Here is how it works illustrated in WinISD (divide the frequency scale by 10).

The green line is the target curve--a 2nd order high pass filter at 10hz.

Step 1: The red line is a 2nd order high pass filter at 20hz. Enter this in the DCX.

Step 2: The yellow line is a 12db/octave high shelf filter with negative gain of -12db also at 20hz. Enter this in the DCX.

Step 3: You're done. When these two filters are combined, they produce the target curve.

If you need a different high pass point, just adjust how many db of gain are in the shelf filter. For example, a setting of -6db should provide a high pass filter at around 14hz.

Step 1 detail.

Step 2 detail.

Update:

Many have asked how to set this up in the iNuke DSP. The filters are the same.

Here is an example of how to set the filters for a i would suggest a 2nd order 16hz high pass filter.

iNuke can't set filters below 20hz, but that is no problem. We just start with one at 20hz, then add a little shelf to push it down to 16hz.

Here is exactly what to put into the iNuke DSP.

Step 1: On the FILTER tab, enter 2nd order High-pass filter at 20hz (Butterworth, 12db / octave)

Step 2: On the PARAMETRIC EQ tab, enter Filter 1, Gain -4db, Frequency 20hz, type: HS12

Then use filters 2, 3, 4, etc. for any other EQ that you wish to add (e.g., to help correct for room modes).

To set their filter lower than 16hz, just add more "negative gain" in step 2. If adding a total of -12db negative gain, the 20hz high pass will be pushed all the way down to 10hz.