Sound quality: 9/10Comfort: 10/10Build quality: 10/10Battery life: 9+/10 (after a week I still haven’t run out of battery yet!)Comparison models: a quick comparison list of headphones I’m comparing these to.Bluetooth features: 10/10Sound quality. These headphones have a bit of a slant towards bass. Not a boomy bass but a more rich bass response than I anticipated. One of my big concerns with any headphones is distortion. I work in video production and motion graphics, I spend a good 40% of my workflow dealing with audio in some fashion on my timelines. I also come from a strong audio editing background—working in recording studios, broadcast radio stations, and playing in several bands on instruments. I play bass and I absolutely the fidelity of these headphones so far. The bass is rich and much more true to the way it sounds without having headphones on. I think I most enjoy the listening experience on these headphones with noise cancelling turned OFF. Why, I think I just like being able to hear things around me when listening to music—makes me feel more like I’m in a band playing rather than recording in a studio that is dead quiet.Now let’s talk about comfort. These are pretty good sized headphones. They are comfortable to wear. They do get warm but not as hot as other (very well known) brands. After working in studios where the headphones had to come off after every take, these are a welcome change. I can leave these on for quite a while and not get uncomfortable. An hour is pretty easy. I usually don’t leave them on that long because I go a little nuts when I’m editing and like to take frequent ear and eye breaks… regardless they are comfortable. 

Build quality. These feel like they will last a while. I really can’t give much of an assessment on the length of time these things will last until I use them for a long enough time. My only assessment here is on perceived quality and the way they feel and the materials used. Carbon fiber should last for a long time. The carbon fiber also has the added benefit of really making these things look better than other products at a similar price point.Battery life. At this point I feel like I should talk about the battery life. I know that the advertising for these is a 43hrs battery life. All I know is that you get the cord that comes with the headphones and use a standard power block to charge them up. It’s been a solid week so far and I’ve not had to recharge them at all. Also, I discovered something interesting, the literature talks about using the AUX cable (supplied) to listen to music with noise cancelling turned on giving about 52hrs of battery time. I used the Aux cable and never even turned the headphones on for a while. In theory they shouldn’t be using any battery when not turned on, right? I would *guess* that these are able to be used as “passive” headphones indefinitely. They sound great in this mode, by the way, and as I’ve already said is my favorite mode to use these headphones. To be completely transparent here, I plan on coming back to this review every 6 months or so to make assessments of the battery life itself.Comparison models: Audio Technica ATH-M50x (proprietary cord=boo! ;reliability=great; comfort=5/10)Audio Technica ATH-R70x (proprietary cord=boo! ; reliability=awesome!; comfort=8/10; a great set of headphones but you have to pay an additional $100) 
AKG K371 (build quality=5/10; isolation=meh; sound leaks on these things; these things begin to fall apart after a year or of use)Beyerdynamic DT1770 (Sound quality=10; build quality=9/10; Price point is $450 and up though)Hands down the Phiaton 900 legacy headphones are the way to go at this price point!Bluetooth features. After using these things for a while I stumbled upon something that I missed when reading the illustrations that came with it. They are touch controlled. The right side outer surface allows you to turn up what you are hearing with a simple swipe up. Double tap to pause. Swipe forward to go to the next song and swipe back to restart that song you are on. Kinda cool. I use the volume up and down on the side all of the time because… well I don’t know—habit.Pairing with a device is super easy. Simply put it in the pairing mode and then find it on your device—done.These are set up for accepting phone calls too. In case you are wondering these are really just headphones, but there are microphones on the headset that are (technically) there for the noise reduction to work. [The mics pick up the sound around you that need to be reduced and when the noise reduction is turned on, you get a very nice result.] They basically are using those to work as the mics that pick up your voice. In my tests they work great with my iPhone (Xr) and my iPad (ver 3), and my MacBook Pro (2019). They don’t work with Zoom on my (2013 MacPro). I think it’s probably because the bluetooth is too old on that computer for whatever version of bluetooth these headphones are using. You can hear the zoom calls really well with them; but, I can’t get the mic to work as an input on that computer. So, you might consider how old your bluetooth devices is that you plan on using with these.Bluetooth signal. I’m impressed with these things. I haven’t lost the signal at all in my normal day to day activities. I can go out side with them and continue my conversations without taking my phone with me. I can listen to music while going to check the mail or get something out of my car or whatever, I’m impressed with the range I get out of them.All in all, I feel that these are a great set of headphones.*** UPDATE -- November 2023 ***These things are still a great set of headphones. It's been 2 full years since my first review of them, they're still going strong. I do now wonder if they will have replacement earpads when/if I need them. I don't need them at all---YET. Mine are still in "Excellent -" condition (is that a measurement? Maybe I should say... A- condition? Yeah, that's about right). So, why am I wondering about replacement earpads? Because in my experience I have found that in the long-run headphones just need pad replacements. Nothing is permanent and ear pads will break down at some point. I'm not too clear on how to actually get replacements to them when/if I need them. There is a spot on Phiaton's website that gives the me the toggle but the ones for the 900 legacy have been "sold out" like... forever. Each time I've visited it, they've been "sold out." Maybe they only do small runs? I don't know. So that's what drives my concern.SOUND QUALITY RE-ASSESSED:I've been doing a lot more Quality Control for audio going out of my edits. I've noticed that the bass end of these are bassier than most headphones I gravitate towards... So I tend to calibrate my mixes a bit lighter on the punchy parts of the bass end when I'm using these. On the higher end these headphones are way more detailed than I can accurately describe--so much so I've actually had to re-edit things that I could hear clearly on the headphones that got lost over monitor speakers--1400 Hz/1.4 kHz range typically... I'm guessing that that range is probably dropping off faster in 'open air monitor-speakers places' than it does millimeters from my ears when you're wearing these on your ears... I still say these are very listener-friendly headphones and I'll always gravitate to them for just enjoying music.What am I comparing these to in this update to my review? The usual suspects in studio headphones: ATH-M50x, AKGK240, Sony MDR-7506, some 'really-great-sounding-but-super-cheap-materials-used' Monoprice headphones, and a really, really old pair of Sennheiser's that are aging by the second and were probably used by a T-Rex.These have dropped in price since my purchase and I'm pretty sure that they are being marketed against those Sony 1000xm5 or something like that. But I think they are just marketing these incorrectly. Although these things have really good noise cancellation, I don't think that's their strong suit. These feel great, sound great, are well built, and I love that I can use them wired all day long and never even wonder about their battery life. I choose to listen to these with NC OFF--the closed back design does enough for me. I'll stop typing now because the Beatles - "You know my name (look up the number)" from Past Masters is up next on my playlist and I absolutely LOVE the way that song sounds on these headphones!