The first run of 325 cups were black anodized aluminum. Grado then switched to the silver cups.
These pre-dated the RS1/2 and were John Grado's first attempt at a premium/professional headphone.
At the time he was trying to "replace" the HP1000 headphones which were no longer being made.
He basically increased the size of the outer cups (to match the HP1/2/3) and made them of metal instead of plastic and then selected the best possible drivers.
The drivers were either lower matching HP1000 or the pink transitional drivers.
When John developed the RS1/2 he made the RS2 cups the same size as the 325 ie. larger than the plastic SR but smaller than the RS1.
Seems he thinks size matters....
Edited by parbaked - 6/26/13 at 5:20pm