Symphonium Audio Helios English Review


Interferences at 1000




Construction and Design




  • Excellent treble.
  • Technical and analytical sound.
  • Remarkable tuning.
  • Bass is quite good for a BA driver.
  • Good tuning.
  • It is a nice touch that they have included the impedance of the cable.
  • Robust construction.




  • Big problems when pairing them with most of my sources: noise, interference, clicks, etc.
  • Very heavy metal case, which limits its use as a carry case.
  • Fairly sized leather case.
  • Limited accessories, despite the inclusion of Azla SednaEarfit tips.
  • Simple design.
  • The cable connection to the capsule is not well integrated.


Purchase Link


Link to the Store




According to its website: «Symphonium was conceptualised in early 2015» in Singapore. Its founding members did not agree with the current offer and decided to create their own IEMS. They currently have 3 models: the cheapest is called Mirage ($169), in the mid-range is the Aurora ($248) and the most expensive by far is the model I am currently reviewing, called Helios, priced at $1099. This is a pure four-driver multi BA, designed in collaboration with Subtonic. Built to last, it is constructed from the T6 variant of AL6061 aluminium alloy. It has a 4-way crossover, uses high-quality components from Panasonic and Vishay and is accessorised with Azla SednaEarfit tips. We’ll see below if all this helps the Helios to sound as its price and features would suggest.





I want to thank Symphonium Audio for giving me the possibility to test their product. But, specially, I want to thank SenyorC from Acho Reviews channel, who very kindly proposed Vertex ( and me to participate in this little tour.
Below I link his reviews and videos, in recognition of his work.


Acho Reviews





  • Driver Type: 4 BA drivers.
  • Frequency Response: 12Hz – 24kHz, ± 2 dB
  • Sensitivity: 104dB/Vrms @ 1 kHz
  • Impedance: 8.5 Ω @ 1 kHz
  • Cable Impedance: 0.20 Ω (2.5mm), 0.25 Ω (3.5mm), 0.28 Ω (4.4mm) @ 1kHz
  • Cable: 26 AWG Pure OCC Copper
  • Connector Jack: 2.5mm, 3.5mm, 4.4mm
  • Capsule Connection Type: 2Pin 0.78



Sources and Handling


Normally, I have never included a section on the use of sources and their pairing with the IEMS to be reviewed. But, on this occasion, I feel I must share my experience of using the Helios with many of my sources. Mostly because it has not been pleasant. One of my favourite balanced sources is the Tempotec Sonata E44. Connected, as I usually do, to my PC, all I could hear was noise, interference, even crashing the Foobar2000, which I use as a player. I switched to the Hidizs S9 Pro with a similar result, then to the Earmen Sparrow with no improvement in performance. Then I opted to use the Hidizs DH80s connected to the Tempotec V1-A. Nothing improved.
Then I decided to listen to my colleagues who had reviewed this product before. With an impedance of 8.5Ω, it is clear that you have to use sources with very low output impedance and all the ones I have used have been. But I have not found this to be the problem. I might think that the USB ports on my PC are very noisy, but I use several types of USB ports, including additional PCI-Express cards. In the end and recommended by my colleague Vertex, I used the Qudelix-5K and both via Bluetooth and PC, the sound was very good. Using other sources with transistors, such as the Burson Audio Playmate also proved to be adequate. But, in the end, I will stick with the combination of the S.M.S.L Sanskrit 10th MKII + iFi ZEN CAN. Other sources I used were the Earmen TR-Amp, the DAP xDuoo X3II, both with acceptable results, and the E1DA #9038D, with ambiguous performance. Sometimes as good as the Qudelix, sometimes as bad as the other conflicting sources. And it is worth remembering that the #9038D is very powerful and has an ultra-low output impedance.
Continuing my search for other compatible sources, I have also used my smartphone connected to many of the above dongles. I have to admit that the performance was superior to the previous tests (my PC and the Tempotec V1-A), but I could not get a pure or interference-free sound at all times.


My thinking is that this flies in the face of what is written on their website and I quote literally:


Infinite Linearity
Featuring Filtered Linear Attenuation Tuning (FLAT) Technology, a propriety circuit developed in-house with Subtonic, Helios will not be affected by impedence mismatch due to difference in source used. You will be able to listen to the same unimpeded sound regardless of the device you are using.


