Comment by mdasen

The chin is where Apple puts the logic board and speakers for the iMac. Yes, they could move that behind the display, but I'm guessing that'd make the display thicker (which they wouldn't want) and make the thermals harder. It's certainly something they could engineer, after all the iPad has its logic board behind the display. But it's not like the chin serves no purpose and it probably helps with the thermals and sustained performance and probably makes it easier to engineer everything for what is probably one of their lower volume sellers (compared to iPhones, iPads, MacBooks).