LCD i4 vs Tia Fourte & U18 Tzar.
Comparing the i4 with IEMs is not actually fair, as the i4 seems to fall in a different category according to its design, construction and use case. Someone used the terminology 'In-Ear Headphone' to describe the i4 and, I think the person was spot on because, the presentation of the i4 is much larger than regular IEMs out there. But if there are 2 IEMs that could compete, it would be the Tia brothers from 64Audio.
Fourte and U18 are IEMs that defy the limitations of IEMs to present a very large stage. While their stages are probably the best in class, they can’t quite keep up with the stage of the i4. According to its open back design and the driver size, i4 presents a larger stage. But the real strength of the i4’s design lies in the size of the instrument images it creates in the stage. They are open and large, almost close to the size of images created by full-size HPs. In contrast, Fourte’s and U18’s instrument images are still small, but that is to be expected.
In terms of resolution, Fourte and U18 have much better perceived resolution as they have very good isolation. Isolation is critical when it comes to being able to hear low-key high frequency details. And since isolation is not a feature of i4’s design, i4 can appear less resolving. But the true capability of the i4 driver can be heard when listening to the bass notes. It is highly resolving and very fast as well. The Tia twins also have an enhanced lower and upper treble that help with the resolution ad detail retrieval. But because of the treble enhancement, the Tia twins sound over-articulated and artificially detailed.
Getting into the signature and individual aspects of the tuning can result in a wall of text. So, to keep it short; U18 and the Fourte have very energetic characters with good bass and sparkly treble. They are well suited for electronic music. Between the Fourte and the U18, U18 has better balance in the tuning which makes it more versatile. But still neither can recreate a natural timbre as their mid-range lacks naturalness and the treble is over detailed. And so they are not great for classical. I4 on the other hand sounds lifeless without EQ. But engage the DSP or EQ provided/recommended by Audeze, and the tuning gets close to a headphone target curve, which makes the i4 sound very natural and accurate in its timbre. The balance in the signature makes it very versatile and is capable of handling any genre of music you throw at it.
Oh, one more thing. Fourte’s bass is a highly resolving bass. Its treble adds definition and texture making it a very technical bass and yet, it retains the characteristics of the DD like the liquid decay, good rumbles and extension. It is not an accurate bass presentation but is one geared towards fun and amusement. I4’s bass presentation on the other hand is more accurate. It is a clean bass that does dynamics and extension so well, without having the need to be enhanced. I would rate both the bass equally but for different reasons.
Hope that helps!