Summary: All I can say is, I am glad I purchased these cans! I am not going repeat all of the technical aspects of other excellent reviews but I will add my 2 cents. I researched the HELL out of several brands and types of headphones before taking the leap on the 940s. Being a musician and currently owning the Awesome sounding Shure SE535s, I needed some cans that would the same EXCELLENT music reproduction.
Summary: These headphones should be valued for providing an ultra-bright sound signature not offered by any other headphone that I'm aware of.
Comparisons with the HD800: If you compare the 30hz and 300hz square wave measurements from the innerfidelity charts between these and the Sennheiser HD800, you'll see that the two are almost identical. I own the HD800s and this, and I can say that the SRH940s are much much closer to the HD800s than their prices would suggest.
Pros: Detail. Accuracy. very bright (if you like that)
Cons: Headband a little uncomfortable. very bright (if you don't like that)
Summary: I bought the SRH 940'S and by god there incredible headphones. The quality from the headphones is not at all like your really there, its more like you enter a whole different world when putting them on. The best way to describe it, is you are truly listening to the purest of audio. The 5hz-30khz response is no lie. Yes it seems a bit excessive, but you get exactly what you pay for. Ive compared these to the SRH840's, and the Sony 7506's.
Summary: Very comfortable, but a bit on the heavy side. Sound quality on good recordings very good. Running an amp makes a big difference. These headphones sure show how lousy most mp3 recordings are.. No regrets here.