http://www.brentbutterworth.com/headphone-voicing.html
Here's an article on baffle modding i think you'll find useful
this was his results:
1) Changes made in front of the driver, between the driver and your ear, have a much larger effect than changes made behind the driver. (This also makes me wonder about the efficacy of using exotic materials for driver enclosures.)
2) Changes to enclosure volume and stuffing have minor effects, while changes to rear porting have greater but still relatively subtle effects.
3) Opening some of the dampers on the back of the driver can provide a useful midrange boost.
4) Adding ports on the front baffle is a precise way to make major changes in the bass response.
5) Adding soft or semi-hard damping material in front of the driver reduced both low- and high-frequency response, without affecting midrange or lower treble.
6) Adding solid material to block part of the driver is a precise way to make minor adjustments in the bass response without affecting treble.