I got some inspiration from the Sony R10 headphone. The geometry is eyeballed and by no means has any since behind the tuning. I just need a cheap headphone for gaming, so I design the case to hold the cheap driver. The sound is quite interesting, as there is indeed some “room effect" with this ear cup and did inject a bit artificial sound stage to the recording that does not have any. 

You can reference the BoM for the additional parts you will need for this headphone. You might also want to get some tuning sheet if you'd like to play with the sound. 

For the headphone socket, I use 3.5mm TRS socket as it is the easiest to find the after market cable if you do not want to make your own. If you want to use the Denon pin out, then the positive driver pin need to be connected to the Tip and the negative goes to the Sleeve on both side. 

Update:

I have modified the design to make the mount fit more types of drivers. There is also tuning holes been to the ear cup to boost the bass performance.