Hello Shooter,
I am familiar with Yamaha Disklaviers in terms of their design, operation, and feel while playing. I also understand that Sennheiser 598 headphones are open-backed (rather than close backed) cans that sit over-the-ear.
Two thoughts come to mind:
1) In and of themselves, it is nearly impossible to experience a set of headphones generating a sound whose source appears to originate from in front of you. Are you sure the Disklavier dealer actually disengaged the acoustic piano's action from the strings while you were listening through the headphones? (Surely then, a person with open-backed, over-the-ear headphones is able to hear more of the ambient room noise ... than of a noise-cancelling and/or closed-back set of 'phones.)
2) In the event that the piano's action was disengaged from the strings, it is still very true that the human mind is extremely good at imagining you are hearing something in front of you. In other words, the mind is quite able to "fill in the blanks" in terms of convincing us that we are hearing an acoustic piano in front of us, even when listening exclusively to headphones.
I am not here to discredit you in any way; I have experienced listening to Disklaviers through headphones and have marveled at their sounds. At the same time, I was always able to tell (while listening to the electronic version of the Disklavier) through headphones ... when the piano's action was disengaged. It sounded darned good -- that is, until the piano's action was re-engaged and I was able to hear both the electronic sound combined with the real piano's strings and soundboard.
Food for thought,
Cheers, Joe
Last edited by jcfelice88keys (05-04-2015 03:15)