you are right, the 3.6Ω one is not for headphone.Thanks for the info.
I recognize the diafragm Takstar uses. I don't know about the others.
The AMT seems not usable as a headphone driver; it looks like a driver for home audio sold by Dayton.
in other hand, not many headphone company can design and produce planar Headphone driver, there are so much premiums.