Okay , I just realised why my answer seemed so odd.
For some reason I completely missed the [b]3[/i] spool bit, instead reading it as single spool.
Imagine that I've said something profound about the extra stiffness and weight of a triple spool compared to a two spool engine, and skillfully compared then both as the sizes of the engines grow from about 50,000lbs thrust to 100,000lbs+.
I'll just shut-up right about now ..... Grrrr ....