Review: Symphonium Helios: Skunkworks.

The Helios is a $1099 quadruple balanced armature in-ear-monitor developed by Symphonium, a well-established Singaporean manufacturer in collaboration with Subtonic, a small consultant firm launched by three experienced and respected community members: Ken (Leneo), Kevin and Corn (toranku). I was excited to try this project as it represents the successful commercialization of enthusiasts’ passion for sound, like Crinacle’s multiple industry partnerships, Amar and Eudis’ Aurorus Audio and Zerousen’s PhilPhone.

Custom painted PhilPhone – credit to Den-Fi

I was sent this unit in exchange for my impressions. Although there is a glaring conflict of interest given the fact that I am well acquainted with some of the members of Subtonic, this is my forthright opinion.

Design & Ergonomics

The Helios comes well presented, with a healthy selection of silicone ear tips, a supple 2-pin quad-braid copper litz cable, a message from the creators with the serialized metal card and a hefty metal “tin” for storage & transport, which is protective but awkward to pocket. The robust metal shell is somewhat chunky for a quad BA IEM, but fit is comfortable and weight is reasonable. Ken recommended achieving a deep fit past the second bend of the ear canal for best performance, but I was unable to obtain a reliable seal given the angle of insertion, opting instead for a shallower approach which, to me, brought very little in the way of sonic sacrifice.

The unboxing experience.

Whilst fairly inefficient in the realm of IEMs, most portable sources like the Fiio M11 Plus LTD used for this assessment will adequately drive it.


The Helios is an exciting all-BA monitor, flavoured by the textural features of its driver type. Tonality is V-shaped, whereby a hefty sub-bass shelf is followed by a slightly forward upper midrange and an exceptionally well extended treble region.


The shelf, whilst approaching 10 dB, is somewhat conservative in its spread, being mostly erased by around 100 Hz. This allows for a convincing sense of rumble with deeper notes, with practically no intrusion into the fundamentals of most instruments and vocals. It also carries a remarkable sense of body for a BA, reminiscent of the IER-M9 and some EarSonics monitors – in fact Subtonic confided that during development, blind listeners were unable to determine that the woofer was a BA. Whilst my listening was obviously sighted, I still found the bass to have some tell-tale characteristics of that driver type. Compared to a good DD (e.g. CE-5, IE900, Z1R), attack is somewhat softer, and whilst there is a convincing sense of initial decay, it doesn’t linger quite as much in its sustain. Note definition is nevertheless surprisingly good: I was pleased to hear how the Helios lacked the “one-notey” aspect of some of its less articulate counterparts, making this one of the better balanced armature portrayals of bass I’ve heard despite the qualms.


Midrange demonstrates very slight upper register emphasis, with snappy leading edges and mostly unrestricted microdynamic contrast instilling life into strings and snares. Decay is short-lived, producing clear cut notes. This is a fast-sounding IEM, which combined with the FR, makes it texturally dry. It is also one of the grittier balanced armature midranges I’ve experienced, with a sense of bite that is reminiscent of classics such as the UERM. Along with the intimate stereo image it projects, I found its energy enjoyable with modern jazz genres and thought the resolution was exemplary. However, some musical cues such as male vocals and brass may lack some foundational richness, which may turn away those who prioritize timbre.


Top end is, in my opinion, a highlight of the Helios. Lower treble is tuned relatively neutral, demonstrating some of the crudeness expressed in the upper midrange, further adding to the vivid nature of the IEM. Upper treble is pushed forward, with an exceptional sense of extension, generating a potent sense of air and sparkle that is tolerable given a relative mid-treble recession. However, this isn’t necessarily a smooth-sounding top end: some of the tubeless BAs and ESTs (e.g. Andromeda, U12t, Erlkönig) will sound more ethereal and less etched. There definitely is some slight coarseness up top, but despite that knock on its resolution, there is plenty to spare. My most significant qualm would be a lack of body or “weight” in the leading edge of lower treble, mainly in cymbals, which you’d find in a few alternatives like the IER-Z1R. This may be a limitation of the driver topology, as I can hardly recall having heard this from any BA tweeter.


I am quite impressed with the product that Symphonium and Subtonic have crafted. The Helios expresses an unambiguous identity through its energy, incisiveness and strong technical performance. Sure, the bass does some masquerading, but this is undeniably an agile all-BA IEM. It isn’t the safest recommendation for those looking to extract a deeper level of timbral and textural information or a relaxed listening experience, but is likely to please audiophiles seeking a tastefully aggressive and gritty sound.

I look forward to seeing what Subtonic achieves later down the line, especially as they bypass the inherent restrictions of an all-BA design and fulfill their plans of branching towards the horizon of high-end hybrids. The Helios is a strong performer, and whilst not ground-breaking, its root as a passion project by audiophiles crafting their version of an ideal sound and sharing it with the world is admirable…

… and hopefully the beginning of an illustrious adventure.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s