Making the sound through headphones easier to the ear

You might try a slight high frequency roll-off using an EQ. Add a subtle downward curve on the right third or so of the EQ controller, just to the point where you hear a little difference. From there you can see if it helps and adjust as needed. If it works you can save it as a preset.

You can try the binaural mode in PTQ and increase the amount of reverb in the mix (under the effects/fx panel).

If you are using presets with microphones, you can always move the preset's microphones farther away from the piano but along the same axis, this will add more room tone and decrease the overall volume of the sound.  You can also increase the amount of reverb in the mix on these settings too, which makes the sound more resonant.

The best microphone experience I've ever had, was to position the microphones exactly where my speakers are positioned. I turned off the compensation and the delay, both microphones at 0 db, without reverb, without effects, just the clean sound of the piano.

Since then, I believe that positioning the microphones where the boxes are placed, or doing the opposite (checking the measurement positions of the mics in the sound recording interface window to later position the speakers / monitors) obviously provides maximum realism and spacing believable. That's because the sound is generated exactly from where it was captured.

I downloaded and tried your piano, I found it very interesting. Do you like monophonic sound?

Thank you all for your suggestions. A combination of EQ and moving the mics a little further away along the axis seems to be a good path. I also tried to make the "Classical recording 2" a little dryer which also seems to have potential. Thank you dklein for your FXP-file, it really gives a authentic experience of an older upright (a little ear piercing in the treble though). And thank you professor Leandro Duarte for your suggestions regarding microphone positions. I think I have to learn more about that and how to get optimal synergy with headphones. Dazric- very good suggestion to copy microphone settings from other  presets, it’s a universe to explore...I hope Modartt will implement more presets optimized for practicing with headphones in the future, that would be appreciated by many I think. Yamaha did that with their latest pianos and it has been very well received.

Thank you very much, I really like it! Unfortunately I don’t have the Bechstein pack but I run it in demo mode. Would you like to share what you did to make it so spacious? I think I have to purchase the Bechstein now...:)