I have both but I like the 200 because it has less bass and better clarity than the 100. As a matter of fact,I modded my 200 with plasticine clay around the drivers for tighter bass and a different cable,a Griffin Survivor cable to be exact. The stock cables are not useful me so I switched to a straight cable. I amp my 200's with a Fiio E11 so I get plenty of volume.
But how is that? I feel the same about the Pro DJ 100 and 200. They should be the same. I'm still in contact with Koss and they said they should sound the same, but the support guy wants to talk with engineers and get back to me.
I now have the Shure 840 Pads on the DJ 100, which improves detail and clarity A LOT, but takes away the bass, almost too much.
And I have the Pro DJ 100 Pads on the DJ 200. I've been listening to the 100 exclusively since my last post, deliberately. And right now, as I type, I'm listening to the DJ 200 with the DJ 100 pads on a Fiio E11 attached to my little Retina 13" MacBook – sadly no USB DAC for me yet ;)
Bass seems to have improved a lot, compared to my experience with the stock 200 pads.
How can that be? They look exactly the same. Or I'm just too stupid. I'll take them off later and compare them again and do some pad-switcheroo and then post again.
Right know I can say that I kinda like the setup I now seem to have: Pro DJ 200 with 100 pads, improves bass and better clarity than stock Pro DJ 100.
Stock Pro DJ 100 -> too much bass and not enough clarity. Now with Shure 840 Pads just barely enough bass, super comfy and lots of clarity. Great mids and treble. A lot of detail. Almost Grado-like. Yes: closed Grados. ;) Well, not really, ;)
A duo of great headphones I now seem to be able to alternate between depending on mood ... ;)