Hello Wipfli,
welcome to the HP German Customer Forum and Thank you for your post.
If you want to create the post in the English Forum, please click on this link: www.hp.com/supportforum
If you can actually speak/write German, it would be not just good for you but for the others Members very helpful, if you could edit your post to German.
In the right upper corner of your post, you will find Options - just move over the mouse cursor and select Edit Post.
A hint to you question: You only must use the name of the Mac or the IP of the Mac and the shared folder. e.g.: Cyrill's iMac27Jan2014\HPScans
With the IP of the Mac, we had the better experience.
Note: Pleas be sure, that the folder has full permissions and the SMB-sharing is active. The printer use SMB-sharing.
MfG
Maik