Let's dissect this thing:
The left side will be exactly the same, so I'll only show you how to dissect the right side.
Step 1: pull the ear pad off. You can either start pulling at the rear or the front of the headphone. I usually go for the rear, but it doesn't matter.
Wiggle it a bit if it's being difficult. Either way, the ear pad should come sliding off. Like this:
And we have the exposed driver:
Apply dynamat (or similar material) on the inner lip like so:
And on the outer lip like this:
Alright. That's it for the outside.
Step 2: getting to the innards... unscrew the 4 screws in the spots I have highlighted:
And after that, BE CAREFUL NOT TO YANK OFF THE WIRES IN THE BACK!!
Grab the whole front enclosure (including the red ring bit) and gently lift it from the front... like so:
Once you lift it off, set it down gently as well. The wires are very very thin, and though I'm sure they won't come off that easily, please don't take any chances with them! It's a hassle having to solder wires that small.
Anyway, here you can see a bit of the other stuffs that I did: one piece of dynamat on the back of the plastic enclosure, and a square-ish sheet liner material on top.
Here's the other mod: dynamat pieces lining the enclosure close to the top, next to the bass port. Make sure you do this for both sides of the bass port.
Okay. And that's the inner enclosure. Let's get even further inside!
Step 3: getting even deeper. Unscrew the 2 screws at the spots highlighted.
The driver baffle should fall right off, but just to be sure, lift it from the front again (note: front means no wire). And here you can see a part of my mods again: piece of foam directly in the back of the driver. Any crafting foam about 2mm thick should do.
And here's the rest of the mods... in overview: dynamat circle directly on top of the plastic enclosure opposing the driver, then the same sheet liner material on top. Then more dynamat in the slot on top and one small piece of dynamat on the small square piece on the bottom.
That's not all. There's also dynamat on the top here. One piece on the extra plastic space beside the bass ports, and one piece directly blocking the square hole. You'll know what I mean by "square hole" once you open your headphone up.
the piece blocking the square hole needs to be the exact same dimensions for both sides. This is important, otherwise you'll have channel imbalance. The exact dimensions are up to you. Bigger square = more treble/clarity, less bass. Smaller square = retain some bass/warmth. You may also opt to not do this part.
On the other side: you already saw the foam piece sitting on top of the back of the driver, and also... dynamat pieces lining the plastic space between the 3 screw holes
Last but not least, push a piece of foam that's cut precisely to the bass port's size, and then shove it in there like so:
And... that's it! Enjoy!
If you would like to do more, go here for stage 2 of the mod.
Links to purchase stuffs:
Dynamat (you may get away with this much, but I'd suggest purchasing more to be sure):