yrs2012
I think what witzendoz is saying (and the diagram) he linked shows is..that, 1-D-sub connector, can only support 8 balanced jacks, with the 13th pin not used.
So for your application, you would need two D-subs. One with 8 connectors, and 1 with 4. Curious, What does the 25 pin connect to?
Ron