After listening to the Sennheiser IE600 for a week and running it exclusively off the Apple dongle, I took away an impression that this IEM had no imaging whatsoever (
I even made a post on r/headphones about it). The song I was using was
Reflection by Tool where in the intro, every piece of the drum kit is in a different spot. I came to expect this imaging because my LCD-5 paired with Oor and Bifrost 2 rendered the song so. So on a whim this past weekend I hooked up the IE600 to my desktop chain, and bam! The imaging was back. I then tried the Apple dongle to Orr via a 3.5mm to RCA cable (i.e. dongle is only a DAC now) and again the imaging was non-existent and all the drums are in one overlapping blob in front of me. So it wasn't the Orr adding the imaging- it's something the Bifrost 2 is doing.
Imaging to me seems like a binary criteria- either it's there or it isn't. Not something subjective like bass texture or treble airiness. So my conclusion is that the Bifrost 2 is doing something to the digital signal that the DAC in the Apple dongle isn't. I want to believe all DACs are the same... I really wanted to but this to me has been a major revelation.