On Thursday, December 27, 2018 at 7:12:00 PM UTC-8, wrote:
Whats the difference between Magnetic & Crystal headphones?

Magnetic headphones (like most earbuds) are low-impedance and have DC
conductivity. Crystal headphones are high impedance (and are capacitive,
kind of like a capacitor microphone in reverse), so have NO DC conductivity.
The likely reason to use magnetic is that a DC path to ground is required
to correctly bias some amplifier stage.

Absent a DC path to ground, some tube-type equipment outputs hundreds of
volts, could be hazardous.