Symphonium Audio Helios Review - The Brightest Kilobuck Star


Imagine the following scenario. A flagship IEM is released to lots of hype. Said flagship IEM turns out to actually be pretty mediocre, and the hype subsequently dies. Rinse and repeat, plus stack on a couple hundred bucks more for the next big thing. Well, welcome to the flagship IEM world! Having experienced numerous cycles of this myself, it's becoming increasingly rare that I get excited about an IEM; however, there is one IEM I've been eager to hear for some time now: the Symphonium Audio Helios. Symphonium is a small Singaporean brand, and the Helios is their 4BA flagship IEM. You heard me right. Amidst the omnipresent drivers war and the staggering, ever-increasing cost of flagship IEMs, Symphonium has opted to take a more graceful approach with the Helios that clocks in at a reasonable $1100.

The Helios was also developed with consultation from Subtonic. Subtonic is an upcoming Singaporean audio brand; a partnership between several audio enthusiasts including Toranku of Head-Fi fame and Leneo of Audio Discourse. In the interest of transparency, I regularly converse with these individuals and, as jaded veterans of the Singaporean audiophile scene who have heard hundreds of IEMs, they are some of the most critical listeners I know. That in mind, I don't think it was ever a question of whether the Helios would be good, but rather how good?

Spoiler alert: I bought my own Helios within roughly 24 hours of hearing the tour unit.

Symphonium Audio Helios In-Ear Headphones

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Source & Drivability 

All critical listening was done using my iBasso DX300 and iPhone X with lossless files. The stock cable and stock tips (Azla SednaEarfit and Syphonium silicone tips) were used. Personally, I found the Helios to take a good amount of power to drive, sitting at around 45% volume on my iPhone X to reach my comfortable listening volumes (~70dB). 

The Tangibles

The Symphonium Audio Helios arrives in a discreet, black cardboard packaging. Upon removing the outer sleeve and cover, you'll be presented with the Helios' aluminum case nested in the center and a small assortment of accessories in a panel that slides out from the bottom. Here's what's included in total: 

  • 3x Azla SednaEarfit tips 
  • 3x Symphonium Audio silicone tips
  • Aluminum hockey-puck style case
  • Metal placard with SN
  • 0.78mm 2-pin cable

Symphonium Audio Helios Review |

I do wish some more care was put into the hockey-puck case. I like the general build of it and the large O-ring is a unique touch for waterproofing, but the threading could use some work. It's a tad screechy and it has a tendency to cross-thread when I'm initially screwing it on. Just something that I watch out for as someone who's played with a lot of high-quality knives, flashlights, and gear of that nature. The included cable is a standard 2-pin 0.78mm one, but it does not have pre-formed ear hooks for reasons I'll explain shortly. It is supple and non-microphonic. 

Symphonium Audio Helios Carrying Case |

Moving onto the IEM itself, the Helios is big, and I believe that the sheer size will present the biggest limitation for prospective buyers. It sticks out of my ears slightly, and most ear guides with other cables wrap themselves over the middle of my ear instead of neatly nestling into the crevice between where the ear meets the head. I imagine this is why there is no pre-formed ear guide on the stock cable. When I asked about the size of the IEM, I was told that Symphonium Audio had to use larger tubing to achieve the desired treble extension and that large, high-quality capacitors were used too. Luckily, I don't have any major issues with comfort once I get a seal. Do note that this IEM forms a very tight seal; it definitely has above average isolation once you achieve a deep fit with it. 

Symphonium Audio Helios In-ear monitor headphones Review |

Sound Analysis 

The measurement below was taken off of an IEC-711 coupler. There is a resonance peak at 8kHz; as such, measurements after that point should not be considered entirely accurate. You can visit the site below for comparison to other IEMs that I have measured. 

Symphonium Helios Review |

The overall tonality of the Helios can be considered neutral with sub-bass boost. From the bass up until the lower-midrange, the Helios tracks the Harman 2019 IEM target very closely.

