iPhone amplifier with resonance box
The idea to amplify the sound with a resonance box is probably older than the guitar.
I saw this idea on the webpage of holzwerken.net and copied the box with wood of used wine boxes.
The effect of the box is astonishing. Especially the deep tones of the music are much better with the box. However, the box is not suitable to amplify the music for a bigger room or a hall.