[milosolo]

The HD650 are great IF you pair them with a powerful amp. For final tuning replace the stock cable. Bass is deep and tight, solid mids, and slightly recessed top. I prefer a slightly recessed top to something forward and bright because it is less fatiguing especially for extended listening sessions. The ATH-M50 is another HP to consider. It's easy to drive and has solid bass. The Ultrsones also fall into this category.

 

[c64]

You need closed cans I have never gone back to open cans after experiencing good closed sound, more bass more impact more detail just better in every way and sennheiser are one of the most overrated brands going imo.It's almost like people make good things up about them to justify their cost I know someone who prefers his closed goldring ns1000 £50 can to his sennheiser hd600/hd650/dt770.

 

[NotJeffBuckley]

None of the Pro or Premium Beyers are easy to power. Check out that sensitivity rating... The driver impedance just changes in which specific way they're difficult to get volume out of. 32ohm, they'll suck up plenty of current but you've got a lot of mass to move... 250ohm, require less current but still massive and low-sensitivity drivers... 600ohm, requires even less current but now you better be pushing some serious voltage (and despite the extremely small difference, the driver mass of the 250 and 600ohm versions really aren't that far apart, in my experience it's sort of 6 of one, half dozen of the other, they sound the same to me when powered adequately - the 250ohm is my favorite driver because it's shared between the Premium and Pro line, so can be had for a better value, with a superior headband design in the bargain!)

 

[zero7525]

IMO, pushing out all of the technicalities aside, the 32 ohm Beyer DT880 sounds just fine out of my Cowon.
Though, I surely recommend an amp for the final touch.
These "you can't drive them" horror stories aren't as dramatic as people think of them to be.  

 

[NotJeffBuckley]

I've run DT-990s 250ohm out of a laptop with a pretty crappy onboard sound card and it "worked," but at higher volumes the bass got audibly distorted. I don't listen at high volumes generally, but compare their sensitivity to other headphones and pair it with their impedance... I don't think it's a horror story to note an extremely testable issue. Distortion is introduced when the waveform can't be replicated accurately due to improper power.
 
It's not a good idea to "push technical issues aside;" probably the 32-ohm version sound better because they're less likely to be quite as badly mismatched with the output source even if it's not intended to drive difficult little speakers