Summary

I present my attempt at a DIY headband for a pair of headphones, that can be made using just 3D printed parts and easily available materials.

The main structure of the headband is made from 3mm rod, cut to length.
This can be made from many materials, but I would recommend 303 Stainless Steel, Grade 5 Titanium or Carbon Fibre, as they are all suitably springy. This current design uses just under a metre of rod in total. If the band ends up flexing too much I might consider adding one or possibly two more rods to the middle span, to stiffen that area up have most of the flexing occur at the sides.

The printed plastic parts take almost no load when the headband is being worn, as the rods rest on each other. They just hold the rods in place using UNC 4-40 x 1/8" grub/set screws (M3x3mm screws would also work, but I prefer the courser thread of the imperial screws).

The headband is a slight remix of "GiraffeMetropolis' Audeze LCD Headphone Strap" and should be printed using TPU filament. It should be secured in place using either 4-40 or M3 socket head screws. ( a screwless attachment method may be a better option).
The Slideable adjuster tubes on the sides should be 5mm in diameter. More details on the assembly of these headphone arms can be found here: https://www.thingiverse.com/thing:5103331

There are two holes in the end blocks to allows tension on the slideable adjuster tubes to be added and adjusted, using a 4-40, M3 or 6-32 grub/set screw (very much a work in progress)

So far I've printed all the plastic parts, but I'm waiting for some titanium and carbon fibre rod to test it all with.