Philjolet,
I would say that there is a real size differential in the sub diameter, versus the midrange diameters, therefore a possible speed issue...however.
That, and they cross over at 60 Hz as I recall.
Was it a perfect blend, NO, but in my opinion, outboard subs are never as seemless as single unit loudspeakers.
With very careful movement, (parts of an inch) back and forth, one can time/phase the speakers into a very seemless sound.
Not everyone can do it at first, but if one carefully listens, experiments and is dilligent, the work will be worth the effort.
Johnathan Valin, who is a dillitante of the first order, had a love affair with the Pipedreams some years ago. I'm forgetting the actual text quotes, but it was as real as Sandra Bullock and Jesse James, and lasted longer, I'm thinking.
If you trust his ears, (I do some times) read the review and use it as a guide.
These speakers, when set up carefully, correctly, can be magic.
good listening,
Larry