En este hilo explican como hacer un filtro paso alto por debajo de 20 Hz
en una etapa NU.......DSP
How to extend the high pass filter below 20hz in DCX2496 - AVS Forum | Home Theater Discussions And Reviews

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.

Saludos.