Sennheiser HD 700s need a lot of break-in?

Just received a pair of HD 700s today and I am pretty disappointed by the sound. It's very dull and closed sounding. Not what I expected. My 10 year old HD 600s sound far better right now. Those do have the Cardas cable but that can't be the sole reason. Does anyone have any experience with the HD 700s? Maybe they need a lot of break-in time? Any help is greatly appreciated!