Symphonium Helios

General Information

Driver Crossover - Custom Tuned True 4-Way Crossover with FLAT Technology
Frequency Response - 12Hz - 24kHz, ± 2 dB
Sensitivity - 104dB/Vrms @ 1 kHz
Impedance - 8.5 Ohms @ 1 kHz
Socket - Spring Loaded 0.78mm 2-Pin

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Best Kilobuck IEM?
Pros: 1. Magnificent treble response
2. Superb bass for an all BA set (best I have heard!)
3. Solid technical performance and detail retrieval for the price (better than what you pay for!)
4. Outstanding staging and imaging at its price range
Cons: 1. Shells are on the larger side but fits well enough
Founded in 2015, Symphonium is a relatively new IEM brand from Singapore. Currently they are offering only 5 models on their website, Helios being the flagship costing $1099. Since its release, Helios has been receiving lots of praise and accolades everywhere which is well deserved in my opinion. Alongside its strengths, it does have a few drawbacks that I will discuss as well. Let's dive in.

Disclaimer: I am posting this review as a co-reviewer at Amplify Audio Reviews, a passion project by my friend Mr. @Sajid Amit . You can check out his videos at Check out the video review of Helios - . Also follow our Head Fi thread for latest discussions - There are no external incentives and all thoughts and opinions are of my own. Thank you!

Specs, Build quality and Accessories, Comfort:​

Helios is a pure four driver multi BA IEM, designed in collaboration with Subtonic (the guys behind $5300 Subtonic Storm which took the ToTL IEM scene by storm a few months back, no pun intended). It has a four-way crossover and uses high quality components from Panasonic and Vishay.

Helios comes packaged in a fairly plain looking black cardboard box but I am impressed with the bundled accessory package. Symphonium provides two cases, a hockey puck styled metal case with brand logo CNC’d on top and a small leather pouch. The pouch is only big enough for storing tips and cable though. Although weighty and extremely well built, I wish the metal case had a wee bit more space inside. The 4.4mm 26 AWG copper cable is well made and feels high quality when wielded. Fairly lightweight and doesn’t tangle at all. Alongside regular silicone tips, Azla Sednaearfit tips are provided as well which I find quite generous.


Comfort is fine. Helios sports two heavy and large metal earpieces (T6 Aluminium shells) and the nozzle is on the larger side. I have large ears and rarely encounter comfort issues with IEMs (even IER Z1Rs are very comfortable to me) so Helios gave me zero headaches in terms of fit and comfort but I think they might pose potential comfort issues for people with small ears. I would suggest doing your own research before buying in case you are someone who generally has fit issues with large earpieces. Demo them from a friend first if possible.


Build Quality - 5/5
Comfort - 4/5 (for medium large/large ears)
Accessories - 5/5

Sound (Basics):​

Symphonium Helios is something that I would describe as sub bass boosted neutral. The people behind Symphonium are good friends with fellow Singaporean boutiques Subtonic and Nightjar acoustics and they share R&D. Helios actually has a lot in common with 5x expensive Subtonic storm. In supercar terms, if Storm is the Porsche 911 GT3RS then Helios is Carrera T if that makes any sense.

I want to draw attention to the bass response first because I think bass, especially sub bass, is actually one of the strongest points of Helios which is often overlooked/ not given enough attention in most reviews. Helios exhibits almost non-existent BA behaviour when it comes to bass response and most people will have a hard time distinguishing the bass from single DD sets unless they get very clinical or have generally discerning ears.

Rating: 9/10

Midrange is clean and detailed as opposed to being lush and meaty. People coming from thick and overly smooth midrange might perceive the midrange as slightly thin initially. The razor sharp notes give a sense of incisiveness and transparency to both male and female vocals. I find the Helios to be favouring female vocals over male vocals though. Male vocals are not bad or anything per se, they are still very good but I think the relatively leaner lower mids takes some grunt off them. I have observed no significant upper midrange shout but female vocals can get a bit gritty/shimmery in rare instances. Overall though, I am quite satisfied with the midrange of Helios.

Rating: 8.5/10

Treble is where Helios absolutely nails it and trades blows with IEMs costing several times more. It is smooth and linear with brilliant extension all the way up to the air frequencies. Every instrument in the treble region sounds sparkly and razor sharp without ever becoming hot or splashy. There is some peak around the low mid treble frequencies but that rarely becomes bothersome. If you are someone who likes classical music and listens to a lot of string/air instruments or a rock/metal fan particularly nitpicky about cymbals and high hats then you are going to absolutely love the Helios.

