How do 12-port Model 5/7s sound different than STH-10s?

[Allenorgan42099]

Up close, I think Model 5/7s are more raspy sounding than STH-10s, which are more smooth and throaty. Far away it is hard to tell the sound apart. Do you agree with that? One time I was at one of my grandparents' houses and heard an unknown 12-port siren in the distance, but it was too far away to tell what kind it was.

[Andys Live WX]

The 5/7 rotors produce that third octave because there are 4 blades in a square across from each other that are slightly larger than the others.
Also STH-10s tend to wind down slower because of their larger diameter heavy rotors. 5/7s have smaller rotors that are lighter.

[Daniel]

The difference in timbre comes mainly from the projector horns.

[holler]

It's because of the rotor design. As Andy said the STH 10 has 12 full length vanes that go all the way to the hub. The 5 only has 4 full length vanes, the rest stop short of the hub.