Okay, I promised to do a comparison between the Avalon and the Semper, so here it is. Both IEMs have the same configuration: red nozzle and blue filter, with SpiralDot++ tips. These are all my subjective impressions and by no means are they the absolute truth regarding those two IEMs. Bear that in mind, even if I don't keep repeating "to me" or "in my experience".
The most obvious difference is in the tuning: the Semper is sterile and more clinical in its presentation while the Avalon's sound is warmer, natural and more fuzzy, as if each note was wrapped in a warm blanket and given a cup of hot cocoa. Also, the former has bigger headstage and better instrument separation, which coupled with its somewhat higher resolution make the sound sharper and clearer, but also more tinny and there is some nasality to the vocals when compared to the Avalon. Similar to the Elysium, the Avalon is also more analogue in its presentation to IMR's 2020 offering.
While bass quantity is similar, the Avalon has the edge in quality. Bass guitars have more clarity and better resolution, especially the lowest notes, and there's more of a purr to them than on the Semper whose clinical sound encompases the bass as well. Bass extension is on a similar level, with well-defined and clear sub-bass.
Mids are more forward on the Avalon, but due to the overall fuzziness of the sound, they may seem less detailed and slightly veiled, while the Semper's are clearer and snappier despite seeming more recessed due to the bigger headstage. The Avalon's narrower stage also results in worse instrument separation and instruments' apparent sources are located closer to each other.
If vocal presentation is important to you, you will want the Avalon over the Semper. On the former, vocals are more natural, forward and intimate, while in comparison the latter's are more nasal. Obviously, with brain burn-in you stop noticing the nasality eventually. As a result, the Avalon conveys the emotional load of vocals somewhat better. Here, I find, that the Avalon's smaller headstage lends itself to a more cohesive presentation of music. Vocals blend much better with the rest of the musical composition, which was one of my first findings regarding the Avalon, and I support it wholeheartedly. As a result, on the Semper the same song sounds like you're in a concert hall, while on the Avalon you get a more intimate situation, as if the artist were singing just for you.
Where I find the two hard to compare is the highs region. The Avalon is really holding its ground fine vs the Semper, which I didn't expect but which is a welcome surprise. I would even say the Avalon has the Semper beat in detail retrieval, because I've heard new things in songs I thought I knew very well. It feel like the Semper has better extension, however, a smidgen more shimmer in the cymbals. However, here, the Avalon's warmer sound signature may make it seem like its apparent brightness is lower.
Overall, in direct comparison, I feel like the Avalon wins as far as my sound signature preferences are concerned. Its sound is more natural, warmer, and euphonic when compared with the Semper side by side.