Disclaimer: Dan asked me to provide feedback on a few AFO prototype headphones during the development process. He was really great to work with and receptive to feedback, and I do genuinely believe he's put out a great headphone. Regardless, I may have some biases because of my involvement. I will try to get right down to it when talking about the AEON Flow Open (aka AFO), but we know I'll ramble on regardless. The fact of the matter is that I think it sounds really good, and I don't hear a whole lot wrong with it. In that regard, there's just not much to say. But I will say things regardless! I can start, though, by saying the AFO is tuned somewhat in the same vein as the Sennheiser HD600/650, the Creative Aurvana Live or E-MU variants, the PMx2, or perhaps even the Eikon/Atticus in a sense. None of these headphones sound exactly alike, but they all kind of have a similar vibe going on (warmer sort of neutral, maybe a bit bass heavy, but generally balanced, not bright, and not screwed up sounding - balanced in their own ways). The AFO sounds to me like a bit of a departure from the Ether line or the closed AEON model. The AFO comes with three types of front damping you can experiment with: a foam piece, as included with the closed AEON, and two pairs of white felt pads. The white felt pads are very similar sounding, but one makes the headphone just a bit darker and smoother than the other. The felt pads have either one or two small notches cut out at the top, with the two-notched pair being the slightly darker-tuned one. I'm glad Dan provides tuning options. They are not too numerous, incredibly easy to install (don't even need to remove pads), and I found it pretty easy to find what I liked the best in a short time. They also don't dull the sound too much to my ears, or, in other words, they don't make things sound dead for the sake of tone. Without any extra front damping, the AFO is honestly listenable to my ears, but not my preference. The upper-midrange has a hot spot that sounds a bit screechy, and the treble is a bit too bright and present relative to my tastes. Still, I didn't find myself cringing or wincing, but I also didn't want to stick with that long. So, I moved on. I imagine some will like this sound, just like some like the HD600, while I find it too hot in the upper-mids. Since the AFO has these options, I won't dwell and beat on how the AFO sounds without using additional front damping. Others can chime in with their own thoughts and preferences to fill out the whole picture. I have not yet tried the foam inserts, but I did go for the white felt pads. I tried the one notch version, liked what it did, but wanted just a hair more. The two notch version seemed to do the trick - subtle over the other, but just enough. (The inclusion of two very similar felt pads may be overkill and too much for some users, but those of us that are picky will appreciate the granularity this offers.) So, with the two notch, felt pads inserted over the drivers, the AFO just sounds...pretty balanced to me. In this config, here is how I hear the AFO relative to my modded HD650 (which honestly needs new pads and may be warmer sounding than is usual): - Switching from AFO to HD650 makes the HD650 sound somewhat dull, soft, and veiled in the treble, with less "pop." But the HD650 still edges it out in sheer smoothness and coherency, which I'm not sure any headphone tops. The AFO manages to sound livelier and a bit brighter in the treble, crisper and sharper, without overdoing it. Of course, once I acclimated to the HD650, the AFO sounded a bit exaggerated at first. So, it goes both ways, depending on your starting point. - The upper-midrange on the AFO is a bit more pronounced relative to the HD650. The AFO can sound a bit more rough around the edges, but this is again relative to the HD650. Despite that, the AFO made distorted guitars and the like sound rather vivid. Otherwise, they have a very similar midrange curve below 1KHz or so. The upper-midrange on the AFO, after I added front damping, was well within my comfort zone. - Bass on the AFO sounds nice and strong. Tastefully emphasized much like the HD650, but with a little better extension, and a little cleaner overall, i.e. less of that HD650 sort of woolly bass. - Similar to the above, even with the strongest available front damping, I still found the AFO to sound powerful and dynamic, top-to-bottom. It was engaging to listen to. - AFO is a little more forward and aggressive sounding, but it still has decent staging and air, even if it's not quite as open sounding as the HD650. But the HD650 can be somewhat laid-back at times. Thankfully, the AFO seems to minimize or eliminate the sort of odd staging I think plagues many planar headphones. Anything panning from channel to channel sounds continuous on the AFO, but sits closer to your face than on the HD650. It's possible some may find the AFO too forward sounding, but I don't mind. I also don't mind expansive, super-3D sounding headphones, so I'm less picky here. - Resolution seems good on the AFO. It picks up minor details on my test tracks. Jury is still out on if it resolves the same "plankton" and "krill" as the HD650, but it does well enough that I'm not particularly concerned. (Update: Further listening on various amps make me think the HD650 may just be a hair more resolving, but I think still puts the AFO in an impressive position. And some may prefer the crisper, less veiled sound of the AFO over the HD650, or perhaps prefer it due to cleaner bass. I think either approach is sensible.) So, really, it's not quite as smooth and cohesive as the HD650 (nothing is, though), and some may find it too forward, but it also seems to break through the HD650's veil, brings somewhat better bass to the table, and can sound a bit more lively and vivid at times within the confines of sounding really balanced and non-fatiguing. The AFO also sounds good at lower volumes. But it does like powerful amps, as it sounded a bit thin from my phone and couldn't always get loud enough for me. What ultimately matters to me is that I just want to put on a pair of headphones and have everything simply work together within my taste boundaries. When that happens, I just enjoy my listening and leave it at that. A/Bing headphones can throw that off, of course, so I'm not talking about that so much. Anyway, there are very few headphones that do that, like the HD650, certain iterations of the PMx2, and similar. The AFO so far seems to fit that criteria as well. That alone is about as good of an endorsement as I can give. It's a very small group of headphones that pull this off. I know I've been blunt and harsh plenty of times about MrSpeakers products (still can't believe I listened to the Ether C with zero front damping and had no idea that wasn't its stock config for a day or two...), and I know many in this community are hesitant about the brand for a variety of valid reasons. I get it, and I won't beat that dead horse here. Dan, reached out to me, and I see that as a step of good will of sorts, which I won't turn down! But I cannot deny that this is easily the best MrSpeakers headphone I've heard to date, to my ears and tastes, and one I genuinely really, really enjoy so far.