Thanks Earl, I was pretty sure of that. I purchased the Symbiotic diaphragms from a member here after being told they were the same motor. And yes, I call them bowling balls. 30Lbs is about right.
I just wanted to bring this up in this post as often the 291 drivers can be found a lot cheaper. I always just assume when buying used drivers that the diaphragms will need replacing anyway. I picked these up about 3 years or so ago for $100.00 for the set. Another $100.00 for the used diaphragms and I was set.

BillWojo