Miniature portable Bluetooth stereo audio exciter

This is a very small device that can be used to play audio from any Bluetooth enabled device (ex. Smartphone, tablet, watch, etc.) by simply placing it on a cardboard package or any other surface that can vibrate freely.
Can be built very easily, using just a few components. The whole case is 3d printed.
The final products look like in the following picture. The full size (L x l x h without the exciters cap) is 76mm x 38mm x 36mm or 3” x 1.5” x 1.5”.

A short video demo:
https://www.youtube