Sorry, I can't write a detailed guide this time... because there is too much to be done. But essentially...
Felt on the plastic rim/lip surrounding the driver. Then shelf-liner material in the slot left by the angle. This shelf-liner will absorb some excess resonance in order to reduce the midrange harshness that I mentioned (2-4KHz), I have used this technique with a similar headphone with good results.
Next: circular foam piece covering the edges of the metallic part in the back of the driver. This absorbs reflections that mess with the mids, too. Then another piece of shelf-liner in the lip here, too.
And here's the cup: treated to shelf-liner with bigger openings and dots. The bigger dots absorb reflection better than the smaller ones, so this one will allow for higher frequencies to come out better as they don't get reflected and cause destructive interference with the wave coming to the front. Edit: not visible from photos: dynamat under each piece of shelf-liner on the cups to dampen every possible resonance of the cup from lower frequencies. So essentially, I wanted to make the cup disappear...
And here are frequency response measurements before and after... I used my iPhone's microphone to record a sine wave sweep, so please ignore bass below 125Hz. iPhone mic sucks at recording bass. But midrange and especially treble showed some improvements.
16KHz peak gives more air IMO. The Sony R10 also had that peak from one measurement I have seen.
Edited by cdsa35000 - 1/9/15 at 3:14pm