HE-500 Closed-Back Mod

I've posted this in a few places, hoping for some input from some more experienced modders.

I'm experimenting wtih a closed-back mod for the HE-500, just to see if I could increase isolation, emphasize bass, and otherwise customize the sound.




I'm using 3D printing to iterate on this.
Positives so far is that they're light, rigid, non-destructive, held in by friction alone, and easy enough to install/swap that you can do it while you're wearing them.
Negatives is that bass response is poor and treble is very harsh.

I'm experimenting by tweaking the cup shape and adding some dampening material. My current iterations have gone from shallow (>15mm) & flat ---> the current version, which is 30mm deep and hemispherical concave with 3 small bass ports. These versions seemed to help somewhat, but not solved the problems. Unfortunately I have no way to measure these, so I can't tell what the incremental changes are making, and whether I'm going in the right direction.

Any thoughts/suggestions are welcome!

Some pics:

Previous versions
http://i.imgur.com/9S1CXsS.jpg
http://i.imgur.com/siHB636.jpg

Current version
http://i.imgur.com/7UxQdJa.jpg
http://imgur.com/a/KzrhR

 

From my modding closing off the backs of my HE-6 killed bass made a valley around 500Hz and pushed 3-10kHz WAY up with a peak around 7kHz. It was pretty bad. If you are going to make closed cups you'll probably need to experiment with front damping materials as well. Definitely try some acoustic fiber in the back to minimize reflections.

 

You'll need a whole lot more damping than that for a bipolar driver.

 

I agree, this driver will need more of everything in the rear.

It is my guess,

That you would need to almost double the cavity of the cups, making them deeper, and make them angled & ported if you want the driver to "see" even more open space.

Then the driver will need to see some front ear side felt damping all around with less in middle.
This is only my educated guess.