Pensado breaks his low-end approach into three components: The Last Octave (40-80 Hz), "where most other engineers don't work;" the Next Almost True Octave (80-250 cycles), "where you really have to make the mix stand out on small speakers to give the impression of an enhanced low end;" and the Top End-and-a-Half (250-800 cycles)," where most engineers start muddying things up."
He also strongly urges us to never simply turn up the overall bass EQ to get more low end. The secret is in paying attention to which elements in a frequency range we're actually turning up.
"If we get too much 250 or too much 350, we're going to get that cardboard sort of muddy sound. I'll ask a student, 'Wait, what are you EQ-ing? If you want more bass just take the fader up.' Now, when you turn it up you've got some other frequencies you're interfering with, for instance in the vocals a bit. Just pull out a little 600 or 1k and the bass is still fat and round, and it sounds natural and life is good again. As you do that more and more, you'll acquire the skills of cutting and notching frequencies out of things instead of adding more. That's the difference between a major league engineer and a minor leaguer."