Rating: 10/10


Sound (Technicals):​

Symphonium Helios is a technical powerhouse. If you are into raw details then Helios will not disappoint. However, almost all kilobucks in this range have very good detail retrieval anyway so I will not gush over it too much. Imaging is extremely precise and warrants at least a 9/10 rating. Timbre is great although there are IEMs in a similar price range that have better timbre such as IE900 and M9 for example but Helios is not too far off.

Separation and transparency is where Helios stands out the most in my opinion as far as technical performance is concerned but that comes at the expense of losing some note weight; can’t have ‘em all I guess. Soundstage is above average in its price range. In fact, I think only the UM MEST MK2 and IER Z1R have larger soundstage than Helios in the sub $2000 range and both of them cost significantly more. If you are planning to watch movies or play competitive shooters, Helios is going to be absolutely overkill, especially for gaming.

Rating: 9/10 (Detail Retrieval), 8.5 (Dynamics and speed), 8/10 (Timbre), 9/10 (imaging), 9/10 (Soundstage), 9/10 (Separation and transparency)

Source Pairing:​

Helios is harder to drive than usual. Listening experience will vary greatly depending on the source you are going to pair it with. It sounded the best with Sony WM1ZM2 among all the sources I have tried. But 1ZM2 is a $3600 DAP and I do not think many will run a $1100 IEM from a $3600 ToTL DAP. I would suggest doing trial and error runs with different sources and find out which one works best for you.



Helios is a prime example of how to make a good neutral IEM with solid tuning and technical prowess. If you are someone with a ~$1000 budget looking for utmost clarity and detail with above average soundstage and imaging, then Helios is easily one of the most compelling options out there, if not the best.
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Perfect treble at a major cost
Pros: Treble presentation
Above average staging
Top notch detail retrieval
Beautiful Bass Texture
Cons: Fit fit fit fit fit fit fit
Mids can be super dry and uninviting
Lower mids, mid bass and bass can be a bit too lean
Can be very hard to drive (Pro or a con)
I’m not sure why, but I have been putting off this review for a really long time. I have had the Helios now for about 4 months. I would say without much hesitation that this is a feat of audio engineering. With that said, this is 100% not a 5 star IEM. It has faults that make it an IEM I avoid for a few reasons.

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First thing first, I want to go on a fun side journey. For an IEM, Helios is pretty tough to drive. It sounds fine off most of the dongles I used but I had way more fun running it off of my tube amp or high gain on my RS6. I would call this scalability. The staging, the texture and the overall tone of the IEM changed with the sources I was able to use. The magic of using it on my RS6 or my tube amp really makes this feel like a desktop experience. Helios gets bonus points, because it’s not something I look for in IEMs, but was super fun to try.

I tested it with my Q5k, Hiby RS6, Questyle M15, Apple Dongle and Inspire IHA1 tube amp. The RS6 presents a very warm and tubey tonality, similar to my tube amp, while the M15 is more v shaped and punchy. I was able to pick up varying tonality with source switching. If this is appealing to you, Subtonic Storm and Symphonium Helios have to be the 2 IEMs on your list. It is something very unique and fun. Most importantly, Symphonium FLAT tech assures that other sources will not heavily alter the frequency response. I measured this and found it to be pretty much on point. 64audio also has LID, which is similar, but I had to alter the preamp to make sure I didn’t blow my ears out. Helios is legitimately hard to drive.

Fit and Ergonomics- This is well documented, but the fit sucks. I bought the IE900 for the fit knowing full well the tuning wasn’t for me; Helios was the opposite. I was so intrigued by the presentation and technical prowess that I had to get my hands on it. The shell is big, the nozzles are super long and the treble presentation gets better with a deeper fit. Getting a deep fit here is not particularly enjoyable. I can listen for about 1-3 hours before having to take a break. It also happens to be heavy with the cable sticking up in an interesting position. I think this creates the biggest flaw. The shell weight is towards the outer half of the IEM, while the nozzle holding it in place is fitting deep. This means that the weight is like a see saw only being supported by the canal. This is just a terrible fitting IEM. To note, Symphonium worked really hard on this and the Meteor is a fantastic fit IEM. 3/10


Bass- I found the bass on this IEM a little disappointing. If you have read my other reviews, you would know that my favorite bass is more in the warmth regions which is 200-400hz. Sub bass is nice as it can add to kick drums, but the sub bass meta of IEMs just doesn’t do much for me.
With this said, BA bass be damned. This IEM is both textured and slammy. On songs like How You Like That, the sub bass rattles the head a little and can actually be boosted for more slam. The texture in the sub region is also excellent. Usually, I struggle with sub bass, but this is just too good. The dip starts too early though and leaves the bass to mid bass regions very limp if not dead. It almost makes the IEM feel disjointed. There’s sub bass and then mids, but it feels like something is missing in the middle. This can be fixed very easily with EQ, however, most people don’t wanna deal with that. Due to the quality of the bass present, I will go 7/10. A bit of EQ can bring it a long way, but ultimately isn’t enough bass for a bass head and doesn’t reach far enough for someone who likes lower frequency strings like cellos and bass guitars.

