Sennheiser HD800 headphones Measurements
As Keith Howard wrote in the August 2008 issue, deciding what, exactly, is the optimal frequency response for a pair of headphones is neither obvious nor trivial. The only measurement I perform on headphones, therefore, is of their electrical impedance, to determine how difficult they are to drive.
The result for the Sennheiser HD800 is shown in fig.1. (I wore the headphones for this measurement.) The impedance ranges between 340 and 650 ohms, which is considerably higher than the impedance of Grados and Sonys. The HD800 will therefore be very easy to drive. While it is unlikely that someone will use the bulky Sennheiser HD800 with an iPod, the specified sensitivity of 102dB/V should mean that the headphones ought to play loudly enough for all but the most fanatical headbanger.John Atkinson
Fig.1 Sennheiser HD800, electrical impedance (solid) and phase (dashed). (50 ohms/vertical div.)