I've noticed people definitely differ in regards to the HD 600 and HD 650. Some say they are similar and others like myself found them quite different. I preferred the HD 650 but found things I liked more about the HD 600. Honestly both bother me a bit, so I'm rather neutral on them but honestly feel both are a bit overrated. 

Since you have such positive opinions of the HD 600 (which has, what, 2dB less bass?), I can only really conclude you just wanted to break a 12 year long chain of 3+ star reviews, like a kid kicking down a sandcastle.

@PaulWilson
I'm sorry you feel that way, but I feel that with you joining the forum today just to make a comment on my review seems impulsive, and that your understanding of my criticisms is really superficial.
 
As we can see from this graph: http://tinyurl.com/600vs650 , the HD600 and HD650 differ by about 5db worth of bass up to around 65hz, and after that it tapers down to 1-3db for the bass range and midrange, and stay fairly similar to each other until the 2500hz range, where they begin to starkly contrast again, with the HD650 having more peaks and more present upper mids and treble.
 
They should be fairly similar as they're based on the same driver. However, as most people here can attest, the FR of the driver alone is hardly the sole determining factor of what makes a headphone sound the way it does. If that were the case, why would Sennheiser even have come out with the HD650? The imaging and sound staging of the HD650 was particularly notable, negatively, compared to the HD600. The HD600 sounded lifelike and intimate while the HD650 sounded distant and dreary, taking away some of the midrange ability from the HD600 which made the increased bass even more noticeable and unwelcome. Additionally, 5db is quite a bit and it was not of the tight, agile type of bass, but the blooming, bloated kind.
 
My utter shock that this headphone still gets the accolades it does today while being a poor representative of modern technology, and of Sennheiser as a company, is all the reason needed to write the review I did. There's no need to make ad-hominem insults as to my motives.

Nah, I also intend to post some reviews of headphones I own. But you're right, it was impulsive, sorry.

@PaulWilson
I really appreciate that. As I stated above, if the HD650 were marketed downstream from the HD600, as an MSRP $199 or $249 headphone, I would lead the charge in suggesting it as a competent, relaxing, dark and warm headphone. But the mythos around it being the greatest thing going from a multi-million dollar international audio research company is what really bothered me. It was Sennheiser's flagship (under $10,000) for almost a decade until the HD700 and HD800 were released and they wanted $499 for it, which is basically equivalent to punishing the consumer for brand loyalty, in my opinion. 

It seems that there is no middle "i kinda liked it" ground with this one, as its "awful" or "my favorite", which tells me that its not one of the better choices around if you are a serious headphone nut looking for your next earfix
Im kinda concerned now that the *new*  Senn 630vb is going to be the next "HD650" as the price is already -$50 off the original street price and yet no one is buying it, and of the 2 reviews you can find if you burn your eyes out trying to find a review on Google, there is one guy who likes it a lot and yet he said it reminds him of the HD650 and the other said it reminds him of the Momentum which i hated......"sigh"<>"arches-eyebrows".

2 stars hahaha, i have no ideas about this fun review =)).

I just wasted 3 minutes of my life reading this "review"...

@cakebreaker It seems like you're posting an emotional reaction after reading a dissenting opinion on a headphone that you personally rank highly in your inventory, instead of entertaining it with an open mind or offering some kind of counter argument. It doesn't take a lot of effort to simply insult, and I'm confused why you'd be taken aback so much for a headphone you've already established as one of your favorites.

Could it be the case you got a dud pair of headphones? I know of no commercially available item that has an absolutely uniform production quality.
 
There will be fluctuations in the quality and measurements of every single part and you may have struck lead when you were expecting gold.

Just wanted to say as a total newbie, the review is still helpful to me as I am considering buying the 600 vs the 650; it helps to read a wide array of opinions.  So far my bias is a little in favor of the 600 since it seems like a "safer" choice since I'm not sure I am looking for a warmer/bassier sound.  I actually do like a warm sound with bass north of neutral, but I already have cans for that and I'm looking for something with as much detail as possible in the $400ish range.  My best headphones so far in that vein are way down the chain, and I rather like them, the HD 558, but wanting the next step up.

I love how he says, "it's a stain on the history of a great company"

Meanwhile it's one of the mostly highly lauded headphones available.

