I've been putting together some planar magnetic loud speaker drivers. There is a wealth of information available at diyaudio.com, particularly in this thread. Inner Fidelity have a nice write up on planar magnetic drivers. Euwemax documents his DIY planar magnetic drivers for headphones, and he uses etching as his principle method. I thought I'd attempt to build some using enamelled wire and embroidery hoops. This post documents my progress so far. I've made working prototypes, but at the moment the sound is clipping.