Connecting to iMac 27 (Late 2012) OS 10.14.6 the audio connects but the Mic is dead. They work fine connected to my Macbook Pro (2015) and my iPhone. Really like the product. However, my normal operation is to connect to iMac and iPhone at the same time. Listen and calls on the iMac a lot.. then answer the phone on occasion. This works fine with QC 35 on all devices
I'm delighted you like your Bose Hearphones. Please call our dedicated support line for Bose Hearphones Support - 1 800-761-2673. They may be able to help with the incompatibility with the 2012 iMac 27.