Pros: Detail, Dynamic Range, Cleaness, Spatiality, transient
Cons: Need a good amp
I like my HD650. I have always liked the Sennheiser sonic signature and I was immediately impressed after using the HD555 for a couple of years
But then after awhile; after some A/B comparisons I heard the famous HD650 veil. There seemed to be less treble response than the HD555. Yes there was definitely more detail and Bass, but after A/Bing with the HD555, I became a bit annoyed. My parents have a cheap triple port headphone amp connected to the TV for $40. When I connected the HD650 to it, there was no treble response. This is where impedance matching is really important and something, that most people who dis the Sonic Veil of the HD650 don't understand.
So i decided to buy a Class A amp from Firestone (as we don't have much choice in Australia) , the Libby, and the veil disappeared. In fact now they sound bright.
So now I really enjoy them. I do connect them to my Fubar III (Class A/B) occasionally and can hear the dullness returning, even with the high impedance setting. I dont think I need to replace the stock cable as they are bright enough as it is. I would rather use that money to purchase the HD800 or an AKG.
I really personally believe that the veil became an urban legend because people were or are hooking up to either poor amps or no headphone amp at all. I read quite regularly on these forums that people say that headphone amps are useless, but if you really want decent sound and spend a fair but on headphones you really need to get an amp.
I like the sound of open headphones because I live in a quiet area and don't need to isolate the sound. The headphones are extremely transient.
I dont regret buying them at all