But while BAs are generally maligned for their limp bass dynamics, a notion that becomes increasingly apparent as one begins exploring the upper-echelons of the IEM world is that not all BAs are created equal. Indeed, the Helios is a standout in the BA bass department. This is partly due to its tuning which is concentrated almost solely in the sub-bass regions, therefore emphasizing a high degree of cleanliness and never infringing upon the lower-midrange. But the Helios is no less a slouch in the intangible department either. It actually slams, so much so that I wouldn't mind putting it up there with my beloved 64 Audio U12t. While I don't find it quite as "organic" - the Helios' bass texture leans more dry than the U12t, perhaps due to a lack of mid-bass - the Helios sets the standard at a kilobuck for BA bass. 

The midrange of the Helios continues to follow the Harman target closely throughout the lower-midrange. That in mind, despite the more gentle approach taken to the pinna compensation and the upper-midrange, the Helios' note weight definitely skews slightly thin to my ears. Is this necessarily bad? Not at all, but this is where tonal preference will divide some listeners on the Helios' tuning. Personally, I think it would benefit with some more warmth. I also want to say that the Helios is almost too resolving for its own good here. While I don't hear any exaggerated instances of sibilance on my usual test tracks like Girls Generation's "Flyers" at 0:46, transients seem to have a slight edge to them that makes even very small instances of sibilance, such as on Loona's "Voice" from 0:25 to 0:30, pop more than I'm accustomed to. This is especially apparent when listening with the Azla Sedna tips.

Likewise, the Helios' treble is something of a double-edged sword. I cannot deny that it is wonderfully extended and mostly smooth without any egregious dips or valleys in sine sweeps. But here's the not-so-favorable side of that sword: the treble of the Helios teeters on abrasive to my ears. I have to imagine that this abrasiveness is partly baked into excess air, as swapping off the Azla Sednas for the Symphonium ear tips largely mitigates this issue and brings it within "this might be the best treble response I've heard of a kilobuck IEM" parameters. Incidentally, when I dropped the tour unit off with Super*Review, he had very similar impressions between the two ear tips. But either way, the timbre of the Helios's treble still seems somewhat distinct from the bass response which is surprising given that this is an all-BA IEM. This sentiment applies to the midrange to a lesser extent; at times, I could even mistake the Helios for sounding more like a hybrid than it does a BA IEM!

Symphonium Helios Review |

You might see where I'm going: the Helios doesn't sound as coherent as I'd like. As with IEMs like the Thieaudio Monarch and the Moondrop Variations, this feeling is ostensibly baked into the tuning to some degree. From the Helios' razor-sharp bass shelf, its slight dip at 200Hz, and to its excellent treble extension, it all culminates in a more segmented if not clean presentation. Furthemore, I get the impression that Symphonium and Subtonic have indexed too heavily for individual aspects of the Helios' sound and that their IEM has missed the forest for the trees so to speak. Along these lines, the midrange brings out unwanted micro-detail, the treble has too much air resulting in slight harshness, and the subsequent timbral inconsistency is partially because the bass is so good for a BA. For what it's worth, these are definitely some of the better problems to have. Your average listener probably wouldn't pick up on the coherency issues, and the excess treble air would likely be a boon for most listeners. 

Technical Performance 

It doesn't hurt that the Helios has a strong technical foundation with almost zero weaknesses in the departments I usually index for. Let's begin with detail. Detail is not stunning, but it is pretty darn good. As one might imagine, the Helios' excellent treble extension aids perception of reverb trails and sonic minutia that would otherwise be lost on lesser transducers. Take for example that faint ring to the backdrop of Taeyeon's "I Found You" which usually only presents itself to me on my two-channel speakers. Transients are also sharp without noticeable blunting thanks to the clean, segmented tuning. 

