Ouch, golx!
infinite baffle otherwise known as the closed box designIB, closed boxes, ported, OB etc are all different...
the lowest frequency transmitted depends on the smallest(!) distance between driver edge and baffle edge, thats why they are usually circular??? Were they circular, there would NO smallest distance. A circular baffle has the worst response pattern and is rarely used. Maybe your eye caught a sphere somewhere? The response pattern is much better there. BTW the smallest diametre is a valid point -- if that's what you're referring to.
they stopped being used sometime prior to WW2You have me baffled! Cheers!