I am deciding between the Senheiser HD-202 (closed) and HD-457 (open). The are very similar in all aspects. I will be using them to power a pcdp. I want as much volume as possible. should I go with the closed or open model?
Impedance: You need this figure to be between 16 and 80 ohms ideally... any higher than that, and you'll start to notice things getting quieter...
Sensitivity: the higher the figure the better... for todays modern, underpowered PCDPs, you want a figure of no lower than 100db in my opinion
Closed 'phones do give you a minor advantage by eliminating some outside sound... but, technically speaking (although this is by no means always the case) closed 'phones can sound compressed (no soundstage) and also can sound boomy (the bass bouncing off of the housings)