I am wondering if there is a noticeable performance difference between installing the contact mic unshielded as instructed in a can vs making the universal shielded contact mic and then temporarily taping it in a can? Also, is it worth the extra effort to use plasti dip coating instead of electrical tape? I’m going for the thinnest most sensitive shielding process.
Plasti dip on the outside is strictly optional. It looks neater, and helps hold the copper tape together longer, but is otherwise non essential. Our tests show no measurable difference in sensitivity, but theoretically it costs you something. Inside the mic, between the piezo and the copper tape, it is essential to insulate the disc from the tape. Plasti dip has proven very unreliable for this purpose, so we only recommend a layer of electrical tape.
As for the tin can mic question: Please look at our silly videos promoting the Hula Mic gimmick. This project involved clamping or sticking a complete, shielded mic to all sorts of trash. It is still quite sensitive. The object itself is a much bigger factor in how the mic sounds than the layer of tape on the mic.
In all cases, the sound is heavily influenced by how well the mic is coupled to the vibrating object. Whenever possible, use a little spring clamp and a pad to hold the mic down firmly to the edge of your object. When that’s not possible, we like to use a very small bit of poster tack, mushed up warm and soft, squeezed into a thin sheet, to stick the sensor to the middle of the vibrating object.