Compression Drivers

I have the opportunity to get my hands om a pair of TAD 4002 compression drivers without the original beryllium diaphragms , they have been replaced with radian diaphragms instead , the drivers are label as 16 ohms , but upon reading the ohms it only shows 4ohms , what significance has this in terms of having 8 ohms bass speakers units and crossovers that are 8 ohms as well ? anyone can share some light on this matter ?