I own around 8-10 different headphones and earphones that range in brands, price, styles, etc... I’ve tried Klipsch, Bose, Sennheiser, V-Moda, Audio Technica, Beats, Apple, AKG, Samsung, Sony, Skullcandy, etc... I do enjoy listening to a large variety of music and I do like premium headphones but I am in no way an audiophile. The brand I always seem to go back to for more has always been Sennheiser. It all started with the HD558 open back headphones. It was my first experience with open back headphones and I really liked it. I found myself hearing so much more than I had ever heard in my favorite music. Now after using the HD650 for a while I feel I can offer a decent impression for someone considering purchasing these headphones.While many people will surely disagree(audiophiles I’m looking at you), you can technically drive these headphones with your phone or mobile music device. It does have 300ohm impedance, but the sensitivity of the drivers is such that you can get enough volume to “hear” music. It is almost loud enough and I imagine for many people it will be enough. However, the HD650 may as well be a cheaper pair of headphones if all you’re going to do is plug these into your phones because the listening experience takes off when these cans are driven properly. Whereas you can hear music through them on your phone you can actually listen to music when you have these driven.My setup is fairly simple and somewhat low end still. In fact I imagine that I haven’t had a chance to fully appreciate my headphones yet. I am using the Schiit Fulla 2 DAC/Amp and plugging in my iPhone 7 Plus with the camera adapter through usb into the Fulla 2 and have listened to lower quality music files, Apple Music 256kbps, and Tidal lossless 1.4Mbps files. While there are a lot of entry level DAC/Amp or Amp solutions I think the Fulla 2 is excellent in its quality, power, ease of use, and options.The build quality is good and while it does use a lot of plastic it feels durable. What I really appreciate about Sennheiser and specifically these headphones is that while everything feels durable it is also all replaceable. You can replace the headband, the head cushion, the ear pads, the cable, and you can order it all from Sennheiser directly. I like owning a product that I know I can maintain and I appreciate not having to send it to Sennheiser to fix every little thing. I have owned a lot of headphones that use cheap plastic that cracks, pleather that flakes and peels, and rubber coatings that wear and get sticky. Then you call the companies and they either don’t make the parts at all or used to but don’t anymore because they don’t make the product any longer. The design of the HD650 has been used from at least the HD600 and longer than most millennials have been alive. In fact they kept the tried an true design for their new HD660s so they’ll have parts for years to come.Speaking of tried and true, they are that way because for one the design has worked acoustically for them but also the design has led to one of the most comfortable headphones ever made. They can take an adjustment period and for people with big heads like myself, I recommend fully extending the earpieces and flexing the metal band the relax the clamp force on your head. There are instructions online for how to do this safely or you could always stretch them out over a box to loosen them up a bit. If the clamp is too strong or not either way you’ll end up with a very nice and comfortable fit. The ear pads are a nice velour material and the foam is appropriately soft and spongy. The head cushion is a very silky material and the foam is very soft. I really like that it has a small gap right at the top of your head to prevent that from being a hot spot of discomfort right on all of the blood flow in that area. After working my set in I find them easily wearable for hours and hours without discomfort although the ear pads can get a little warm if you’re in a hot area. After putting them on your head I recommend just tweaking the rotation of the ear cups until they feel right.In my experience with these headphones I have been very impressed. In fact it may be the most enjoyable music listening experience I’ve ever had. The HD650 is described as the most colorful in the HD6 line but compared to most of the headphones I have used before, it comes off as pretty neutral and well balanced. The mids are a bit forward compared to the lows and highs but it feels natural to my ears. It is a warmer, darker, slower, and thicker experience but it’s smooth and rich. I know it sounds like I’m describing eating dark chocolate but it is a bit like Dark chocolate for your ears. The level of detail is great and it is just very easy on the ears. I enjoy listening to music on my HD650’s and I actually do so more than anything else so far. If you’re looking for bass, I’d keep looking. These are open back headphones and while the bass is very nice and well defined they are not gonna punch you in the face like a bass head would like.Comparing them to my HD700’s I would recommend getting these because while the HD700 is maybe technically a better headphone it is sometimes too analytical and the spikes in the high end can make listening to them a little tiring. If you just wanted to listen to classical music then the HD700’s are amazing and better than the HD650 in my opinion but overall the HD650’s feel more versatile and more enjoyable for all types of music.If I had to make any complaints about the HD650 it would have to be the wire connections and the stiffness of the adjustment on the ear cups. The headphones were nice enough to put the Braille letter L on the left side but the cable has no such thing. The connection point is a two prong termination that has to go a specific way on a specific side. They do have a small raised L and R respectively on each side and the raised letters are meant to face outward. The problem is seeing and feeling the raised letters to tell which is which. If you’re in good light and have decent vision then it is easy enough to see. However if lighting isn’t great and/or your vision isn’t perfect you’ll have a hard time telling which is which. To make matters worse you can potentially damage the cable termination or the headphones if you plug them in incorrectly. The three bump Braille “L” on the left side would have been an easy solution to this, especially considering they’ve already used it on the ear cups.Another issue is the stiffness of the adjustment band. Sizing these headphones perfectly is required for maximum comfort. You ideally want both sides to be more or less equal lengths and to the right position so the headband isn’t putting too much pressure on your head and the ear cups sit well over your ears. Trying to adjust the headband is a bit of an inconvenience because to start with it is stiff and hard to pull out one click at a time. The best way to do this is to grab the metal portion towards the ear cup and pull away from the headband. Also there are no markers indicating the adjustment so you can’t be quite sure if both sides are equal or in the right spot until you put them on and then resize them. Another minor gripe but something that seems easy to address.I feel the HD650 is around or just past entry level audiophile headphones. If you’re looking to upgrade to these from something like a HD558 or 598 I would say go to an audio store that can provide you with a burned in set of headphones with good quality DAC/Amp and the listen to the kind of music you like. Considering these really only come alive with the right equipment driving them I think testing these out beforehand is the only way to go. Also, if you really do like these headphones the HD6XX from Massdrop have come around 3 times or so for $200. They are basically the HD650 rebranded and selling for $200 and I think that’s a steal.The HD650’s might change the way you feel about music. They might allow you to explore songs you’ve heard hundreds of times but in ways you never knew. They also may not do any of that for you, but if you appreciate music I think you just might appreciate these too.