As for more latent intangibles, the Helios doesn't let up. Imaging is slightly out-of-head and the Helios sports sharper positional incisiveness than the Andromeda 2020 in A/B. This is especially apparent when it comes to left-right channel distinction. Vocals and instruments panned directly to the sides of Sawano Hiroyuki's "N0VA," for example, have a quality with which they float and wrap around the head oh-so-satisfyingly. Yup, the Helios actually has some backwards imaging! It follows that the Helios' layering chops are excellent, maintaining nuance between various instruments even on dense, epic-orchestral tracks like Thomas Bergersen's "Dear Mr. Alien".  

Now, I normally don't mention dynamics - gradations in loudness - because 90% of IEMs aren't worth talking about for this metric, or only worth criticizing for their lack of it. But while the Helios does skew toward some unwanted loudness, it's also surprisingly dynamic for an IEM. For both macro and micro-contrast, the Helios takes top marks at the kilobuck level from this reviewer. Even in A/B with the Elysian Annihilator, one of the few IEMs I'd consider to have good dynamics, I was surprised to hear that while the Annihilator sported better macro-contrast and quicker transients, the Helios traded blows in the micro-contrast department. In general, transients on the Helios are quick with ample zest, and I find myself glued to the hard-hitting, intensive ride that is BoA's Deluxe album.

I know. It sounds out of character for such an unrelenting critic like myself, but I'm genuinely hard-pressed to ask for more in terms of technicalities. In fact, technicalities were my biggest point of contention before hearing the Helios, as I already had a rough idea of how the Helios would sound based on the FR graph. Suffice it to say that the Helios didn't disappoint. You (or at least certainly I) wouldn't know this IEM toted a mere 4BAs if it weren't for the product literature!

Symphonium Audio Helios in-ear headphones Review |

Assessment of Value

Here's a shortlist of some IEMs that come to mind when we're talking about "the best kilobuck IEMs": 

  • Campfire Audio Andromeda 2020 ($1100)
  • Hidition Viento-B ($1000)
  • Moondrop S8 ($700)
  • Sony IER-M9 ($1000)
  • Thieaudio Monarch ($730)
  • Unique Melody MEST/MEST MK2 ($1000/$1500)

Clearly, the Helios is playing in very competitive territory. There are many established IEMs circling the Helios that would be more than happy to take a bite out of it should it falter. Comparisons below were done via direct A/B where possible. 

Campfire Audio Andromeda 2020: The Andromeda 2020 has a warmer, darker sound that makes its mark with its holographic imaging. In tandem with its lackluster BA bass and dynamics, the Andromeda 2020 is an IEM suitable for listeners who want an IEM to kick back with, to relax, and to soak in its unique presentation. The Helios has a leaner sound and demands attention, sporting aggressive dynamics, sharper resolution, and BA bass that actually slams. While I can definitely still see a case being made for the Andromeda 2020, I sold my Andromeda 2020 in favor of the Helios. 

Hidition Viento-B: The Viento-B has some strong similarities to the tuning of the Helios, but in most respects, you can consider the Helios a Viento-B on steroids with more bass. The Helios has better BA bass, a more balanced midrange, and a more linear, extended treble response. Personally, while the Helios' treble toes the line, I found the Viento-B's treble to be outright abrasive. From memory, I find the Helios to be a solid step-up in the technical department too. It has better imaging (sharper positioning and soundstage size) and a more natural timbre with less intangible grit. 

Moondrop S8: The S8 tracks to the Harman Target more closely in the upper-midrange, and then eschews the target for good amounts of air like the Helios. Head-to-head, I do find the Helios to have even more sparkle and air than the S8, as the S8 has something of a minor recession in the mid-treble. Detail between the two, however, is comparable and they trade blows for their layering chops in A/B. I'd say the S8 even has a slight edge in terms of coherency. Where the Helios clearly pulls ahead, though, is in its impactful dynamics and standout BA bass. The Helios also sounds more open owing to less mid-bass and perhaps the larger nature of its shells. For me, the Helios is a step ahead in the technical department, as it should be for $400 more. 

