In response to my e-mail, Pirastro tells me that the string tensions of Obligato and Original Flexocor are:

Obligato 120,2kp
Org. Flexocor 125,0kp

Can somebody make sense of this? For example, Spirocore tensions are listed as 30kp to 33kp.

Francois, you were saying..............

It seems to be the sum of the four strings tensions.
From my work with Pirastro strings, it seems they usually design their strings with the most tension on the G, then falling down to the E, which has the less tension. I'd say (this is my opinion, not a proven fact)that this is true with Chromcors , Permanents and Flexocors, but may be different with Obligatos (I only tried the G) and Original Flexocors.
In the Original Flex, the D seems to have much less tension than with the Flexocor '92.
On the other hand, the Original Flex A and E are much thicker and higher tension than Flexocor '92.

If you make the sum of medium 3/4 Spiros tension, you get 126.5kp
If you make the sum of weich 3/4 Spiros tension, you get 114.5kp

The Pirastros seem to be in the same range, but the tension distribution in the set is probably quite different. (Thomastiks have higher tension on the E, decreasing toward the G)

Hope this helps!

I knew that.

Seriously, nice job, Francois.
That certainly explains why my Obligato seems so flabby when bowed.
Reducing tension going from G to E is the opposite of what I would expect. They must have their own rationale; I would like to hear it.

Don:

"Flabby when bowed" is a very accurate description of the Obligatos. I am certainly less pleased with the strings now, then when I first placed them on the instrument.

I have had this same discussion with Old Saw, and I know he concurs.