This instrument is a harpobass. The vibrating mode is that of harps: the strings pull the bridge and the soundboard, the opposite of a normal bass or even a double bass.
The vibrating length is 86 cm (like acoustic or electronic basses): bass strings can therefore be used. Playable with bow. Possibility of neck fretting. Microphone: Schertler electrodynamic (XLR output).
Woods used: back and sides in ash and olive, top in spruce (adjustable core under the treble), neck in maple, bridge and tailpiece in ebony, fingerboard in mountain ash. 4 BH tuners. 1 cello pick. 1 carrying case.
The acoustic sound of the harpobass is very mellow and powerful (2 or 3 times more than any acoustic bass). I am the only manufacturer of this type of bass, the result of 4 years of work. Lifetime warranty (mine that is!)

Below the latest model.


And here below, some oddities, first of a kind prototypes…