believe it or not:
generally speaking - cats are divided into " large " [ roaring ] and " small " [ purring ]
cougars and cheetahs are the biggest of the " small " cat species
throat structures are the difference
" Roar VS. Purr
The cat family, known as Felidae, is split between bigger cats who can roar and smaller cats who purr. The roaring cats are part of the sub-family called Pantherinae and the purring cats are in the sub-family Felinae. In fact, only four species of cats can actually roar. These are lions, tigers, leopards, and jaguars. The most widely accepted explanation for the mechanism of a roar vs. a purr comes down to a bone called the hyoid, situated near the larynx. "
Purrs VS Roars: The Secret Reason Why Cats Who Purr Can Never Roar - CatTime