I don’t know how it will have worked out with other users, but with me, the above paragraph does not match what I have encountered in my tests.


On the other hand, with the impedance and that sensitivity, you may need to use a source that provides a good voltage as well as a large current supply, it is not easy to drive these Helios, if you like moderately loud sound.


Finally, with the intention of avoiding mistakes, I have also tested the Helios with one of the best cables I have, the ISN C16, without finding any difference, nor any improvement.





The package received consists of two items, a black cardboard box and a black leather-like zippered case. The case has a soft, grey interior with flaps on the sides, like a pouch. In it is the cable with 2.5mm connector. The case is relatively small and the cable and IEMS assembly fits somewhat snugly. The other element, the black box, measures 173x111x47mm. It has the brand name written in the centre, in medium-sized letters, and the model name on the base, in smaller letters. The ink used is white. On the left side there is again the name of the brand and the model. On the right side there are three explanatory icons. On the back side, on the base and in small letters, it says «Made in Singapore, Lah». All of this is written on a cardboard cover that slides up or down, leaving a completely black box uncovered. After removing the lid, a rectangular metal plate with the brand name and model can be seen on the bottom half. On the upper half is a cylindrical, flat, heavy, all-metal box with a screw-on lid, on the surface of which is written the brand name in light relief. Both elements are protected by a foam mould, covered with a velvety surface. As I said, the box is quite heavy, with an inner foam base, as is the top of the lid. After unscrewing it, you have access to the two capsules, a cleaning tool with fork and brush, as well as a copper cable with a 4.4mm plug.
Finally, in a somewhat hidden section of the case, there are the silicone tips. In the narrow base of the box there is a loop, if you pull it open a small drawer containing a metal plate with the serial number engraved on it and the silicone tips. There is a set of three pairs of Azla SednaEarfit and another 3 of Symphonium itself. In summary, the complete contents are:


  • Both capsules with Azla SednaEarfit tips.
  • One 26 AWG Pure OCC Copper cable with 2Pin 0.78 connectors and 2.5mm plug.
  • One 26 AWG Pure OCC Copper cable with 2Pin 0.78 connectors and 4.4mm pin.
  • 3 pairs of Azla SednaEarfit tips, sizes SxMxL.
  • 3 pairs of Symphonium tips, size SxMxL.
  • 1 cleaning tool.
  • 1 metal serial number card.
  • 1 metal screw box.
  • 1 zipped case.


As I said, the zippered case looks like an additional accessory, because it is not in the box. It is just the right size to hold the cable and capsules securely. The metal box is a bit bigger, but as a carrying case it is heavy and bulky.
6 pairs of tips seem too few to me, even though one set is from Azla.
The cables are OK, but I would have preferred one 3.5mm and one balanced. Although I think one is another additional accessory.
All in all, a sober packaging that is appreciated, but with minimal accessories for so much money. It has to be said that, for my taste, the metal plates are superfluous, I don’t see any use for them. They could have replaced them with more tips or other things.



Construction and Design


The capsules are made of a variant of the stronger AL6061 aluminium alloy, called T6. They are complete black and their shape has a tendency to an equilateral triangle, but with some rounded sides and corners. The surface has a slightly sandblasted texture. The outer face is flat and on the side of the base is written ‘Symphonium’ on the right capsule and ‘Helios’ on the left. The letters are capital letters in white ink. At the top corner is the 2Pin 0.78mm connection, mounted on a transparent plate and embedded in the body of the capsule. The rim mixes flat faces with rounded corners. The inner face has a flat side that slopes down towards the nozzle. The mouthpiece is relatively long, with a length of 6.5mm and a diameter of 5.75mm. The length of the nozzles is still somewhat longer because they are mounted on an inclined cylindrical base. They are protected by a pair of thick, metallic grids. Despite being made of metal, the capsules are not very heavy.
The cable has 4 stranded strands of 26 AWG Pure OCC Copper, covered with a transparent plastic shield. The sleeves of the 2Pin connectors are black cylinders with a red or blue ring, depending on the side. The connections are straight and uncovered. There are no ear guides. The integration of this cable with the capsule is not very adequate, as it is very long, with the base of the 2Pin exposed, giving a rather poor integration sensation, aesthetically speaking. The pin is a black metal doughnut. The splitter piece is a cylinder bevelled at the ends and depressed in the middle, but with a rounded shape. Very similar in shape is the jack connector sleeve, but the bevel is only on the end of the cable and the part near the connector is horizontal. The cable is not very thick, has a good feel and little tendency to coil. It is a detail that they specify the impedance of the cable.
Internally, they mount 4 BA drivers (although I have not been able to find it on their website, all the reviews say this). I think they have been designed by Symphonium themselves. They use the FLAT (Filtered Linear Attenuation Tuning) system, a proprietary circuit developed by Subtonic. They integrate a 4-way frequency crossover made with high quality components from Panasonic and Vishay.
The construction is good, the design is somewhat simple. Aesthetically they don’t look like they cost what they are worth. The nozzles are a bit long. The set is good but I wouldn’t single it out from other constructions, nor from other designs. I find them sober, flat, simple, but functional.



