So, it looks like Pioneer?/Andrew? is nixing the SP-BS4X bookshelf which had a 5-1/4" woofer, while keeping the SP-BS2X with the 4" woofer.
I wonder if it didn't sell well or if they recognized a difficulty in using the 5-1/4 woofer for bass and midrange at the same time?
The SP-FS52 drivers are designated as 1ea 5-1/4 midrange and 2ea 5-1/4 woofers (and 1" tweeter). 3KHz and 250Hz are the crossover points. It is unclear (to me, anyway) whether the midrange driver plays below 250Hz or not.
Go to the "Manual & Brochures" link for specifics. The main page just lists 3 5-1/4" woofers
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Home Theater Speakers | Pioneer Electronics USA
At $200 for the pair from TD, I had to check them out. FS52's on order
(Thanks to ADTG for being the standard bearer and proof that I don't have a
real problem!)