Mids- I don’t really know how else to describe it, but the mids feel very... dry? They seem lifeless and without any sort of lusciousness. This is a clinic on imaging and presentation, but seems to have lost something in the middle. Jerry’s vocals on Cumberland Blues feel sad in a way; Dave Matthews vocals also have the same presentation. For what I listen to, the mids on the Helios are not really a strength. Comparing that to something like my A12t, which feels vibrant and textured, I don’t think the Helios really can compare in that regard. 4/10

Treble- Now this is where things get interesting. Since I have been in this hobby, treble has been a failing point of IEMs. Treble is a double edged sword. It requires finesse to help reveal the air and details in high percussion, flutes and violins. Most IEMs just get too hot *cough IE900 and IE600*, while others forget that treble exists. It seems like most IEMs have given up on treble, but Symphonium nailed something here. The treble extends well along a knife’s edge to the very last octave. High percussion and rides on Marcus Miller’s “Trip Trap” are presented like a perfect accompaniment to his fat bass riffs. Carter Beaford’s opening riffs on #41 are crisp. 99% of the time I find it unlistenable (whoever mixed that album was a treble masochist), but this treble is effortless. It reminds me of my Genelec 8030cs. A perfect balance of detail without pain and air without soaring too high. This is a 10/10 treble IEM and it leads to the next section of what makes it a special piece I have held onto.

Imaging- The IEM world has stepped up its game in imaging over the past few years. My go to IEM for detail and imaging was the JVC FDX1 for so many years. While also having major fit issues, it was also a bit spicy. It was well balanced and brought out details that are often never heard. After a while, I upgraded to the UERR and finally the A12t. These all have stellar imaging, but I would personally put Helios at the top. On orchestral pieces, you can hear pages turning, breathing, things dropping or even the audience coughing. In jazz recordings, you can hear the mannerisms of the player. Keith Jarrett’s moaning on live records or Miles Davis leading on Live - Evil. This is on par with A12t, Gaea, U12t and many of the other high detailed IEMs that are TOTL right now. The big difference is price. Helios’ used price is roughly $800 and new only $1200 placing it right in line with the big boys or even cheaper. If you want detail, like ALL OF THE DETAIL, the Helios is the IEM you want. 10/10

Staging- I would call it above average in stage width and height, but not the most mind blowing thing I have ever heard. It has a very clear right and left image with a well balanced center that projects outwards only slightly more than Meteor. If I had to compare, the Meteor is like a campfire with your best friends, while Helios is more like a larger concert hall and the Mest Mkii is like an Arena. Through most of my listening the widest and largest stage goes to the Mest Mkii or the A12t and I think that still holds true. 8/10

TLDR- This IEM is detailed, it’s neutral, it’s a bit on the dry and clinical side with a touch of sub bass and most of all it’s doing something no one else is really doing. It’s walking that fine line of air and sibilance with knife point accuracy. If, staging, imaging and detail are the only thing that matter to you, Helios is bar none the IEM to buy sub $1500.

For some comparisons

If you like staging more than anything, A12t and Mest Mkii are probably better values
If you like bass, texture and a more natural timbre, Meteor, IE900 (EQed) and A12t are better
If you like a super neutral detail monster with perfect treble, Helios is the answer
If you have tons of sources and like to try them Helios is the answer
If I could only pick one it would be Symphonium Meteor
So not only it wants to fit as deep as Etymotic, it’s girthy as well. Sounds like a nightmare. Do you have to sacrifice a lot of resolution going with Meteor instead of Helios?
@o0genesis0o Honestly, I think it's Helios has a ton more resolution. The Meteor is an amazing IEM, especially for lounging, but in terms of detail retrieval it doesn't come as close to the TOTL end as I'd like. I find the sacrifice for fit and tuning make it a better and more enjoyable experience, but if for sheer resolution, Helios is miles better.
Thanks! Very helpful. I can safely cross the Meteor off my wishlist now.


