, they even have the output female sockets marked in different colors, indicating separate channels. So they should fit and work as required: left will be in one headphone, and right in the other. They are also quite easy to solder yourself. If you plan do do that, make sure to use the left and right test signals that could be found on my channel. You should also check speaker phase.