0 - 40Hz subwoofer

[tadawson]

I can't imagine that you could reverse direction fast or accurately enough. I wonder if it's 'biased'-up to half-speed, and the speed is varied above and below this?

It'd be like a 'class-A' kind of thing. I could see pulling something like that off - maybe with a PWM drive.

Joe

As I read it, they don't change the motor shaft speed at all - they vary the pitch of the blades from positive to negative, very quickly. The motor is most likely constant speed. For no sound output, zero pitch on the blades, and the motor just freewheels. There is a LOT less moving mass to deal with this way . . .

- Tim

 

[Tim__x]

I can't imagine that you could reverse direction fast or accurately enough. I wonder if it's 'biased'-up to half-speed, and the speed is varied above and below this?

It'd be like a 'class-A' kind of thing. I could see pulling something like that off - maybe with a PWM drive.

Joe

It doesn't change direction, the propeller spins at a constant speed and the pitch of the blades is varied, like many propellor planes or a helicopter.

Fan? You really mean a fan - as in Leslie speakers? Are these like powered subwoofers?

Did you follow the link in the first post?

 

[luknfur]

It doesn't change direction, the propeller spins at a constant speed and the pitch of the blades is varied, like many propellor planes or a helicopter.



Did you follow the link in the first post?

Actually.........., no. But I see what you're talking about now. I thought this was in response to Petebass' stuff.

Interesting about the reason people were assumed unable to hear below 20Hz being a result of low output. I wonder how they handle low frequencies in hearing exams. You're wearing headphones in a sealed booth there. Apparently they don't increase ouput to compensate for drop in frequency.