I finally made the call and replaced the Beo4 with a Beosound Essence MKII together with a BeoLink Converter NL/ML.
Problem: How can I join / play the Airplay source (from Beosound Essence) in the Masterlink rooms?
Example: Airplay plays in the living room, I would like to join the kitchen to it (IR Eye with Play button). Radio works as expected, I can press Radio in any Masterlink room and it plays the B&O Internet Radio.
Config: NL/ML Converter as Audio Master
Login to view image
Login to view image
Which one is the Airplay source? Nothing seems to work, everytime I hit A.MEM, the Airplay from Essence stops playing. Login to view image
My workaround: Connected now the Airport express to Line-In of NL/ML Converter, and then Beosound Essence can join that with a long press on the Essence remote - not 100% intuitive :(
Old setup:
Login to view image
https://forum.beoworld.org/forums/topic/guidance-on-masterlink-system-with-10-link-rooms/