Over a month now with both the U-554 and the U-556. Both are shining examples of a well executed IEM. I prefer the U-554 that casts a slightly wider and brighter image than the U-556, that itself leans taller in stage height and more intimate in imaging and stage width. The U-554 has an equisite tonal balance with excellent detail retrieval. It is at once analytical
and musical. You can pause to be critical and dissect elements of a track or simply enjoy the greater whole. With my music library (ambient, instrumental, vocal) I have only on occasion reached for the U-556. As I mentioned previously the U-556 certainly sounds more 'natural' and might have the edge with percussion and bass instruments...but having said that, the U-554 offers me enough bass with good extension to replay all instruments with reasonably good accuracy and has slightly more control down low than the U-556.
To support the excellent tonality both sets have great imaging and soundstage with prominent layering that retains coherency during busy passages. *chefs kiss*
Some observations to help inform any potential buyers:
- U-554 for acoustic / jazz / instrumental music is a no-brainer. However, the uppermids tow a fine line offering excellent presence, detail and texture but as a consequence can become shouty on the odd poorly recorded track.
- For this reason it is even more important to ensure the U-554 has an appropriately deep fit to ward off any uppermid/treble resonance from the ear canal that can add to this effect.
- U-556 has less overall resolution and differs in technicalities with a noticeably warmer and less energetic presentation that makes less refined recordings more palatable. This would be my place to start if you're unfamiliar with this tuning or uncertain how deep your fit will be.
- If you're coming from any other tuning than DF there will be an adjustment period. The BA presentation and the neutral tuning is a refreshing experience. For myself it has almost been a detox from overly extravagant boosts in other sets in regions that simply don't need it. Note weight will be lighter if you're coming from a DD but give it some time.
- Have a selection of appropriate tips to hand to improve the chances of a deep fit. You will know you've gone deep enough when your own vocal resonance becomes much quieter. If you're new to this type of fit, take your time and make it a gradual process over days with short listening periods, your canal should slowly become more accomodating.
My favourite source pairing is with the RU6, high gain, NOS. Paired with the R2R config in the RU6 they put on an incredibly organic and textured show and despite my earlier judgement the RU6 drives these perfectly well. The synergy here is undeniable. The Shanling M8 after much listening time smoothens too much of the natural texture that these little BAs are able to put out and warms things from a tonal perspective.
I've been more content this past month than I have at any point since entering this hobby. Despite this, a part of me is dreaming what Yu9 might be capable of doing in the future...maybe a multi-BA with a similar execution and design philosophy? Would adding more drivers really add anything substanstial? I'm really not sure. For now I'll just enjoy these.