These drivers all look good -
- RCF MB12N301 & MB12N351
- B&C 12NDL76
- FaitalPro 12FH500 & 520
- Eighteen Sound 12ND830
B&C 12NDL88 is an excellent driver but T/S parameter are not ideal for this box, but it should work.
You need a driver that is suited for horn loading (in this box). Typically it needs a high BL product and relatively low moving mass. It must also have sufficent Xmax to be able to produce full SPL with a nominal crossover point of 100Hz.
If you choose a driver that is designed for bass applications the response will typically have large peaks and troughs in this horn.
Newer drivers designed with FEA optimized magnetic circuits, demodulating ring(s) to reduce distortion, optimized non-linear behaviour etc. will be better.
Here is an example of the tests and measurement that you can do - https://www.audioxpress.com/article/test-bench-b-c-speakers-21ds115-21-inch-woofer (an excellent B&C 21" bass driver)
