how to make a nice membrane with perfect tension.
as a playback membrane i decide to go with bamboo and a sort of plastic diaphragm.
back in the days they used skin or thin leather similar to drum skin.
i use techniques from condensator mircophone building. this one i learned from an old man who built his own condensator capsules back in the 50ies.
the trick is to glue the diaphragm to a heavy ring.normally aluminum (i used a tape roll which was heavy enough). then put glue to the bamboo piece and lay the ring with diaphragm on top. the weight of the ring gives perfect tension to the membrane. this is how high quality condenser microphones are still made. just use a metalized polyesterfoil (from a chip package or lila pause ..to fix your damaged microphone...sorry for that little excourse to microphone repair...)
so here some pictures how i made the diaphragm
the tape as weight ring and the plastic that serves as membran fixed with rubber :
my bamboo piece sanded down.
add glue to the bamboo
put the ring over the bamboo piece.
next day, when glue totally dry cut out the membrane.
perfectly tight and good tension.