Thanks Jeff!
Yeah bass that low is a tricky one. We're only in F#, our bassist just bought a fan-fretted Dingwall so with a huge scale and massive cable-esque strings it can go that low with reasonable intonation. We haven't recorded it yet though, the bass on this is Trilian and is matching the low notes an octave below as well.
The lowend here actually has a lot going on to get decently tight; your typical sine-y synth blended in for the sub stuff, as well as lots of extra harmonics generated and pumped into stages of compression / multi-band to control it.