TB Bamboo!

 Interesting looking cone! Lots scrunched up in there.

.22 cubic foot or just under 7 liter box. Port 2" x 5" long. Box lightly stuffed with wool. Piezo on back connected to .33 uf capacitor + 20 ohm resistor across. Everything sounds right. Bass is tuneful and treble has typical piezo fizz but I enjoy the liveliness of piezo's! This driver sounds extended but needs a tweeter (pick your poison) to provide more realistic treble. Small rooms don't require sub but larger rooms do.

4" Bamboo next to 3" aluminum TB. They actually sound very similar.