By now you know my thoughts on the Obligato Pirastro, but since I'm just testing them for the next concert, I noticed other qualities of these strings.
Often times the fourth string is the weakest, while the Obligate SOLO is the F # that provides great satisfaction from a sonorous point of view. In this case the whole set is very well balanced. The sound is more characteristic of this sound like the casing that has a loss. The reactivity of the string under the bow is of some significance and frequency of vibration allow you to can play in any position without major problems.
My students are starting with the Obligato all, when then they want to change to a thin string (now go to the very fashionable iper-thin strings), and more manageable, which will shorten the strings steel or aluminum are more easier to be played under the hand left, but the sound is no longer in the gut to which they were accustomed and do not know what to do. The hyper-thin strings are going good for exhibitionist but not for a bass player who wants to hear the stamp of the past three centuries (and perhaps more).
Today we hear many "contra-cellos ', a kind of instrument that no one knows where to place, why not a double bass and is not a cello. The Obligato (Orchestra or Orchestra) for me to remain the only clearly define the timbre of the double bass. On this I have no doubt. Whit Obligato you will have the sound of three/four centuries ago.

Vito Liuzzi