Strain Relief wire splice

Print it in the orientation it was downloaded in. No supports. Solder your wires together and isolate them by taping each down with kapton tape. Fill with epoxy or hot glue or something when done.

This is for 3mm aux cords and 4mm aux cords but it shouldn't be too hard to edit the freecad file for different sizes. It'll scale with changes to the profile sketches.