Sound Analysis and Comparison to IT03.
In this analysis/comparison section I used both IEMs with their stock cables. IT03 performance does scale up with a cable upgrade, like the latest CB13 or even CB12s, but for consistency I kept cables stock. Ironically, CB12s is a stock cable of IT04.
The first thing I usually notice when start listening to headphones is the soundstage, and here both have the same staging depth which projects the sound more out-of-your head, while IT04 also adds more expansion to soundstage width. The signature of IT04 is more balanced, with a more revealing, brighter, transparent tonality. In comparison, IT03 is more v-shaped where the mids are thicker, a little warmer, not as forward as in IT04, and you have more emphasis on bass and treble with a little smoother tonality. I do hear IT04 as being more resolving and more transparent when compared to IT03.
The bass extension is similar, though IT03 has a little more sub-bass rumble and mid-bass punch. IT04 bass feels a little tighter, faster, and more controlled. Also, due to a more forward presentation of mids in IT04, its bass is more balanced and has a perception of less impact in comparison to IT03. Lower mids in both are closer to neutral, where IT03 lower mids are a little north of it with more body, while IT04 lower mids are a little south of neutral, with a leaner body. Upper mids in IT04 are more forward, brighter, more transparent, with improved resolution that leads to a better retrieval of details. In comparison, IT03 mids pushed a little back, have a smoother warmer tonality which leads to a little less resolution and less transparency in comparison to IT04. I don’t hear IT04 as more analytical, but rather more revealing, leaner, and balanced with improved resolution and transparency. With high frequencies, both have a well defined crisp airy treble extension where IT03 has a little more sparkle while IT04 has a little more control.
Imaging in both is pretty good, with a relatively accurate placement of instruments and vocals, sound never gets congested, well separated and layered, though IT04 has an upper hand here due to its more transparent tonality and wider soundstage. Another interesting observation, while testing with lo-fi sources, I found IT04 to have a wider soundstage expansion which makes me wonder if it has something to do with its 16ohm impedance that pairs up better with higher output impedance sources vs IT03 (8ohm) which pairs up better with lower output impedance DAPs.
Overall, I find IT04 sound signature and tuning to be more mature (more audiophile tuned), more balanced (improved coherency), more revealing, more transparent and with higher resolution. In contrast, IT03 has a smoother tonality with a fun tuning and more emphasis on bass and treble where mids are pushed slightly back, not as forward as in IT04.
IT04 vs IT03.
In terms of the design, both have a very similar ergonomics with custom universal built, but there is one noticeable improvement. The nozzle of IT04 is a little longer, and as a result you don’t have to push IT04 as deep into your ear as you would with IT03. Those who had issues with IT03 shell comfort due to a corner mold piece of the inner side of the shell pointing toward concha symba area of your outer ear, now there is a little more distance between IT04 shell and your ear. I also noticed a finer mesh grill on IT04 in comparison to IT03. I don’t accumulate too much wax, but I would expect IT04 to do a better job of keeping small particles away from entering the nozzle.
Without a doubt, premium CB12s cable (included stock with IT04) is a big step up as well, in terms of ergonomics (thinner wires), flexibility (more pliable), 2.5mm termination with a separate 3.5mm pigtail adapter, and a design with matching aluminum plug, y-splitter, chin-slider, connectors and adapter connectors. Also, mmcx connectors in the shell don’t stick out as far as in IT03, and connection is tighter, not easy to turn the cable. This is another plus, because when joint is loose, you get dirt and moisture inside, affecting the reliability of the connection.
The faceplate of IT04 has a more premium design with a carbon fiber artwork and InTune label. I do like it, but also wish the little iBasso triangular logo would have been featured somewhere in the corner of the faceplate. Of course, this is just a personal nitpicking comment based on my preference since I like that little logo. Overall, IT04 shell looks more compact and more premium.