Batman wrote:Hey, I've always wondered, how come Model 2 housings always have three louvers (Whereas Model 5 & 7 housings always have two.)? Are there some kinds with dual rotors or something?
The Model 2's rotor is a flow-through design, and takes in air not only through the top intake cone (like most vertical sirens do), but also through the bottom across the motor, thus the need for a third louver near the bottom of the housing. Model 5/7s do not need this third louver since they have a closed-bottom rotor and only take in air from the top.