I received my AK240 and started listening on Sunday. It's now Wednesday and I just spent the last hour comparing the sound quality to my RAWK100.
I'm surprised. While the 240 sounds good the midrange is more recessed and jazz guitar and piano solos seem less engaging. The bass is bigger and the highs slightly sharper. I think the 240 has a blacker background but the midrange on the RWAK120 sound more organic.
I'm using Shure SE846's with a custom cable and these Shures are new so I'm going to switch to my 535's and also try my Focal Studios.
Overall I'm not blown away like I expected to be. I'd say the differences are somewhat subtle.
What's not subtle is the UI/ergonomics of the 240 - so much nicer to use in every respect.
The battery is terrible though. For the comparison I've only been using 16/44 and battery hasn't budged on the 100 while it's down to 90% on the 240.
So I guess the question I have is : how much more can I expect the 240 to change during break in? I've probably got 30 hours on it so far.
Anyway, SE846 (or shall I say all SExxx) is a vocal-concentrated IEM and AK240 does not make much difference in just that aspect comparing to its predecessors. It will be even more the case if you mainly listen to vocals, especially pop's, though they should still sound more powerful and richer on AK240. Personally I would say an all-round IEM benefits more from upgrading from previous AKs. I would suggest you grabbing a balanced cable for it since balanced out is where AK240 truly shines as much as it shines more for some and less for others.