[Nord Electro 6] Headphones output max ohms ?

[maxpiano]

As volume not only depends on impedance and power, but also on the efficiency factor of your phones, there is no way for a producer to tell in advance which headphones will get enough power to fill in the needs of a player and which don't.

Actually a simple set of electric measurements would tell you all you need about the output. Of course then you also need info on the headphone impedance and efficiency (as you stated). But Clavia engineers have the info on their part for sure, it's just a question of "how technically transparent is Nord as a brand".

So you can't find a lable saying 'fits 250 Ohm' or not.

This is correct. And you are making a good point, because unfortunately few potential customers would likely do the work of calculating voltages, impedances and efficiencies.

You cannot find that info on most other brands instruments as well, you can just guess it in some cases; for example a friend of mine has an issue with his 250 Ohm headphones on the Yamaha P5252 and in fact Yamaha's accessory headphones are all in the lower range (32-60 Ohms) i.e. the "Several studio applications, laptop, PC, Hi-Res MP3 player" range (according to the page posted by pterm, which I put again here https://north-america.beyerdynamic.com/ ... eadphones/)