Although the sennheiser HD650 are a fantastic sounding headphone, they do leak a lot of sound (which can be harmful during a recording) and they do not isolate (something I dont like while I use these for drumming).
In order to make these headphones more isolating and less leaking, I will try to close the back end.
I will use a sound absorbing product, attach hooks with elastic to the sound isolating product, and hook it around the earcup.
I hope there is a sound absorbing product that is capable of the job, so that most leakage is literaly absorbed.
In order to make them more sound isolating, some kind of sound reflecting product like hard plastic could do the job.
So basically what I want are two sound absorbing and sound reflecting patches that I can hook around the earcup.
Since this will probably effect the sound quality a bit I want it to be an adapter, so that it can be removed without damage to the hp.
I think this will help in the sound leakage department, unfortunately in order to make it a sound isolating headphone it will need specialised ear cushions, something I dont know where to get or how to make.
I think this could be a cool project.