Disclosure: I’d like to thank 64 Audio for providing me with the Solo for this review. All thoughts and opinions are my own, and 64 Audio had no say or input on the contents of this review.

The 64 Audio Solo marks the brand’s first venture into planar magnetic IEMs, featuring a single 14.2mm planar magnetic driver housed in their familiar aluminum shell design. Unveiled just before CanJam SoCal 2024, this IEM targets the premium market at $1,399, placing it $300 above their well-regarded U4s at $1,100.

What makes the Solo interesting isn’t just the driver technology, but how 64 Audio has approached the typical challenges of planar magnetic IEMs. The single driver design promises coherence, while their dual Helmholtz resonator system aims to tame the often problematic treble frequencies that plague many planar IEMs. The question becomes whether these engineering solutions justify the premium pricing in an increasingly crowded planar IEM market.

I’ve spent considerable time with the Solo across different sources and genres to see if 64 Audio’s take on planar magnetic technology delivers something genuinely different, or if you’re better served by lower-priced alternatives. I will say that the Solo surprised me in a very good way, so let’s get into the review and find out why.

• 64 Audio Solo
• Carrying case
• TrueFidelity Foam Ear Tips (S,M,L)
• SpinFit Silicone Ear Tips (S,M,L)
• Silicone Ear Tips (S,M,L)
• 3.5 mm SE Copper Eight-Braid Cable
• 4.4 mm Balanced Copper Eight-Braid Cable
• Shirt Clip
• Cleaning Tool
• Cleaning Cloth
• Round Sticker

64 Audio clearly put effort into the Solo’s packaging and presentation. The substantial outer sleeve features the IEMs prominently displayed alongside specifications, though the real impression comes when you slide out the inner box with its copper-colored logo – a nice touch that hints at the aesthetic theme inside.

Opening the magnetically sealed box reveals a welcome note from the founder printed inside the lid, which is a personal touch I appreciate from companies. The foam insert catches your attention with repeated 64 Audio logos covering the surface, and the precision-cut spaces house everything neatly. The Solo sits prominently at the top with the cable already attached and wound around a metal insert bearing their “HEAR EVERYTHING” slogan. The presentation definitely feels more premium than other IEM brands.

The standout inclusion here is the copper cables, apparently a first for 64 Audio. One cable has a 3.5mm SE termination, while the other has a 4.4mm balanced connection. These eight-braid cables use 23 x 25 AWG wires with a 0.26Ω impedance rating. They feel noticeably more supple than the previous 64 Audio cables I’ve handled, and the copper aesthetic ties everything together nicely with the color scheme of the IEMs themselves.

The puck-shaped carrying case looks elegant with quality stitching and felt lining inside, though it’s rather large for pocket carry. Not a deal-breaker, but worth noting if portability is a priority.

Lastly, there is a generous assortment of eartips included. You get a set of S/M/L lower profile wide bore silicone eartips, a set of S/M/L SpinFit silicone eartips, and a set of S/M/L TrueFidelity foam eartips. On top of that, 64 Audio provides a nice eartip holder that fits perfectly inside the carrying case.

The Solo feels substantial yet balanced when you first pick it up. There’s a quality to the weight distribution that suggests careful engineering rather than just premium materials thrown together. At 6.9 grams per shell, it’s heavier than some competitors but lighter than you’d expect given the 14.2mm driver inside, as well as the aluminum shell materials.

Shell Build Quality

64 Audio went with T6061 aluminum alloy for the shells, which makes sense for a $1,400 IEM. This isn’t just marketing speak – T6061 combines magnesium and silicon for durability while staying relatively light. The matte black anodized finish feels smooth but not slippery, with just enough texture to provide grip during handling.

What caught my attention was the small lip added to the nozzle, which is a minor but smart design update that prevents ear tips from sliding off when you remove the IEMs from your ear.