Adjustment and Ergonomics


Such a long nozzle with an inclination that is not the most ideal, results in an insertion that can neither be deep nor medium, at least in my case. With a shallow insertion, together with these long nozzles, the capsules are somewhat separated from my ears. On the one hand, no part of the inner side touches my ears, only the tips. In that sense it seems good and comfortable, especially because the tips I use fit my anatomy very well and the capsules don’t move. But the floating feeling of the tips is not what I like the most. I would have preferred more integration with my ears.
On the other hand, the passive isolation I get with my foam-filled tips is very high.







In my opinion, the Helios have a lower-case u-profile, with emphasis on the sub-bass, high mids and first half of the treble, with a good punch of air. The descent from the sub-bass is fast, cleanly transitional and the high mids are sustained in a fairly linear fashion well into the treble. Although the treble feels well extended, it is not an eminently bright profile because there is a great deal of control in that response. There is an emancipated clarity, with a clear, relatively bright timbre, but tuned to be pleasant yet sparkling. I can’t make the profile feel sharp, because it has a good balance, albeit with eminently cool features.





The easy test to tell whether the bass is coming from a BA or a DD is to play pure tones from 20 to 50 Hz. The result is eloquently unambiguous. And, in this case, it is no different. But the better these notes are reproduced, the better the quality of the BA driver. Here you can see that the resulting typical reproduction is clearly perceptible up to 40 Hz. This sound is more like a vibration than a low-frequency oscillation and is audible than sensory. But from this frequency onwards the sound becomes more natural, it loses that high degree of colouring and becomes a more natural sound, but without sounding like a good DD. In my opinion, there is that classic BA timbre in the bass, but I can’t deny that, when playing real music and not those pure tones, the result is more normal and natural. Apart from this test, which is really critical and perhaps even unusual, the low end response is very good. But I expected no less from a $1000+ IEMS. Actually, I would have preferred a hybrid configuration with a DD driver for the bass, but this is a personal matter and now it’s time for the classic low end review.
Again, the low end has a moderate colouration that fades away as the frequencies increase. The punch in that lower part is emphasised, which makes this effect more audible, although it shouldn’t be. Even so, the response is smooth, with a rough texture, the result of vibration. In this sense, this characteristic is more beneficial than harmful, as it gives it a descriptive touch that I like. It is very positive that the Helios hold up very well in sub-bass saturated, poorly etched and dirty LFO playback, which denotes great quality. Not only do they hold up well, but they also have a remarkable level of energy, something bass-lovers will appreciate, if they are kind to their timbre.
In terms of technical capabilities, the bass is very fast and the decay is also fast, which makes each hit very concise, very defined and without aftertaste. It is clear that there is no bleed from the lows to the mids, which is the reason for this speed and the tuning focused on the lower end. These characteristics, on the other hand, slightly limit the width and depth of the scene, as they are not very expansive in this area. The recreation of planes is not very remarkable either, despite the precision of the notes and their level of accuracy.





