Effective Blower Speed
Multi-speed motors are rated at their speed on high, so high will be around 1075.  The other speeds will typically be around 100 rpm lower than the next speed, so you don't get a lot of range in that speed.  The speeds are also designed so that with the same load applied to the motor (like a fan blade), the different speeds give less power to the motor, so it naturally slows down. 

If the motor is loaded more or less than it was designed for the change in speeds will vary.  I've never tried this, but I suspect the no-load speed on low will be very close to the high speed, and you will get more separation in the speeds the more the motor is loaded.