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HarmonicDyne Poseidon Headphone Review

Another enters the pantheon

Christopher Coke Updated: Posted:
Hardware Reviews 0

HarmonicDyne has made quite a splash with its over-ear headphones since the original Helios was released in 2020. As we inch ever closer to 2022, it’s back again with a brand new innovation: nickel diaphragm dynamic drivers. With the goal of outperforming the popular beryllium-coated drivers, the HarmonicDyne Poseidon are launching to Kickstarter today for $279 (retail price $435). Let’s take a closer look and see if they’re worth backing in our review. 


  • Current Price: $279 Super Early Bird, $299 Early Bird, $435 Retail (Kickstarter

HarmonicDyne Poseidon - Overview and Unboxing

The HarmonicDyne Poseidon are one of the most exciting headphones of the year. I reviewed the Zeus, the Poseidon’s predecessor back in January, and was impressed on multiple levels. Poseidon brings back much of what I loved on that headphone but implements a new nickel-coated dynamic driver and a beautiful new look.

Diamond-like carbon. Carbon nanotube. Beryllium-coated. Pure beryllium. We’ve heard of lots of different types of drivers, but nickel is a new one. In my research, I couldn’t find another headphone that uses it. Could this be the first? Here’s what HarmonicDyne has to say about their choice to use pure nickel coating versus the more common (but still exceptional) beryllium:

While beryllium has been hailed as the king of diaphragm materials so far, the molecular composition of nickel proves to be a much superior metal for the conductance of sound. With four times the density and more than double the tensile strength of beryllium, purified nickel is a much stiffer and responsive diaphragm material, allowing greater clarity and articulation with reduced distortion in the low frequencies.

While I’m no engineer, HarmonicDyne seems to be onto something here. I’ll go into further depth in the listening section, but in a side-by-side test with the Zeus (which uses a beryllium driver), there is an immediate jump in crispness and clarity. How much of that is due to the tuning and how much is due to the driver is up for debate, but I can certainly say there’s a bump in sound quality that reveals more details in your music and games.

Like the Zeus, the Poseidon arrives in a locking hardback case. The headphones ship safely in a custom foam cutout, accompanied by the cables in a velvet bag in their own cutout. The packaging here is similar but feels more bespoke than the Zeus and definitely makes it feel like a higher quality package than its price would indicate.

The headphones again feature HarmonicDyne’s iconic wood and stainless steel construction. Compared to the rich, dark walnut of the Zeus, the Poseidon uses blonde maple on its earcups and headband. The stainless steel is now black instead of silver, which creates a beautiful contrast that makes the headphones look really beautiful. The choice of material also affects the sound profile, as wood density directly impacts the reflection of sound waves and how sound presents (which is why “tonewood” is so important in acoustic guitars). Maple is a brighter tonewood, which is audible in the sound compared to the Zeus (but this is still a warm headphone overall).

The grills are once again the star of the show in aesthetics. They’re laser-cut with an intricate pattern that’s absolutely stunning. The level of detail and precision is mesmerizing and truly makes these headphones something special in the looks department. HarmonicDyne, if you’re listening, never change. This is truly great work. 

The gimbals and headband slider allow for a wide range of adjustments to achieve a comfortable fit. The earcups can pivot 180-degrees in either direction, so you can lay them flat around your neck when you need a break (pointing them up allows you to keep hearing what you’re listening to). The cups can also spin freely on their hinges, right up until the jacks tap the yoke. These headphones will be a good fit for different head types. 

One of the biggest improvements coming this generation is with the included cables. Like the Zeus, the included cable is balanced and ends in an XLR connection. If you don’t have an XLR amplifier, never fear. HarmonicDyne also includes a 6.35mm (¼-inch) interconnect, which should allow you to connect to most unbalanced amps. Where the Zeus’s cable felt more handmade, this one is beautifully and professionally braided in straight black, matching the metal pieces on the headphone itself. While there was nothing wrong with the old cable, this one just feels much higher quality and a better match for the headphone itself.

The only downside here is that there isn’t a way to connect to smaller 3.5mm connections, like those on most smartphones and PCs. I would recommend using these with an amp (they scale well with power and sound better with extra juice) but it’s possible to run these effectively on more powerful dongle DACs, like the TempoTec Sonata HD or THX Onyx on the pricier end. Connecting to those sources requires a separate adapter, like this one from NewFantasia, which will run another $20 or so.

I also wanted to note that the first cable I received had an issue with a faulty pin. I received an early unit (according to the serial, it was only the seventh off the line), and these things sometimes happen. I reached out to Linsoul and their service replacing this cable was fast and excellent. These headphones come with a full one-year warranty, so should you have any issues, you’ll be able to receive support.

HarmonicDyne Poseidon - Comfort and Fit

The Poseidon is a ridiculously comfortable headphone. At 380 grams, it’s not the lightest in the world, but that doesn’t detract from the experience one iota. The headband balances the weight very well and the cushions are exquisite. They’re plush and covered with a velour-like material. Visually, they look the same as the pads on the Zeus but are softer to the touch. They’ll need to be cleaned more often but are easily removed to hit with the lint roller for dust and stray hairs.

HarmonicDyne Poseidon (left) has softer pads than the HarmonicDyne Zeus (right)

Clamp force balances firmness and comfort well, feeling secure without causing any pain or discomfort. 

