I'll say it right off the bat since the $350 price range is where most people recommend either the Sennheiser HD 600/650 or HIFIMAN Sundara (2020). I have only tested one of those, and the HD 650 in the HD 6XX is really not a direct comparison to the HarmonicDyne Zeus. If anything, I can definitely see a world where a customer has both of these to cater to different use cases. Anyone stuck in mid-fi hell will know what I am talking about. But I will maintain that this $350 price range is also where you get some of the very best headphones from a value perspective, and having the HarmonicDyne Zeus in your portfolio will not change that perspective. There is a lot this set gets right, beginning with the premium unboxing experience with that hard case and serial number badge that oozes $$$, before this set is taken out to marvel at the striking ear-cup design using walnut wood in a fairly gracious manner for open-back headphones. The deliberate tuning achieves a lot of what it sets out to do, and I was surprised by the incredibly wide soundstage even as someone who loves open-back headphones. I wish I had the Sennheiser HD 800S to compare against, but the HarmonicDyne Zeus has the widest soundstage of any set I have on hand physically anyway.

Then there are things that don't meet expectations, be it my own or those set forth by marketing. There are several companies that are just using Beryllium drivers to get sales from those who believe in it, and this is unfortunately a case of HarmonicDyne misleading potential buyers by not clarifying that the diaphragm in these 50 mm dynamic drivers is beryllium-coated at best, and I doubt it's a thick coating at that. For instance, I didn't get the sense of speed and slam I associate with pure Beryllium driver headphones and IEMs. Secondly, there is no way a $350 set can afford to have Beryllium drivers given how expensive they are relative to typical mylar. Then there's the cable that is an over-engineered and poorly executed example of what to do and not to do, which is a shame unless you have a source with a 4.4 mm connector. Thankfully, the cable can be replaced easily, and most of the headphone composition is in fact user-friendly, for repairs and modding alike.

I like that HarmonicDyne has made a clear design language choice for its headphones, with subtle improvements as one moves from the least expensive Helios to the recently released most expensive Poseidon, which we will get to in due time (spoiler alert: I'd pick the Zeus). But the saga from the P.D.1 continues here, with a product that has some excellent accessories for the money being let down by the actual listening experience. The tuning is not a dealbreaker by itself, especially since I know many people first-hand who would like the warm tuning. I will also give credit to HarmonicDyne for some clever tuning and engineering choices. The problem is that some of these strengths are brought down by accompanying items that should have been complimentary. For example, with that incredibly wide soundstage and a fairly controlled treble tuning, I'd like to use this set with orchestral or jazz music, but then the pinna gain compensation is pegged down slightly, imaging is somewhat hazy, and instrument separation could certainly be improved upon, which actually makes this set less viable for those music genres. You need to be aware of the specific strengths and weaknesses of the HarmonicDyne Zeus, and I'd say a $300 price would be fairly attractive for the entire package. $350, which it currently goes for if not on sale, is a tougher sale, one that needs justification on various fronts.