My guide to EQing all my headphones to my ideal frequency response starts here:
It takes a lot of steps and I don't have the energy right now to write a complete guide so I'll try to walk you through step by step. First you need to install Virtual Audio Cable and VSTHost on your computer
And get it working as per this review http://www.head-fi.org/products/beyerdynamic-dt-770-pro-closed-studio-headphones-250-ohms/reviews/5928 (but replace SAVIHost with VSTHost) so that you can equalize system sounds using VST plugins. And instead of his Marvel GEQ you need a parametric EQ like Electri-Q
which is what I use. The paid version may be less bugg though:
(I know how to work around the bugs in the free version but it may be easier to work with the paid version)
Come back to me when you've got this setup working so you can hear system sounds (such as stuff playing on youtube or spotify) being changed when you play with Electri-Q in VSTHost, or if you have problems setting this up and we'll discuss what to do from there.