Dan Clark Audio (formerly known as MrSpeakers) has kindly made public the files and instructions for creating his famed Alpha Dog / Alpha Prime planar magnetic headphones. The project uses the headband and drivers from a set of Fostex RP-series headphones, along with other parts and materials, to create true audiophile-level headphones:

https://www.head-fi.org/threads/open-alpha-t50-3d-printed-headphone-project-from-mrspeakers.825868/

These are files I have created or modified based on those provided from Dan Clark (MrSpeakers). Any attribution should include him. https://www.danclarkaudio.com/

All of the ear cup files here include reinforced screw hole bosses to make them less likely to twist off when printed with filament printers.

There are three different versions of the ear cups:

1) The original files (which use a hirose connector) with reinforcement added.

2) A modified design (which uses a 2.5mm mono TR jack) also reinforced.

3) A modified design (which replaces the bass vent holes with an adjustment screw) with hirose connectors and reinforced screw bosses.

For the baffles, the original plans called for the baffle plate and pad ring to be printed separately and glued together, I had success with merging these parts into one piece and printing it vertically with little or no support. This version also has a little more clearance around the driver mounting surface.

I have also included templates that can be printed to assist with cutting the ear cup gaskets and felt inserts.

If you would like to modify my modifications, you can find my source files on TinkerCAD:

Left Cup (2.5 mm jack, reinforced):
https://www.tinkercad.com/things/cJ1mDoeQ3Wt

Right Cup (2.5 mm jack, reinforced):
https://www.tinkercad.com/things/a9SVYG23nyC

Left Cup (Hirose jack, reinforced)
https://www.tinkercad.com/things/ac2ObwHCaCz

Right Cup (Hirose jack, reinforced)
https://www.tinkercad.com/things/bFkIVDMiapl

Left Cup (Hirose, bass adjustment screw, reinforced)
https://www.tinkercad.com/things/ktqwlRUPsY5

Right Cup (Hirose, bass adjustment screw, reinforced)
https://www.tinkercad.com/things/aRpowoEi5KQ

One-piece Baffle
https://www.tinkercad.com/things/aB857ReKDy8

Ear side felt cutting template
https://www.tinkercad.com/things/67PFtjAkzmN

Cup gasket cutting template
https://www.tinkercad.com/things/0oTNXVKIY0O