I have the same problem, same here too:
head-fi org/t/689100/3-5-mm-jacks-4-vs-3-conductors
tomsguide com/forum/id-2166958/bass-output-subwoofer-galaxy-star-pro.html
I have Samsung J2. It works great with any 3-pin/4-pin headphone but doesn't work with PC speakers, almost no bass, something...