Now that we're onto absolute horrorposting, get a load these monstrosities originating from a Finnair flight back in 2009.
These were so hilariously awful I just had to take them home and hold onto them. You know, just for the occasional shits 'n' giggles, or perhaps as a healthy reminder of the abysmal depths head/earphone quality can go.
It's almost endearing how these had the usual old school dual prong headphone plug setup, but with a special twist: the second plug could be turned up 90 degrees, converting them from dual TR to single TRS plug. But have two guesses if that system worked reliably? Of course it didn't! So it was off to opening up the plug casing and permanently soldering the wiring to the non-movable plug. Anything for those shits 'n' giggles!
I have no idea of the frequency response of these things, but I'd guess they'd measure similarly to those Korean Airline earphones. Absolutely no highs or lows (and not in the "hurr durr, there's zero base" kind of way, there's literally NONE). And what's left is this horribly boxy and tinny squeeking. Would make an interesting challenge trying to EQ them to sound anything other than absolute shite.
Judging from how it was practically impossible to get them to anywhere listenable volume levels (not that you'd want to...), I would have these to have a massive impedance, but no. Checking with a multimeter, the left channel measured "only" 91 ohms and the right side around 80 ohms (yea, that's some proper driver quality control and matching right here!), not THAT much. I guess the sensitivity of the drivers must be quite legendarily low.
And as a cherry on top and testament to the impeccable shittiness of this earphone model, only one of the two pairs I got from that round trip of two flights was actually properly made and working. Right out of the box (or to be exact, plastic bag), the other pair, A) didn't work at all, and B) had left side shells on both earpieces.
You can't make this shit up.