The lack of consistency here makes me wonder well,…wtf?, lol. My iPad is a Pro and the Mac i have them connected to is a newer MacMini both running current iOS and OSx. I have had issues with the inexpensive 4 Port Hub which resolved as soon as I connected to other USB ports either on the MacMini or my keyboard. I suspect signal interference within the passive hub. I have powered USB version coming today from Monoprice which may help to keep signals properly directed. I will say that my USB A to USB B cords aren’t the snuggest fit in the H9’s. More than once I’ve lost connection(s) and found that the USB connector was either loose of not completely inserted. New USB B cables coming today as well!
I guess the end age here is find the way which works best and is most reliable…Maybe H9’s like to hang out in groups of three!