HD 600

Superb sound, nice, light and great quality.

I am quite pleased with these. My only complaint is that they don't have an inline volume control. The blue marble design is old & cheesey looking. As others have said Sennheisers fit tight but gradually become more comfortable. They are designed for home use which is why I purchased them. I compared these to several other sets of open phones. First was the Sennheiser 650's. As many said, they seem to have a veil that darkens the sound somewhat. The 600's do not.
A positive and a negative: These really make all the instruments , especially when listening to classical. Each instrument stands out. Sometimes I just have to refocus on the whole composition.
It has been over 6 months since i purchased these headphones so all my mental notes have somewhat faded. Still love them.

If you like music, especially instrumentals / vocals you will love these. If you have never had a solid pair of headphones, you will love these. I personally believe anyone who enjoys music, should have a pair of good headphones like these.
I originally had a pair of vmoda mx-100 which are also pretty stellar, but the bass can be exhausting, and so can the heat buildup. I think of the hd600 like a classic timeless piece. not flashy but so solid everywhere to the point that it stands out. songs will sound different than you've heard them before.
2 things I don't love, the proprietary connectors to the headphone, and sometimes i notice the clamping strength on side of head, but definitely not a deal breaker.

I got these headphones headphones two weeks ago and I can say they are easily my favorite headphones by far. I've never been an audiophile I've always gone with what's comfortable Bose qc25s, Sony WH1000XM3, etc. I got my Sony's and loved them for 5 months then got tinnitus long story short it made using the headphones awful and all closed back headphones seemed to make it worse. So after doing research I decided to get these so I can use headphones again and I love them more than my sonys. I honestly forget they're on my head 90% of the time, it had clamping issues for like a day but then it went away, and the audio quality is amazing.

Very good sound but I have slight preference for Hifiman HE-400i. Headphones are ear of the beholder though - what one person likes another dislikes. See reviews before buying - these are classic headphones. They are very well constructed and look like they will last a long time.

Great clear sound across the spectrum, making it great for mixing, but has a lot of strings attached. The cable is super long and super wimpy. In the manual they recommend "buying an upgrade cable to get the most out of your headphones". That cable costs around $200. For a cable....
Within the first week, the left ear started buzzing on low bass sounds. Googled it and it turns out that hairs can get on the driver. Ok. Hair...my only weakness...lol. I had to use a can of compressed air to get the hair off.
Good sound, but feel like I'm entering into a high-maintenance relationship with a bunch of "gotcha" price grabs along the way. I'm keeping them in their box and only using them when I need critical mixing ears. Otherwise, I'm using my Tascam TH-02. Cheap, but built like a tank. There's a lot of hype with the HD600s and the price fluctuates irrationally, indicative of the hype-induced markup. Still, really good sound, but needs to be a better product. It's like having a really good hammer head on a rubber handle. Makes no sense. Build it better.
Also, it sounded terrible plugged straight into the iMac and portable CD player. Once I plugged it into my Apogee Ensemble, it sounded great. Just be aware. High-maintenance. Not an everyday set of cans. Would only recommend them if you need to mix. Really good at finding resonances and at hearing all the instruments across the spectrum.

Update: Before buying these, you must check out the Sennheiser HD58X Jubilee. I wrote a thorough review comparing HD58X to HD600 for mainstream music, jazz, classical, and opera lovers schziv.wixsite.com/hd58xvshd600?
Incredible. I had the Sennheiser HD598 for 2 years which are supposed to be terrific. I did not like them at all and avoided using them because something about the sound was irritating, like going to a concert and listening from behind a curtain. The HD 600 completely correct this flaw. Bass heads - these are not for you. I enjoy my deep bass, but I gladly give up the extra oomph for clarity. These are exactly that.
Despite all the myths about needing an amp to listen to HD 600... totally false. If you want to blast rock or pop, yeah you will need extra power. But opera, classical, jazz these will drive amazingly right out of the iphone. If you want proof go watch Clavinetjunkies binaural blind test between HD600 w/ and w/o and amp.

Worked Well

These give you the music without embellishments - no enhanced bass, no screechy trebles, just what's there. These are more analytical in their delivery. If you're looking for a bit more substantial bass, go for the 650's. All of the Sennheisers I've tried so far are very comfortable and feel light, and I could wear them for hours. They are open backed but you have to have it cranked a bit for others to hear a ways from you, but if you're going to be in close quarters with others, get closed backed ones. As mentioned elsewhere, the soundstage is pretty much confined to between your ears with a little bit of imaging appearing outwards, which is wide enough for me; you do hear above and below you too (how do they do that?). Imaging is solid and stable. I enjoy these more than the 650's which added an unnatural amount of bass for my tastes.I've seen that some people complain about too much clamping pressure on the ears but I have a small head so they work just fine for me. Included is a 1/4 inch removable jack on on the end which won't fit any other wire but another adapter will fit on the 3.5mm jack underneath if you lose this one. You won't get a whole lot of volume out of these if you plug them into your phone (with the right adapters), but it will work - you'll need a separate headphone amp for real volume, however. I can get a listenable volume out of my iPhone 8s but that's all.