What is the effect of different shapes of the surround of passive radiators

How does the shape of the rubber surround affect the acoustic performance of a passive radiator? What are the benefits over normal design?
I have attached some related images with such passive radiatos.
I assume that it must have advantages over normal forms as well-known brands like Bose implement it in their successful products.

I searched for a while but couldn't find anything on the subject. I also noticed that it only seems to have to do with passive radiators, not speakers.
 

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