The shells follow 64 Audio’s standard universal design, which resembles what some describe as a “tiny kidney bean” shape. This works well for most ears, though those with smaller ear canals might find the fit challenging. The gentle curves create multiple contact points that help with stability, but you’ll need to experiment with the included tip selection to get it right.

Visual Design and Aesthetics

The copper mesh faceplate is easily the Solo’s most distinctive visual element. Unlike the abstract patterns on other 64 Audio models, this copper grille features an array of embossed logos across its surface. It’s not just for show, either, as the mesh serves as the pressure relief vent for the planar driver.

The contrast between the copper mesh and matte black shell creates an elegant look that many consider 64 Audio’s most attractive design to date. This represents their biggest housing update since the Fourté back in 2016, and it shows.

Comfort and Isolation

The apex core technology developed by 64 Audio provides -12dB of isolation, which creates what 64 Audio calls an “unoccluded” feeling. The first time you put them in, you might wonder if you have a proper seal, which is normal. The design intentionally creates an almost open-back sensation despite being closed IEMs. It’s quite unreal how this feels and needs to be tried to be believed. It makes a substantial difference in the overall wearing experience, and almost ruins using other IEMs.

This isolation level works best in quieter environments. If you’re planning to use these on noisy commutes or flights, you’ll probably want something with better passive isolation. At home or in the office, though, the balance between awareness and focus feels just right.

One minor complaint: depending on your ear shape, the cable connector housing can sometimes contact the top of your ear rather than tucking behind it cleanly. It’s not uncomfortable, but you might need to re-adjust occasionally during longer listening sessions. The lightweight construction really helps here. Even after hours of listening, there’s minimal fatigue.

I found the comfort excellent right away, though you’ll want to experiment with the generous ear tip selection to nail the fit. The foam tips in particular seem to work well with the Apex Core system for achieving both comfort and the intended sound signature.

The Solo’s 14.2mm planar magnetic driver delivers a sound signature that feels quite different from typical planar IEMs. Rather than the often analytical and cold presentation many planar drivers exhibit, 64 Audio has tuned the Solo to sound warmer and more organic. The dual Helmholtz resonators clearly do their job here, taming what would otherwise be a potentially harsh treble presentation. If you compare the Solo to other well-regarded planar IEMs, such as the 7Hz Timeless II or Kiwi Ears Aether, you will notice this difference right away.

The 64 Audio Solo is not a demanding IEM to drive, with an impedance of 16 ohms and a sensitivity rating of 100 dB/mW, but I did find that a better quality and generally more powerful source is required to get the best possible sound from it. Using an underpowered source like a budget DAP or cheaper dongle DAC makes the Solo sound lifeless and very thin. Also, keep in mind that if your source has a noisy background or interference, you will hear it with these IEMs.A clean, good-quality source really is required here, which is why I tested the Solo with DAPs like the Sony NW-WM1AM2 and FiiO M21, and DACs like the FiiO K13 R2R and the iFi GO link Max.

How does the Solo actually sound, though? The overall signature leans warm with a slight vocal emphasis, making it quite engaging for vocal-heavy music. It’s not a neutral reference monitor, as this is tuned for enjoyment rather than true clinical analysis.

Bass

The bass response surprised me with how much it behaves like a quality dynamic driver rather than a typical planar. There’s actual decay and lingering presence rather than the quick, sometimes sterile bass many planar IEMs can produce. The quantity is generous without being overwhelming, providing a good impact on tracks that call for it.

Kick drums in Led Zeppelin’s “When the Levee Breaks” have satisfying thump and weight, though the deepest sub-bass extension feels slightly rolled off compared to the best dynamic driver IEMs. Bass guitar lines in Pink Floyd’s “Money” maintain their texture, and you can follow the note progression easily, showing good detail retrieval in the low frequencies.

The dual Helmholtz resonators help shape this bass response, preventing the typical planar magnetic bass from sounding too tight or lacking body. Still, if you’re coming from bass-heavy IEMs, the Solo might feel a bit restrained initially, but the detail and quantity is definitely there.