I find that the mid-range possesses an analytical capacity that makes them very neutral, clean, precise, concise and dry. They can even sound too sparse at times, which makes them lose their three-dimensionality.
The first half of the mid-range is lighter and provides a thinner, less dense sound, which gives less body to the male voices and instruments better represented there. This is something that still enhances the sense of precision and finesse of the notes, increasing the clinical, high-resolution feel. These thin, sharp notes are spaced well apart, but together they do not add up to establish a corporeal substratum that expands the sound and gives it cohesion. It is a concrete and precise representation, which can even be enhanced with cooler sources, or moderated slightly with warmer sources, but without ever appeasing this character.
The second half has an emphasis that rises evenly, but carefully, to reach a level where clarity becomes canon, the treble shining with splendour, fullness and extension. It is clear that the union of this profile with the analytical character, causes a very pronounced sensation of cleanliness, with a high level of transparency, which squeezes the notes even more. There is not a hint of darkness, nor is there warmth, the execution is explicit and effective, without embellishment, beyond the accuracy and straightness of the notes. I must comment that I like the analytical sound, but I would have liked to have had a fuller and wider sound, not so rinsed and polished.





The treble is the area I like best, it has the necessary point of excitement and is cut off at the critical moment, where sibilance is kept at bay. Yes, there is no doubt that brightness is felt and that all notes have flashes, but the speed is such that such bursts are very fleeting, offering a sense of almost absolute control. Add to this the linearity of its extension, and the high end never feels omitted, but is an important protagonist within a sound that seems destined for its own showcasing. The extra-resolute character of the Helios finds its best asset in this range and that enhances the final result. There is no aftertaste and the characteristic dryness is now a virtue, generating a quick, fleeting and ephemeral beauty that disappears before it gets annoying. The sensation of air feels a little more limited, but it is capable of lending a volatile character to the elements in this range, though not enough for the rest.



Soundstage, Separation


As already mentioned, the sensation of such a well-defined sound and its expansive limitations offer a relatively wide scene, with good depth and better headroom. But the amount of vapour and the ethereal feel is perceived as restricted. Despite the high level of resolution and note definition, the lack of substrate does not generate enough physical sensation to personalise instruments or voices within the soundstage. Thus, their placement is accurate, but their representation lacks weight, body and three-dimensionality. There is a remarkable level of separation and a great sense of transparency, the sound is very clean and diaphanous, but its development is observed in only one direction, forward, as if it were slightly channelled, focused.





As they say, there are some delicacies that are not meant for a pig’s snout. Perhaps this is one of them. I am not used to trying products in this price range, but when I have been able to, I have seen why they are so expensive. I haven’t had that feeling with Helios. Lately, I have been reviewing IEMS that cost 4 times less, whose performance is excellent compared to the price/performance ratio of the Helios. Apart from the treble, analytical ability and tuning, I can’t find anything so excellent that I would recommend them with my eyes closed. Are the Helios good? Yes, undoubtedly. But why use a BA for bass when there are outstanding DDs for this range, which clearly surpass what this product offers? Another thing I wanted to find is a more realistic sound. In my opinion, an analytical sound that crosses the barrier of superior quality is found when it merges with naturalness. This is not the case here either. Although the level of detail is quite high, I don’t find it differentially superior to others in my humble collection, not even to the memory of other IEMS in the same league, which I was able to test in the past. Perhaps my memory is weak, but there are other conflicting drawbacks to this model, such as the difficulty of pairing with my usual sources, the presence of parasitics and noise that I have encountered. It is possible that to move this model, a source to match it is necessary. But this is contrary to the FLAT technology used in this model. I can’t forget about the packaging either, the leather box looks like an additional accessory, which on top of that is small. The metal box is very heavy and the accessories are few, if you compare them, for example, with the Dunu Falcon Pro. Who can tell which is the expensive one and which is the cheap one? Yes, because the external design is not spectacular either, but I don’t really care if the sound is up to the mark.
I don’t intend to be critical of this model out of cliché, snobbery or to differentiate myself from the others. I just think what would have happened if I had bought this model for 1099$, instead of testing it on a tour. I’m sure that after having tested it in every possible way, my disenchantment would have been greater and I would still be trying to look for the positive side. Fortunately, I don’t have to do that here.



Sources Used During the Analysis


  • Xiaomi Redmi Note 8 Pro
  • Tempotec Variations V1-A
  • Tempotec Sonata E44.
  • Earmen Sparrow.
  • Earmen TR-Amp.
  • Hidizs DH80S.
  • Hidizs S9 Pro.
  • E1DA #9038D.
  • Qudelix-5K.
  • Burson Audio Playmate.
  • S.M.S.L Sanskrit 10th MKII + iFi ZEN CAN.