Sony IER-M9: The IEM that many readers will recall that I've dubbed the kilobuck benchmark in the past, so it was only fitting that I A/B these two IEMs to confirm my thoughts on the Helios. As I alluded to earlier, I prefer the bass tuning of the Helios. That said, I was more pressed to decide between the two for bass intangibles; the IER-M9's bass still maintains a more DD-like tactility to my ears. But where the IER-M9 really draws the short end of the stick is in its dynamics and treble response. It is a very flat sounding transducer and it's treble response, while delightfully sparkly, lacks appropriate initial impact to percussive hits. The Helios runs circles around the IER-M9 in the dynamics department and has a smoother, more airy treble response. Generally, the Helios also sounds considerably more open and has sharper resolution because of how warm IER-M9 is. I'm not sure if the Helios is actually more precise with instrument positioning, but these factors sure lend to that perception. 

All that being said, when you throw the IER-M9's whole package into the mix - accessories, build, fit and a $100 price differential - I think you could still make a good argument for the IER-M9 remaining top dog. But on the basis of sound quality, I would attest that the Helios is better and noticeably so in A/B. 

Thieaudio Monarch: It's not really a contest between these two IEMs, at least for me. They have a very similar tuning profile; the Helios just has more treble extension and presence in those final octaves. Where these IEMs part ways considerably is in the technical department. The Monarch has great macro-detail, no doubt, but its overall sense of detail, imaging, and dynamics are mostly just average for $700. It's certainly behind the Helios for me on those fronts. That's also ignoring the Monarch's coherency which is another step behind, despite the Helios not even being a stronger performer for that metric as I expanded upon in my sound analysis above. 

Unique Melody MEST/MK2: The OG MEST and MEST MK2 are both very solid IEMs that have been met with lots of acclaim this past year. That said, I think they have some tough competition against the Helios. The OG MEST, with its uncanny sense of separation, might have a small edge over the Helios for imaging. But the OG MEST also has some compression issues to its midrange (which sounds quite digital) and its treble which has a tinny characteristic. The MEST MK2 fixes these issues to some extent, but trades some of the OG MEST's resolution and imaging chops. The Helios doesn't make compromises. It sports comparable resolution to the OG MEST and outclasses both IEMs in the dynamics department. That's not to mention the Helios' treble which is simply a step ahead of the ESTs being used in the MEST IEMs. 

The Verdict

There's no question in my mind that Symphonium has released a highly competitive IEM for its respective price bracket, one that is worthy of kilobuck benchmark status. Is it top-tier material, though? To be blunt, no. Not quite. It lacks that last leg of refinement which would place it amongst greats like the 64A U12t, the Empire Ears Odin, and the Elysian Annihilator. It's also not far and away better than everything else in the kilobuck space, or it wouldn't cost what it does. But is it...better? Yes, I think it is. There is a strong possibility it is the best sounding kilobuck IEM on the market today. In that vein, I have zero qualms giving the Helios my stamp of approval on the basis of sound quality. I think it's safe to say that Symphonium and Subtonic have a bright - a very bright - future ahead if the Helios is any indication of what they are capable of. 

Reference Tracks

  • Aimer - Hakuchuumu
  • David Nail - Let It Rain
  • Everglow - DUN DUN
  • Girls’ Generation - Galaxy Supernova
  • Illenium - Broken Ones
  • Joe Nichols - Sunny and 75
  • Keith Urban - Defying Gravity (2009)
  • Keiichi Okabe - Weight of the World (NieR:Automata Original Soundtrack)
  • Sabai - Million Days
  • Sawano Hiroyuki - Best of Vocal Works Remastered (2020)
  • Taeyeon - My Voice (2017)Tiffany - I Just Wanna Dance

Symphonium Audio Helios In-Ear Headphones

Regular price $1,099
Sale price $1,099 Regular price $1,099.00
In Stock
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