HarmonicDyne Poseidon - Sound Impressions

Onto what really matters most: how do these new nickel drivers and maple earcups sound? To test these headphones, I spent hours A/B testing individual tracks with the Zeus. As always, these impressions are largely based on what you’re listening to. For my purposes, I tested through my Post-Hardcore playlist on Spotify, High Quality, using my Xduoo XD-05 Plus. I also mixed in ambient chillstep, Coheed and Cambria acoustic, and listening through NF’s The Search for hip-hop. I also tested their gaming performance in Battlefield V and Call of Duty: Warzone

Starting with tuning, the Poseidon has a definite U-shaped tuning that may tend toward V-shaped. Compared to the Zeus, mid-centric elements like electric guitars aren’t as forward. Male vocals in particular sound intimate, like NF in My Stess, whereas female vocalists like Adele in Set Fire to the Rain, have are smooth and sweet. Bass is fast, tight, detailed, and clearly elevated for punch and to lend body to the music. Highs are rolled off and never sharp, even when they would tend to be on my other go-to headphones, the HIFIMAN Ananda and Sundara. 

Put another way, these headphones are perfect for elevating mainstream music. If you’re a fan of pop, hip hop, and music that puts vocalists first, you will find a lot to love here. They take mainstream music and bring forward the vocalists while revealing details you may not have even realized were there. 

The first thing that stood out to me is that these drivers improve bass resolution. The increased rigidity of the nickel diaphragm allows the headphones to subtly improve the bass texture and detail. The Zeus were no slouches in the bass department, and extend further than the Poseidon, but these definitely inch forward the quality bar. This is especially true when you listen for how well the bass exists alongside everything else in the track. There is zero distortion, bleed, or muddiness. If you told me there was a separate driver handling the lows, I might believe you. 

Mids, on the hand, are definitely stepped back from the Zeus. For driving rock music, key instruments like electric guitars lack their forward edge. They lack little in detail but lack the “wow” factor the Zeus was able to deliver. When moving on from heavy, driving, guitar music, this actually works to the benefit of the Poseidon. This is especially true in Adele’s Set Fire to the Rain, allowing the orchestral elements to create a deep, atmospheric wash that’s more balanced and well-rounded than the Zeus could deliver. 

In Rihanna and Eminem’s Love the Way You Lie, this tuning placed the guitar perfectly — bright, full of detail like you’re in the same room with the player, while the snare snaps popped out on top. Another great listen was Sweetest Girl by Wyclef Jean. The layering and detail was so, so good.

When it comes to highs, percussion hits really come forward. Rolling taps on the high-hats in Tom MacDonald’s Sober complement the kick and bassline well. Cymbals ring with realistic life and decay. The highs are rolled before any sibilance of fatiguing sharpness can set in. There’s a good sense of air to the sound, enhancing the atmosphere. They’re not a high-centric headphone but they deliver lot of detail and realism with their presentation. 

One thing that does feel like a step back from the Zeus is soundstage. These headphones aren’t closed in, but the sense of space isn’t as wide, also falling behind popular planars in this price range like the Sundara. There’s a realistic sense of space for gaming but if you’re looking for the same sense of depth, you’ll find these are more constrained. 

For gaming, these headphones will work well, but I still think I would reach for the Zeus more. The improved soundstage and heightened mids are better for immersion and picking out tiny details that can make a difference in your competitiveness on their field. Still, the differences for gaming aren’t huge, and the bass improvements on the Poseidon are definitely better for cinematic presentation and intense action. I wouldn’t let these differences be the deciding factor if you’re also planning to use these headphones for music.

For my own listening preferences, I find the Poseidon’s are a bit mixed. As a fan of guitar-driven music, the Zeus offer the more energetic, driving listen. At the same time, the added detail of the Poseidon is one of its best features. The first time I sat down to test them, I listened to Pearl of the Stars on the Zeus, switched to the Poseidon, and went back to Zeus and it sounded as if a veil had been dropped over the track. That was a surprise for me and definitely drove the continued A/B testing. It’s not like that on every track, but is especially revealing on acoustic tracks where there’s a lot of detail interplay between the bass and the mids.

Final Thoughts

The TL;DR is that, despite their similarities, the Zeus and Poseidon are actually pretty different headphones in terms of sound signature. The Poseidon is better for mainstream pop and hip-hop. The Zeus is better for rock, but I did find myself missing the added touch of awesome the Poseidon delivers in bass detail. In look and feel, the Poseidon is also a clear winner. At $279 or even $299, these are a steal. If you prefer this tuning, I highly recommend picking up a pair while they’re still at Kickstarter pricing.

Find out more at the HarmonicDyne Poseidon’s Kickstarter campaign page. 

The product described in this article was provided by the manufacturer for evaluation purposes.
  • Beautiful design
  • Improved bass, detailed and punchy
  • Excellent tuning for mainstream music and gaming
  • Hardback case with included (and great) balanced cable
  • Well-priced at $279 or $299
  • Mids more recessed
  • Soundstage is tighter than Zeus


Christopher Coke

Chris cut his teeth on MMOs in the late 90s with text-based MUDs. He’s written about video games for many different sites but has made MMORPG his home since 2013. Today, he acts as Hardware and Technology Editor, lead tech reviewer, and continues to love and write about games every chance he gets. Follow him on Twitter: @GameByNight