Here's a file showing the frequency response of two filter types. The top is a cascaded 2 pole filter and the bottom is the libraries shelving filter. If you switch between lp and hp it's pretty obvious the slope is starting way to early. I'm assuming the Fc should be down about 3 or so db, but his looks way off. Am I doing somethings wrong?
Note the bottom trace shows Fc. The first slope is a normal shelving control, the second factory slope is the curve at Fc.