This instrument is a “harpobass”. The vibrating mode is the same as on harps: the strings pull the bridge and the soundboard, unlike a regular bass or even a double bass. The length scale is 860 mm (like acoustic or electro bass): therefore you can use bass strings. It can be played with a bow. It’s possible to put frets on the neck. The mic is an electrodynamic Schertler (with a XLR output). The woods that are used are: olive ash wood for the back and the sides, the soundboard is made of spruce (the sound post is adjustable below the high pitch strings), the neck is made of maple, the bridge and the tailpiece are made of ebony, the fingerboard is made of rowan. There are 4 BH tuning machines. 1 cello pic and a carrying bag.
The acoustic sound of the harpobass is very full and very powerful (2 or 3 times more than any acoustic bass). I’m the only instrument-maker of this bass model, it is the result of my research, I’ve worked hard on it for 4 years. It is lifetime guaranteed (my lifetime!)

You can see the latest model below.

And also below, you can see a few “curiosities” (kind of  “oddities”), the very first prototype of that kind…