Midrange

This is where the Solo shines and where you’ll either love or find an issue with its tuning. Female vocals are presented with excellent clarity and emotional presence. Listening to Kate Bush’s “Running up that Hill,” her voice comes through with both power and delicacy intact, showcasing her range with precision and authenticity.

Male vocals tell a different story, though. Deeper voices can sometimes lose weight and sound a bit thin. Mark Lanegan’s gravelly delivery in tracks like “Barracho” doesn’t quite have the chest resonance I’d expect, making his voice feel less commanding than it should.

The midrange has what I’d call a “vocal hump” that brings singers forward in the mix. Beck’s “The Golden Age” showcases this well as his voice sits prominently while the backing instruments maintain their proper positions. Whether you’ll appreciate this depends on how much you prioritize vocal presentation. In my case, this suits my musical preferences very well.

Treble

Here’s where 64 Audio’s engineering really pays off. The treble is smooth and controlled without feeling dull or rolled off. Cymbal crashes in Radiohead’s Reckoner have energy and presence but never become sharp or fatiguing. The dual Helmholtz resonators targeting 5kHz and 8.5kHz clearly work their magic here.

Detail retrieval remains excellent, allowing you to hear the decay of cymbals and the texture of hi-hats clearly. However, some might find the treble lacks the last bit of sparkle and air compared to more aggressive tunings. It’s a trade-off between smoothness and excitement, and I think it works wonderfully well with the rest of the tuning, providing excellent cohesion.

Soundstage and Imaging

Despite the Apex Core technology creating an “open” feel, the soundstage of the 64 Audio Solo isn’t dramatically wide. It’s more intimate than expansive, which works well for vocal-focused music but might disappoint those seeking grand orchestral presentations.

Imaging performance impresses, though. Complex electronic tracks from the likes of deradmau5 remain organized and easy to follow despite the dense layering. Each element maintains its position in the mix without bleeding into others.

There’s a black background here that helps, providing excellent separation between instruments and making it easy to focus on individual elements when desired. Alice in Chains’ live version of “Frogs” demonstrates this well, with the live audience perfectly placed while each instrument occupies its own space.

The 64 Audio Solo leaves me with somewhat mixed feelings after weeks of listening. The engineering is undeniably impressive, as the dual Helmholtz resonators really do solve the harsh treble issues that plague many planar IEMs. Female vocals sound particularly engaging with excellent clarity and emotion, though male vocals can feel a bit thin at times.

The build quality lives up to 64 Audio’s reputation. The T6061 aluminum construction feels solid, and that copper mesh faceplate gives the Solo a distinctive look that stands out from their previous designs, as well as competitors. Comfort is excellent thanks to the lightweight shells and Apex Core technology, creating that “unoccluded” feeling, even during long listening sessions.

But here’s where things get complicated. At $1,399, the Solo faces tough competition from all directions. There are sub-$500 planar IEMs that deliver surprisingly similar performance, and even within 64 Audio’s own lineup, the U4s at $1,099 might actually be the better choice for most people. The Solo arrived late to the planar party, and that timing shows in the value proposition.

If you specifically want a planar magnetic IEM with refined, controlled treble and don’t mind paying premium prices for 64 Audio’s build quality and engineering, the Solo really delivers. Professional users will appreciate the consistent performance across different sources thanks to the Linear Impedance Design, as well as the excellent comfort and extremely high-quality accessories, such as the copper cables and assortment of eartips. But for most listeners, including many audiophiles, the extra $1000 over other planar IEMs might be hard to justify.

Whether all of this is worth your money comes down to how much you value this specific combination of planar driver coherence and tamed treble, because you’ll find excellent alternatives at both higher and lower price points. What I will say, though, is that once you start listening to the Solo, the combination of comfort and sound quality will essentially ruin all other IEMs for you, as the listening experience with the 64 Audio Solo will make you always want to reach for them.

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