So, that silver paper like material is not considered the diaphragm? I assumed the plastic material covering the voice coil and driver magnet was referred to as the membrane. If so, I stand corrected. It's much more than just simple cosmetic changes, the new material is much more resistant to changes in climate as in very cold to very hot and humid climates. The older black materials were prone to sagging after long exposure(months) to such conditions.
Sennheiser has not officially confirmed a change was made sonically, but many(through AB testing) have confirmed that the updated HD580/600/650 do in fact sound brighter than the older versions. The change was reported made sometime around 2006. At the time the HD580 was still in production.
Edited by Digital-Pride - 8/3/11 at 2:59am