From the ML brainiac that we go to with questions -
"The passive radiators in our hybrid (Abyss) system are tuned to deliver significantly more output in the lower octave of bass, typically around 40hz - below. This gives them a big advantage over the single driver front-firing Dynamos when it comes to max output capability in the deepest bass frequencies. While the lowest bass extension frequency is almost identical in the specs to the Dynamo "price" equivalent, the Abyss subs will have a lot more headroom in that bottom octave."
Dynamo has an advantage in headroom in the mid-bass region (50-60hz)... "Dynamo 12 has a slight midbass advantage due to that beautiful single 12" woofer, but the Abyss 10 will leave it in the dust when it comes to 40hz-below output headroom."