New Head-Fier
Detailed, Bright, Magical
Pros: Fantastic tuning and tonality
Great detail retrieval, imaging and separation
Scales very well with sources and volume
Coherency across the spectrum
Premium accessories (stock cable and case)
Cons: Fit due to the nozzle size and length
Might be a bit lean sounding for some listeners at first listen

A little background on myself and my audio preferences. I listen to IEMs throughout my workday so I generally get to put a lot of hours into listening to IEMs. I have been very fortunate to have had the opportunity to listen to a number of IEMs. Generally speaking, I enjoy a well balanced sound overall and I appreciate bass quality over quantity with slight forward-mids and a touch of brightness (less warm). Like the seasons, I cycle through a number of genres though my current library is a bit more mid/vocal-centric including but not limited to electronic, pop, rock, acoustic, etc. The following are my impressions which I hope can convey my feelings and thoughts when listening to a set of IEMs. I leave the reviewing to professionals who are much better at doing reviews :)

I was able to get about 80-100 hours on Helios with the mixed listening on the HiBy RS6 and the Qudelix 5k using the stock medium red/black silicone tips.

Helios, named after the Greek god of the sun and sight, immerses you in the music with a breath of fresh air that caresses your skin on a beautiful sunny day while you’re enjoying a leisurely stroll through the rolling green hills.



The bass is very well executed with an elevated sub bass shelf that does not bleed into the mids. While the bass isn’t the most impactful/punchy, it is far from lacking and can slam when called upon. The bass instead focuses on immersing you with detail and texture which is quite addicting with satisfactory impact. I love how the bass is layered with rich texture and details. I prefer bass quality over bass quantity and this minimizes any fatigue with my long listening sessions. I am very impressed that all of this bass is handled by a single balanced armature.

The mids are also quite polished with both female and male vocals coming in clean and crisp. There is a touch of brightness that works incredibly well for female vocals for both Western and Eastern genres. Helios is perhaps one of my favourite sets for listening to Lauren Mayberry from CHVRCHES with the other set being the Shuoer EJ07M. The touch of brightness doesn’t detract from male vocals too much and allows complex male vocals like Andrea Bocelli to shine through. On the other hand, I can see the mids being a touch lean, in particular, male vocals for some listeners though I find that to be a personal preference for most.

I was a little worried about the treble region at first since Helios’ treble is best enjoyed with deep insertion. Unfortunately, I couldn’t get a deep insertion but I was able to find a solid seal with a shallower fit using the stock tips. The treble region complements the bass and mids in a harmonic fashion. The treble region is presented with a sense of realism that comes across organic and feels like you’re in the room with the musicians. It sounds natural without any sense of being artificially boosted and that’s a winner in that region for me.


Engagement, Tonality, Source Pairing, Fit

The overall tonality is quite delightful and the balanced sound allows Helios to scale incredibly with various sources as well as cranking up the volume (for short durations). The symphonic tonality on Helios hits my preferences very well and can be enjoyed for long listening periods without fatigue. In some aspects, it reminds me of the MiM Dark Magician (OG) taken to the next level. The resolution in terms of detail retrieval, imaging, and separation are excellent and are among some of the best that I’ve heard to date.

In terms of source pairing with what I have on hand, Helios sounds great on both the Qudelix 5K (more neutral) and the HiBy RS6, which gives Helios a touch of warmth/colouration and is my favourite pairing between the two. Helios requires a bit more power and volume compared to other IEMs that I have tried in the past on both the Qudelix 5K and the RS6 though it can be easily driven on both.

Helios’ fit is the weakest point for me since I have smaller ear canals as the long and wide-ish nozzles prevent me from getting a deep insertion. It reminds me of my struggles with getting a good fit with the Sony IER-Z1R. This isn’t a problem for me though I can see some users preferring a warmer signature than Helios and I think Triton, the latest Symphonium IEM may be a better match for them.


Closing Thoughts

I went into listening to Helios without much background information or expectations since I tend to find it more fun and enjoyable that way. Had someone told me this was a tribrid, I would probably have believed them. Had someone told me only had 4 balanced armatures, I would have been quite skeptical having listened to the Dunu SA6, SoftEars RSV, and ThieAudio V16 among others; this isn’t a knock against any of those, it just shows how much thought and care went into the for tuning Helios. Helios sits among the top 3 of my neutral with a healthy sub bass boost IEMs and it would probably be my recommendation at the 1K+/- mark for those looking for this type of sound signature, the other being the Monarch MKII for it’s smooth and rich mids. If the fit was better for me, Helios would be an instant buy though it might have a chance of being added to my arsenal in the future. That being said, I enjoyed Helios thoroughly and I am looking forward to what Subtonic brings with their upcoming flagship IEM, Storm. I’m also excited to see what Subtonic and Symphonium will bring to us in the future. Helios is a prime example which illustrates what incredible tuning can do and embodies the phrase, quality over quantity.

Lastly, I want to give a shoutout to Leneo from Subtonic, and Felix from Symphonium for including me in the tour for Helios.


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