That's kind of my point, loud speakers have 'standards' while headphones/earbuds appear to have none. You can buy them with 16ohm all the way up to 350ohm(I think is the highest I have seen). A standard for this item should almost be mandatory considering how close these devices are to your ear drum.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70