The Doppler Effect
The well known Doppler Effect is a major contributor of high rotor speeds for high frequency (the horn) but does not account for the richness for low frequency or when the rotor slows down:
- The HORN (high frequency) at high speed produces the Doppler Effect.
- The HORN (high frequency) at low speed has no Doppler Effect because the horn is going too slow relative to the speed of sound to produce a discernable shift in frequency.
- The BASS (low frequency) at high or low speed produces no Doppler Effect. The drum is too small because the wave length of the bass frequencies is too long and because the drum is going too slow relative to the speed of sound.
When the source of the sound is ORBITING very slowly inside the cabinet, you hear a very distinct sound. That sound is not the Doppler Effect, it's the phase shift of multiple paths, differential delays and cancellations outside the cab that is reaching your ear.
- This sound is called chorale because you're hearing multiple reflections of the sound due to the differential delays induced by the cabinet and the beaming of the sound of these differentially delayed sources.
The very little Doppler EFFECT in low speed of the horn moving cannot be heard. Sound displacement (fast movement) is what creates the Doppler Effect. The sound moves at the same fast speed all the time. That's what makes Doppler work.
The Doppler Effect only happens when the sound source is running fast. When the source of the sound, the horn in the cabinet, goes very slowly it's producing very, very little Doppler Effect.
- Whatever very little Doppler Effect happens with slow movement, it's so low in frequency modulation that it cannot be discerned by the human ear.
Differential delays in our ORBITED speaker system is all produced electronically with the cancellations happening outside in the air just like with the traditional rotary cabinet.
We at 
Amplification discovered this
with one of our initial experiments was where we did nothing but change the frequency
as with the Doppler Effect. It sounded horrible.
- Without these differential delays in the four different paths, the real traditional rotary effect cannot be heard. All that is heard is the tremelo effect; only the pitch varies. The sound is not rich at all.
The labels on the half-moon switch explain this very succinctly. The high speed is called tremolo because of the variation in pitch due to the Doppler Effect
At the slow speed on the half-moon switch there's no Doppler Effect that you can hear. It's not discernible.
- Whoever labeled the half-moon switch knew what they were talking about. They recognized the effects. This info can also be found in learned technical publication.
Back to Technology
Why ORBITED?
Rotary Speakers also ORBIT
It's all about the resonances bouncing inside the box... or is it?
One More Note
How the ORBITED speaker is different from Electronic Simulators
Mic Placement for a Rotary Cabinet
Mic'ing a Rotary Cabinet on Stage
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