When I got back to really using IEMs on a regular basis, and added some beyond the original Etymotic ER4-S (which I kept for more than twenty years, even after adding newer designs), I was surprised not just at just how stark a difference various types of tips made - but how much their effects varied with different IEMs.
With the SE846 I liked the Comply tips the best, but using those on an EE Zeus or AAW900 absolutely killed the upper-mids and treble regions. Spin-fits on the SE846 were a peaky mess, but just about perfect with the Zeus. With the Andromeda I couldn’t find a tip at all that would give me a good seal while being comfortable at all … but trying to do so led to this (which has been very useful since):
