Apparently Ra97or has cornered the market on opinions of what is or isn't "fast", but nonetheless, I'll throw out a vote for the Beyerdynamic T1s. No clue what would be considered the fastest headphone out there, but the T1 is easily the fastest headphone I have heard and/or own. Supposedly the Tesla driver is very light and efficient, and it sure sounds great to my ears. Although the presentation is obviously different between speakers and headphones, I tend to really appreciate some of the sonic qualities that are inherent to my Magnepans. I can certainly understand why Zazex mentioned the Grados. I have the 325s and the 80s, and much like my Magnpans they just allow the music to take on a very organic and unencumbered quality. They seem less like transducers are more like transporters that take you to the venue of the performance. That's why so many of us who appreciate Grados get excited over live albums. I think measurements are a valuable tool in this hobby, and I'm always interested to further my knowledge and understanding of them, but the judge and jury will always be the two funny looking things attached to the sides of my head. All I know is that Maggies, Grados, and the Beyer T1s sure sound darn good to me.