Wow, these aren't ksc-75's anymore!  I was expecting just some damping changes or kramer type drilling. 

So you left the driver in it's stock plastic housing, inside the grado cup?

Ohhh.....I want to listen to these!!!

LFF, you are very welcome to have purrin send them to you. It would be very interesting to read your impressions and have you try some of your damping skills on them. They are very easy to work on, since the drivers can easily be popped in and out, there are no screws etc.

FYI, I have made the differences visible.  And I am sure damping the interior and/or completely sealing the cups can flatten out the bass response from 100 - 250hz further. It's kind of hard when you can't check the effect of changes without having access to measuring equipment. Because changes will certainly effect the mids and higher frequencies too. And when there is something I especially like about the Stratos then it is the mids and the, to my ears, nice balance.
I am working with SinGen and trying to even out the response.  What sending the StratoKOSSters in for measurement did was helping me see that in fact you can plot your own curve when working with tools like SinGen. Actually I learned that I can trust my ears, because the measurements mainly correlated to what I was hearing when using SinGen.
On the whole, I think the closed KOSS are little gems, for all their cheapness and flimsy looks. I would be more than happy if people tried the mod out themselves. I think it is a rewarding experience.

Pads do play an important part in the mod.

Purrin said he would try out damping variations and I am looking forward to reading about any changes that he comes up with.

As I said, I do think there is much you can do to play around with the response (playing around with damping and cup volume, sealing or opening up the cups with some kind of bass venting ...). The problem is, it does not help (especially in this forum) if I do it and say now the curve should be dead flat or something, when there is no  measurement or objective data ;-) to make people see what I am hearing.

As a matter of fact, at the moment it is just me and purrin, who both see the graph and know how the headphones (this specific prototype, with this wood, cup diameter, cup depth, damping scheme and leather pads) sound. I guess at the moment only purrin can comment what he believes (from listening to the headphones) contributes to the dips around 200hz and 4k and if they are sonically malign or not. I do not have enough knowledge of interpreting graphs and plots to comment and speculate on those issues.

The StratoKOSSters I sent in are a prototype, I was not really dead careful assembling them, didn't bother to recable them etc. I just wanted to see the measurements to find out if I was on the right track with what I was trying to achieve and show others how dramatic a change it would be to put the KOSS into cups like the ones I used. I have been trying to mod Grados and Symphones Magnums, but doing those I have never come up with changes as huge as with this mod. And to my ears the modded phones sound better than stock. But then again, that may very well be just me. And I know that others might quite probably disagree.

No prob, I am in no hurry.

The dip from 100 to 300hz kind of reminds me of the Beyer T70 dip. I was thinking that it may well be that it is not really harmful, since it does not bring the system out of balance and might give the sonic impression that the bass extension is even better without an overwhelming mid-bass hump that dominates the bass response.

Anyway, it should be possible to deal with it. As a matter of fact, I have a low profile cup version and a PS1000 clone version as well. Neither of those has this dip, could very well be that I was a little sloppy with the damping. In my other systems I have the cups lined with acoustic foam and I am using a damping "sandwich" of a thin disc of open cell foam, fibrefill in between and another disc of open cell foam facing the back of the driver.

I am curious as to what you will find out.