Absolutely love these. Been using them for a few weeks now and they grow on me more and more. They make me think of a dynamic driver FT1 Pro; I had the FT1 Pro for a couple of months, but I never really liked them. Turns out planar drivers just aren't for me - I find them too artificial sounding. These a/550 remind me of those but with a far more natural and organic sound, with a more natural decay and separation.

The headphones I've been using for the last couple of years have been the HD560s, and the a/550 I feel are a big upgrade in most areas. They sound (to me) much more technically capable, with cleaner separation, a much larger soundstage and better detail retrieval. I'm also surprised at the amount of bass these put out. Reviews had me expecting basically the KSC75 on headband but in a more premium design. But these are entirely their own thing. They aren't really comparable to any of Koss's budget offerings - they're just a straight up premium audiophile headphone.

Zeos's (YouTube reviewer) review did point out one thing that I definitely agree with, which is that these can sound like a very good pair of speakers. These manage that more than any other set of headphones I've used. Quite often I'll just find myself watching and listening to something as though I'm listening to speakers rather than headphones, which is brilliant for things like single player games, or movies. You really do get the sense that the sound is in the room with you, rather than coming from headphones

Overall 10/10. Really love these and can't personally think of anything that I'd change

great build quality, great comfort. tuned ok out of the box, good amount of bass, very good amount of clarity and detail. these take eq and scale very well. a quick eq adjustment and these are one of the better sounding pairs i own despite owning things much more expensive.

only downsides that are minor in my opinion are they are slightly harder to drive and require a decent amount of power. my second complaint is the cable which i would immediately replace except a different cable with the same configuration is impossible to find.

overall great headphone, very happy.

I’ve had my A/550 for a little over a month now and it has quickly become my favorite headphone, even dethroning my HD650. First of all, the build on this headphone is one of the most premium designs at this price point. The amount of detail Koss put into every inch of this thing is unreal. From the small L&R metal indicators on the fork to the 1958 under the magnetic cushions and the red and blue matching dots on the cord, it just makes my other Sony and Sennheiser headphones feel like cheap plastic. On to the sound. IMO A/550 sounds very close to the HD650 but where A/550 pulls ahead is it’s far superior mid bass and upper mids just have more transparency. That might not sound like a lot but I listen to a lot of bass heady music and rock and I can tell a distinct difference > the HD650. This is by far the best looking, best sounding headphone Koss has ever made by miles, but it’s also one of the best headphones at this price point imo you can get, and Koss has a lifetime warranty which made this an even easier buy. If you’re on the fence, just pull the trigger because this thing brings me so much in a way very few other headphones have.

Sublime sound and comfort, backed by a solid lifetime warranty. It would be nice if they offered a longer cable option and / or a microphone cable for phone usage.

It might become yet another secret of the budget audiophile scene, but I hope it doesn't! Absolutely superb soundstage and tonal balance, quality fit and finish, and shockingly comfortably to wear, not to mention developed just a handful of miles from my house. I'm going to recommend these to everyone.