This is one of my first designs so I may come back in the future to make it work better with a standard printer.
To fit most standard headphone sizes you will need to print it larger than a standard 200x200mm bed size. Try printing in parts and scale it up so that the full stand would take a 300x300mm bed to print.
INSTRUCTIONS: There are three options.
1 - Folding Headphones: Print it in one piece to fit your bed - which may not be large enough for standard headphones. This is based on a 200x200mm print bed. Scaling to a 300x300mm print bed may be large enough to fit standard headphone sizes.
2 - Print Headphone_Stand-Tall.stl which should be tall enough for your headphones. This may be taller than your printer build area, so it is obviously dependent on your printer.
3 - Non-Folding Headphones: Print the 4 parts separately then glue together. The 4 separate parts are scaled larger to be big enough to fit standard headphones when assembled.
You may have to scale the file down to fit your print bed.
Orient the face you want to print on - Cura flatten to bed is located in the rotation menu. Simplify 3D flatten to bed is located in the edit menu (ctrl-L or apple-L). Other slicers... I don't know.
There are two main faces to print from. The easiest would be the back face. If you have amazing bridging capabilities on your printer then you can print it on the bottom face.
Print, use, enjoy!