When I play with Pianotec (Blüthner @ 423Hz), I hear some sharp ringing around 4460 Hz. I was able to eq this out with the equalizer in Pianoteq (by first exaggerating it in order to find it), but still I'm not completely satisfied with the result.
So I think that with some sound analysing, I could find the artificial spikes in the frequency profile, and correct them with the Pianoteq equalizer.

I think, the analysis could be done with ARC3 (demo version) and some microphone (ZOOM H2n? May not be very accurate, but maybe accurate enough for my purposes?).

But, maybe it can be done in an other way? Creating white / pink noise, capturing it with a mic and then analysing the result in some software?
I'm completely new to this. So, if anybody has some suggestions: yes, please!

I still have ARC System 2 (v.2.5.0) since ARC had firstly been released a number of years ago.  It is readily another potential solution —like today the preamps that allow both mid-side and left-right mic input equalization— to problems ofttimes inherit with users wanting to have genuinely real impressions of course of some true acoustic piano before them  —and out of just a couple loudspeakers or inexpensive consumer grade monitors.

Clearly, it has been marketed toward music listeners to compensate by its patent suppression of obvious irregularities players or a single listener can usually encounter in the sounds out of small to mid-size monitors, and, loudspeaker placements in likely their untreated rooms.

Seemingly it makes the total ease and convenience of any loudspeaker listening just as enjoyable as purported headphone music listening inside the rooms.

Well said Amen,

Warmest regards,

Chris

Clearly, it has been marketed toward music listeners to compensate by its patent suppression of obvious irregularities players or a single listener can usually encounter in the sounds out of small to mid-size monitors, and, loudspeaker placements in likely their untreated rooms.

Seemingly it makes the total ease and convenience of any loudspeaker listening just as enjoyable as purported headphone music listening inside the rooms.

Hope this helps someone,

Warmest regards,

Chris