What is the proper name for the type of cable that can combine two mic input into one?

Question

Simply put, I have two lav mics with 3.5mm plugs and they're both mono. I want to combine them into one mic output without changing them to stereo, meaning I want the mics to stay mono.

However, for the life of me, I cannot figure out what the adapter cable is supposed to be called. I can't find any on the internet to do what I want. I always end up with this kind of cable which splits the headset part with the mic part.

Which isn't what I want, I want them BOTH to be for mics, not only one.

So I would like to know what the proper name is for the cable I have in mind so that maybe I can narrow down my search and find one.

Answer 1

You want a 'headphone splitter' because what you're trying to do is divide the contacts equally between two identical devices by simply running them in parallel. You're running two TRS jacks to one TRS socket.

Whether that's actually going to be successful you'll quickly find out. Generally, you don't combine inputs by stuffing two plugs in one socket.
It might work, it might be noisy, it might drive the impedances too low to function correctly. If you're hoping the device you're connecting to has enough power to drive two mics… you might be lucky. You might be luckier if the mics are battery-powered rather than relying on external power.

Basically, this is a 'try it & see if it works' scenario that probably has never been tested by a pro.

Your second picture is for a headset [headphones & mic in one unit] - headsets use TRRS, headphones use TRS.