The *SpHEAR Project
The TinySpHEAR microphone is a traditional 4 capsule tetrahedral first order Ambisonics microphone. The picture shows the full design as previewed in OpenSCAD and a picture of the first prototype (built with Primo EM182 10mm capsules, 9.6mm microphone radius).
The four capsule holders come in two flavors, one for the upper two capsules and another for the bottom two capsules that connect into the microphone mount. The capsule holders have legs with fingers that interlock and hold the structure together. There are two styles of usable interconnections, horizontal legs (easier to print and assemble, a bit bigger) and vertical legs (more difficult to print and assemble but more compact).
Horizontal legs, 10mm capsule, 10mm microphone radius:
Vertical legs, 10mm capsule, 10.6mm microphone radius:
There is a third style of legs intended to print the whole microphone structure in one go in a more sophisticated 3D printer, but this has not been tested.
A couple of configuration variables in the source file can be used to switch to a "print" rendering where the individual parts of the structure are laid flat on the printing surface.