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.
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