This review has to be a troll job. 

@Mani ATH 87 
 
Confirmation bias is a seductive trap -- it's too easy to read an opinion that disagrees with your own and say "this is a troll", so that you don't have to do any critical thinking or self-doubting. I see you proudly display a pair of HD 650 as your profile picture, so it's pretty clear to see your opinion may be the result of bias.
 
Keep in mind I never said, nor would say, that the HD 650 was a terrible-headphone-full-stop. Marketing is a powerful beast. This headphone was, for a decade or so, marketed as Sennheiser's flagship. Sennheiser is a big name that, in my researched opinion, rested on their laurels. Do you really think when Average-Joe and Average-Jane -- the same people who write the ubiquitous four- and five-star, 20-word-or-less reviews on common websites -- would have purchased dozens of competitive headphones from multiple manufacturers to see if they "made a good choice" in buying the HD 650? Of course not... they hear "big company A has top-shelf product B, and that's what I'm going to buy and I'll be happy with it."
 
But I have compared dozens of headphones and so have other reviewers here. Check out some other critical 3- and 2-star reviews of this headphone here and on other websites. They tend to say similar things to how I feel, and you might just learn something in the process.

I can understand why soundstige reacted they way s/he did.
I felt that they were a bit too bright when I first got them, but they really do need a decent burn-in (100+hrs) for them to get to their engineered sound signature.
It's also important to note that not even sennheiser calls the 650 an "upgrade" from the 600.  It was designed for people who want to feel their music more than they could with the 600.
I think the confusion stems from the mindset the author had when purchasing the headphones and going into the review; saying that buying the hd650 is like a fireworks display.  Instead, one has to realize that headphones like the hd650 are like purchasing a mercedes s-class sedan. It's not a sports-car built for the quarter-mile.  It's meant to make 500 mile rides on poor US highways surprisingly comfortable.

Nice accusation to throw around based on the square root of nothing.  soundstage has no evidence to base his observations on in his post 4/12/16, all I see is supposition of Mr and Mrs Average.  People like what they like and no self appointed experts should think or believe they have the right to tell others they are not right.  You'll be telling us next that vanilla is better than pistachio and green is the only colour people should like.
 
For a self appointed expert your original post/review is full of emotive, subjective language.  You confuse your opinion with fact.  "Why do people like this blah blah...?"  You appear to be one of these people who goes around thinking - why don't people think like me and they're wrong because they don't?  If someone likes these headphones, they're not wrong.  If someone doesn't like them, they're not wrong.  It's only wrong for one side to try and tell the other they're wrong for their personal preferences.
 
Because of your invective, your review reads like someone with an agenda rather than a neutral appraisal of a piece of equipment and when people get that impression, they quickly turn off from anything you might be trying to say.
 
Maybe you should read some of the excellent reviews here on Head Fi and learn something yourself.

I own the hd650 and mind you I have zero bias. I've actually disliked many Sennheiser products. But let me tell you. The hd650 doesn't sound bad. It doesn't have the best detail retrieval, but it does scale pretty well with higher end systems. I mean hey, it's pretty detailed but the new planars and some akg offerings are more resolving for the same money. But that doesn't matter. The balance is so natural. It's also got ZERO fatigue and is all around a pleasing listen. I think it's a damned good headphone.
Gonna have to say this review is pretty troll and I wouldn't take it seriously.

@Uzuzu, not sure why you automatically identify people who disagree with you as "trolls". I gave reasons for all of my opinions which is pretty much the opposite of what a troll would do. Even see here, how you're disagreeing with me, yet I don't think you're a troll? You should try that.

[Mod Comment]
Everyone is entitled to a point of view - but no more comments about trolling OK. Personal attacks are not allowable on this forum!

Funny, i have the exactly opposite view on these Headphones. The 650 is to me the more musical version of the more neutral 600, and a tiny bit more technically capable. BUT i think the 650 has to be feeded with higher gear in order to clealry see the benefits of its extreme musicality.

As compared to the Senn 600s the HD 650s have a bit more resolution and more extension in the Trebles and especially the Bass.
My experience with them, is that i liked them right out of the box more then i ended up liking them over time.
The new Senn 630VB's have a some of the HD650 sound goin' on, but the 630VBs have much better and more natural sounding mids.