Etched Fabric Speaker
Similar to the paper speakers these copper fabric speakers are created by etching the copper off the fabric in order to create a coil. If you then run a 5-9V amplified sound signal through this coil and hold a magnet close to the center of the coil then it will make sound. Unlike most speakers that have the wire coil wrapped cylindrically and placed around the magnet, here the coil is in the plane and directly part of the membrane that moves the air creating sound.
For more details please see the paper speaker post:
Using masking tape to mask both sides of the areas you want to etch away. Then apply Vaseline to the exposed areas (both sides!).
Carefully peel away the masking tape, without smearing the Vaseline everywhere.
Submerge in a bath of salt (1 tablespoon) and distilled vinegar (1 cup), proportions are rough. Let sit for anywhere between 4 and 12 hours. As the copper dissolves in the acid it creates
When the copper has etched away, rinse thoroughly and then iron between two paper towels to remove remaining Vaseline.
Other fabric/thread versions
on canvas (good), stainless steel thread on canvas (okay)
Stainless steel thread between masking tape (okay), stitched to paper (bad)