I believe I have spotted in error in many retailer listings of the Sennheiser HD 280. Many online retailers such as Amazon, HeadRoom, and Newegg all list the sensitivity as 102 dB. However this seemed very confusing to me, because the noise floor I was getting with them with my Schiit Asgard 2 would seem to indicate that they should be much more sensitive. Plus I was getting the same noise floor with my HD 380's, which retailers list as having a 110 dB sensitivity, and lower impedence.
So I checked the HD 280 manual, and low and behold, the sensitivity is listed as 113 dB. Right there in black and bold.
So anybody hoping to get the HD 280 for a dedicated amplifier beware, they are more sensitive than sometimes advertised, and you may suffer from an ostensible noise floor!
They're great for an ipod though, if you don't mind the clamp. I am planning on contacting at the very least HeadRoom about this discrepancy.