OK, where my sealed guys at?
If you set a 20Hz high shelf filter at 6dB/octave to -2.5dB, you can make the response of the nuke flat to 10Hz:
Green: Amp response with no EQ into 4 ohm load -starts rolling off at 42Hz, 1dB down @15.7Hz, 3dB down @6.6Hz
White: Low end extender curve into same load -starts rolling off at 9.6Hz, 1dB down @6.1Hz, 3dB down @3.2Hz
For those of you sealed guys with a more advanced skill set who have measured the rolloff of their signal chain with loopbacks in REW and need to compensate for the cumulative rolloff of your components or of just your AVR's sub output, I came up with a few options to bring back up the ULF:
Yellow: Flat amp response
Purple: 20Hz, 6dB/octave high shelf at -4dB
Red: 20Hz, 6dB/octave high shelf at -6dB
Teal: 20Hz, 6dB/octave high shelf at -10dB
Grey: 20Hz, 6dB/octave high shelf at -12dB
Green: 20Hz, 12dB/octave high shelf at -10dB
For the above rolloff boosters, I'd recommend testing with worst case scenario content (ULF) and ease up the level while monitoring excursion just to make sure you're not going to put yourself in a dangerous situation with your drivers. As with the HPF cheats, the low shelf attenuation will raise the noise floor and you will have to re-calibrate your sub level. I recommend doing that by using the front knobs on the amp (or worst case the gain in the DSP) as opposed to maxing out your AVR trim as this has shown problems with clipping strong re-directed bass signals in all of the AVR's that I've tested.