Various luthiers around the world have been trying for years to find solutions for building »less bulky« double basses without giving up any bit of its characteristic sound. Although the size issue seemed to have been overcome with the first electric upright basses, sound continued to be a problem. An EUB often sounds like a fretless bass, but nothing like a double bass.
Through my own research, I have come to the following solution: The sound box is built using the same criteria as those for a traditional double bass, but smaller in size. Since a smaller sound box does not allow the instrument to produce a strong acoustic sound, once the sound is amplified, its quality matches that of a double bass, even when played with a bow.
I play the double-bass myself, in addition to being a luthier, and therefore I find it easier to have the instrument amplified without incurring resonance problems. Look at media to listen to the sound demo