Nwavguys old blog describes it pretty well: https://nwavguy.blogspot.com/2011/02/headphone-amp-impedance.html?m=1#:~:text=Headphone%20impedance%20can%20vary%20by,output%20impedance%20of%202.6%20ohms.
Nwavguys old blog describes it pretty well: https://nwavguy.blogspot.com/2011/02/headphone-amp-impedance.html?m=1#:~:text=Headphone%20impedance%20can%20vary%20by,output%20impedance%20of%202.6%20ohms.