One thing to note is that I was able to get a much better seal for these measurements, hence lower bass distortion and lack of bump at 50Hz as with the prior measurements. This is really not too different from what we've seen with the HE-400 Jerg Pad measurements where if we allow the open vent, we get a FR bump around 50Hz, but with increased distortion below that.
This correlates with my initial subjective experiences of the Abyss at THE SHOW, where I felt one unit's sub/low bass quality was not as good as the other one. It would seem likely that this is attributable to seal and recording used (low bass drops). Most folks who have heard the Abyss feel it's got quite a punch or bump around 50Hz. This is actually a result of a less than perfect seal. Now there is absolutely nothing wrong with this sound at all, but "leak mode" for a lack of better term, does result in more bass distortion below 50Hz.
I bent the headband inward more and messed with the pads a bit to made sure the lower back of the ear did not have any gaps. This changed the bass quality a bit. Less of that punch - more neutral - and much better quality sub/low bass (not that this really matters because most of the recordings I listen to don't have much energy in that region). Again, one can see this as a feature and adjust things accordingly to taste - not too much different with the Jerg Pads on the HE-400.