I was at the local flea market recently and happened upon a vendor selling vintage headphones for $5 and ended up picking up three pairs on a whim. My original intention was to adapt them to work with modern systems, but I soon found out that, after nearly 100 years, the magnets were no longer magnetic, and so I figured I would completely retrofit them with modern audio. Now the problem I ran into is that most, if not all full size modern headsets use speakers that are too large for the housing on an old pair of Brandes headphones. I then considered ear buds, and found that they do work, just not very well, so I tracked down a pair of wrap around the ear type phones, at the local dollar store, which seemed to fit the criteria for what I needed, and adding the fact that they were cheap enough that, should I damage them in my experimentation, it wouldn't be any big loss.
The dollar store headphones seemed to work better than expected and provided much higher quality sound than I could hope for, but I wanted to make the headset modular, so that should I opt to change the speakers in the future, I wouldn't need to go through an entire assembly process. Suffice it to say, my soldering skills aren't the greatest and attempting to reattach the delicate wires on a headset is less than appealing.
Another aspect I wanted to improve was comfort. With the ear pads made out of bakelite (a pre-war plastic) they could be a bit rough to wear, so I performed a bit of research and found that there were versions that used a leather cover as a padding. So, I attempted to design my own.