So here I was at Hong Kong airport waiting to travel to Shenzhen and in comes an email from 64 Audio about a new release. I was expecting something new from the brand for a while now, with its last audiophile-centric release (the Aspire 4 feels far more pro-user oriented) having been launched over a year ago. With the Duo having been discontinued recently, there was also a gap in the lineup ready to be filled. I was expecting maybe something along the lines of a U6s, or even the mythical U12s (U12t w/DD bass), but not a single planar magnetic set. Solo was a surprise in a lot of ways, and clearly everyone else was equally surprised at CanJam SoCal when the product first made its public debut. Amidst the largest CanJam show ever, I don't think a lot of people were able to try out the Solo which—given the high ambient noise level at the event—was probably a good thing. The Solo is not a traditional open-back set, but it has a more open feel to the sound and certainly isolates less than most sealed IEMs. When you play something at your regular listening volume, you are still likely to lose yourself in the music though—just be aware that others in your close vicinity may also end up listening inadvertently.

The more open presentation, combined with the more tightly controlled tuning, makes for a compelling listening experience that is still not for everyone. 64 Audio has done a commendable job highlighting the strengths of this 14.2 mm planar magnetic driver while curbing the weaknesses better than anyone else I am aware of. You get a decidedly 64 Audio house sound here, down to the upper treble peak that somehow lines up with the usual tia driver air, and even the forward mids + relatively relaxed ear gain that have made many fans of the brand. Bass is aplenty, clean, and hits deep, which complements the Solo having excellent resolution across the board and handling layering like a champ. Imaging is extremely precise too, allowing for the Solo to be a tool for music monitoring and mixing too combined with its accurate soundstage. It's easier to notice faults in recording too, but the overall tuning is still musical. Those wanting a purely neutral experience may want to look elsewhere thus, as well as those who require a more isolating set. A side effect of this open presentation and tonality is some notes can be on the thinner side, and there's also the part where your experience is going to be contingent on you achieving a deep and secure fit. A shallower insertion depth can influence the mid-treble behavior with the two Helmholtz resonators employed to help keep the typical IEM planar magnetic driver treble under a tighter leash. Take your time, tip-roll if you must, and ensure you get the smoother and fatigue-free experience the Solo has to offer.

At $1399, however, there will no doubt be questions asked about the value proposition. This is all the more likely to happen as a result of planar magnetic IEMs having had a very recent resurgence, even compared to the fast pace of IEM R&D in general. There have been plenty of offerings in the last 2–3 years from various Chinese brands, and even more coming up now with increasingly mature takes. There are also contenders from Western brands which cost similar, if not more, but generally go for even more colored tuning that makes for a specialized/niche audience more often than not. Not that the Solo is going to be universally pleasing, it still has shades of metallic timbre and the upper treble peak can be disconcerting if you are sensitive there. My counterpoint is that we don't see such comparisons with other driver types, simply because they have been more commonly used, and ultimately the driver type/count matters less than what you do with it. In this context, the Solo resolves some of the issues beset by other sets and does so in a novel manner. The implementation of older acoustic engineering concepts such as Helmholtz resonators, in combination with an electronic shelf filter, helps address a modern problem here with planar magnetic IEM drivers. This cool engineering implementation merits acknowledgement, even if some may ultimately feel this was a solution done for a problem that could have been outright ignored. There is still plenty of potential with planar magnetic IEMs if I say so myself, and the Solo is a welcome addition in my books. Yet there remain a few more variables here than I'd like to see to allow for a uniform listening experience with this current implementation. I can only suggest people try and demo the Solo in a quieter environment while also taking the time to ensure a proper seal in your ear canals. Anyone who wants to try a new, more resolving take on the established 64 Audio house sound or even looking to see what planar magnetic IEMs are capable of will certainly find the Solo more than just intriguing.