2-pole active filter question

Hello! I am desiging in PSpice a 2-pole active filter. the values are taken from a wikipedia example to be sure about the fcut.

http://i1284.photobucket.com/albums/a578/fovos1/activefilter2polesallenkeytopology_zps30b85696.png

this is the circuit http://en.wikipedia.org/wiki/File:Sa...ss_Example.svg

and the fcut=16KHz. but when i am doing it in pspice the fcut is at 10khz.

i tried with other values and again problem. i read about FREQUENCY SCALING FACTOR accoring to Butterworth filter but i don't understand
why for example wiki has wrong fcut. what is this value?

at pages 9 to 10 texas instruments has some tables with FSF depending of what filter design you like.BUT ONLY ABOUT LOW PASS FILTERS....
http://www.ti.com/lit/an/sloa049b/sloa049b.pdf

please someone to explain.thanks a lot

 

Please chech here:http://en.wikipedia.org/wiki/Sallen–Key_topology

George