When I was playing around with my Somic MH463, I noticed that in the pics posted by Boris there were vents around the driver on the side facing the ear:
(above and below the driver)
If such vents were not present, the driver should make an airtight seal with the ear (to the extent that the earpads seal the ear), making it possible to reproduce subbass down to DC frequencies.
I tried sealing the vents with tape and it boosted the subbass substantially (as heard playing sine tones with one side taped and the other not; unfortunately I did not take notes as to exactly how many dB louder that side got at x Hz).
I am especially curious as to how such a mod would work out with the Audio Technica AD series...:
with a big 53mm driver *surrounded* by even bigger vents on all sides, leaking all the bass away and making for a rather bass lean sound, by all accounts.
...because I'm interested in acquiring an AD500 for the reputation the ATs have for comfort, but I do like my bass
If you want to try this mod, just remove the earpads to expose the driver assembly and put some tape over all the vents around the driver. (duh?)
Interested in hearing your results! The best way to quantify the change in sound would be to do the mod on one earcup first and play some bass frequency sine tones before and after modding one side to check the level difference between the two cups (before and after, because the channels may be imbalanced to begin with).
On the other hand, are there any other recommendations for comfortable circumaural open cans with big deep cups (coz I have big ears and wear glasses) that are bassy? And a bargain price is always welcome