I know that this has been posted before but finding consistent data is frustrating. Altec 414-8B uses a ferrite magnet and the 414-8C uses an Alnico magnet. The Thiele-Small measurements are different but finding which is which is confusing. GPA has not been very responsive in sending this information. Google search has directed me to different sites with varying data. SPL sensitivity for the 414-8B is slightly different from the 414-8C (or not depending upon the source).
Any help would be appreciated. Hard to design a box enclosure without accurate Thiele-Small data.