Help understanding 2nd order filter design.

First off, I'm I right in thinking you can control the slope (6/12ctave) of a passive filter (Hi-shelf in my case) with implementing a 2nd, 3rd order, etc filter?

Most of the detailed examples I could find on the internet seem to be for active designs...

Say for something like Dave's passive design, turning the low shelf(40hz) into a steeper slope. Is that something you can adjust with a 2nd order filter? Same thing with the Hi?

Here is my attempt at making a 2nd order HP.

C12 is fed directly from the input in the(signal generator) sim... the output is a 600 resister to common. I was following Dave's design to get -10db, but with the inductor in place it drops down to -30db?

I have the series resistance of L6 at 50 ohms... so I think I can see why it would drop down. Can I add a resister someplace to keep Dave's design at -10db?

I think the series resistance is the reason that it doesn't go all the way down to -infinity dB at dc...
Could you post the full circuit?

Edit: Disregard that first comment. There's a cap in series... Obviously there must be a parallel path..

Not trying to hide anything but... "C12 is fed directly from the input in the(signal generator) sim... the output is a 600 resister to common"

Also I'm talking about the slope of the shelf... as in hi-pass

Can you PM the .asc file so we can work on the sim?

It's just a signal generator, a voltage divider, a cap and a coil to ground. The output impedance is 600ohms...

I'm really just trying to understand how you change the slope of a passive shelf filter.