Some up-to-date thoughts/impressions on the IT04 from a post I made on another thread:
So, by way of introduction, I'm doing some A/B testing between two iBasso setups:
1) DX150, AMP7, CB12s, IT03.
2) DX200, AMP8, CB13, IT04.
After quite a bit of listening (with a LOT more to come, haha), I'm not convinced/entirely on the same page concerning some of the descriptions I've heard flying round about the IT04, specifically with regards to its bass (e.g. things along the lines of "same quantity as IT01 and IT03, but more refined") and overall sound signature ("very similar to IT01 and IT03, best of all worlds etc"). Possibly I may have said some of those things myself, who knows?
I of course wish to stress that we all hear things differently and I totally respect the impressions and opinions of the many fine posters on here; this is just my own take, to add to the menu of impressions and to hopefully help those trying to figure out if it might be a good fit for them, sonically speaking
I personally don't feel that the IT04 has any accentuation in the bass region. It's tight and articulate, but I wouldn't compare the sound signature of the IT04 with the IT03 or IT01.
The IT01 was a fun tuning done extremely well; L-shaped, prominent bass and good levels of detail and musicality.
The IT03 has this big soundstage, and lots of detail which add up with everything else to making it seem (to me) only very mildly V-shaped.
It leans more towards the audiophile sound signature and quality for me (compared with IT01).
I really love the IT03 bass;
for my personal tastes, it's the best-executed implementation of a low end that I've yet heard.
It never seems to bleed into the mids or colour the sound signature, but it IS always present, giving weight to the music, never letting it sound anaemic and can hit very hard and deep when called for, and bring out elements of timbre and tone (especially in bass and percussion) that others simply can't.
Conversely, the IEM that the IT04 most reminds me of is the Empire Ears Zeus XR.
The Zeus blew me away when I heard it at CanJam and was/is probably the best IEM I've heard so far to date (with the caveat that for certain genres, I would prefer the kind of bass you get from the IT03).
I felt it had incredible extension, detail and clarity, allied to a huge soundstage.
These are the kinds of qualities I'm feeling with the IT04 as well, and an overall similarity in tuning between the IT04 and the Zeus (compared with any other IEM I can recall hearing).
To be clear, I'm basing this on a one-off demo of the Zeus a year ago (albeit one that's indelibly burned into my brain!) and I'm NOT saying the IT04 is or isn't as good as the Zeus (if someone wants to lend me their Zeus, I'd be happy to further investigate how they compare and what they have in common, haha).
I'm also not saying that the IT04 is as bass-light as the Zeus! It's got that dynamic driver after all, and there's some bass presence there for sure, just in a much more mature, neutral-reference style sound with a tinge of musicality.
I think the things IT04 has in common with previous iBasso IEM's would be the big, holographic soundstage, separation, detail and clarity that I love on the IT03, but taken to a significantly higher level.
This is just my personal opinion, but I would say that's mostly where the similarities occur, and also where they end.
If you're looking for bass warmth and colouring like on the IT01, or strong bass capability and presence like on the IT03, I would caution you to try to demo the IT04 first (or be prepared to embrace something new and different!).
I've seen quite a few posts, that collectively seem to end up giving the impression that it has all the bass of the IT01 and IT03 ("all of your bases are belong to us" lol), but I am not really hearing it that way.
To me, iBasso have gone in a whole new, upwardly-mobile direction with the IT04 and I salute them for it.
I would just add a note of caution for those who might think it's essentially an upgraded IT01 or IT03; to me, it's a quite different tuning altogether.
I think it's an outstanding IEM that offers something approaching TOTL audiophile sound at a fraction of the price.
I think I will favour my IT03 for rock music. The IT04 certainly performs well here too, but I personally find myself missing the unique bass/percussive qualities of the IT03 (I think the IT03 have spoiled me, haha) and miss them in those kinds of songs.
Conversely, for acoustic, pop, EDM, hip-hop, classical, folk, jazz, alt-country, Bollywood and pretty much everything else, the IT04 are taking it to a whole new level and I am enjoying them immensely