Pimax support said that the right jack is reserved for MAS and won't work with anything else. It didn't work with normal headphones but did work with 3-d party Oculus Quest headphones
Crystal feedback from Berlin roadshow. : r/Pimax
F-16 helmet plus Pimax 5K+ = more fun : r/dcsworld
Pimax 8KX is completely underrated! : r/virtualreality
Everything You Need to Know About the Pimax Crystal : r/virtualreality
Pimax Crystal hands-on: a headset with astonishing visual clarity : r/virtualreality