TAP-plugins
Tom's Audio Processing plugins
for audio engineering on the Linux platform

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## TAP Rotary Speaker

This plugin simulates the sound of rotating speakers. Two pairs of rotating speakers are simulated, each pair fixed on a vertical axis, with their horns spreading the sound in opposite directions. The two pairs of speakers are rotating with different revolutions (frequencies). The incoming sound is split into a low and a high part (with a low-pass and a high-pass filter, using a crossover frequency of 1 kHz). The low part is fed into the "Rotor" pair of speakers, and the high part into the "Horn" pair. A pair of horizontally aligned microphones is used to pick up the resulting sound. The distance of the microphones (the width of the stereo image of the effect) is adjustable.

### General information

Unique ID | 2149
I/O ports | 2 inputs / 2 outputs
CPU usage (44.1 kHz) | 8.5%
CPU usage (96 kHz) | 19%
Hard RT Capable | Yes
In-place operation | Supported
run_adding() function | Provided

### Usage tips

For every speaker pair, two physical effects are simulated. First, in the situation when one speaker is behind the other one (from our point of view), the speaker that is behind has lower volume (because of the distance), the one in front of us has higher volume. At this moment, the speakers have no velocity in our direction, so no pitch shift is perceived. Second, when the two speakers are at the same distance from us (after a 90 degree turn), they have the greatest velocity in our direction. One is rolling away, resulting in its pitch lowering caused by the Doppler effect. The other one is coming near, so its pitch will be perceived to be higher.

To set the rotating speed of the "Rotor" and the "Horn" pair of speakers, use the "Rotor Frequency" and "Horn Frequency" controls. Remember that sounds under 1 kHz will be fed (mostly) into the "Rotor" pair, and sounds higher than 1 kHz will go (mostly) into the "Horn" pair. You can adjust the stereo width of the effect via the "Mic Distance" control. The higher this setting, the wider the stereo image will be. Finally, you may adjust the mix of sounds coming from the "Horn" and "Rotor" parts with the "Rotor/Horn Mix" control. At a setting of zero, only the sound coming from the "Rotor" is heard; when set to 1, only the "Horn" sound is heard. The default setting of 0.5 yields an equal mix of "Rotor" and "Horn" sounds.

The settings shown in the above screenshot should provide a good starting point for your own experimentation.

### Summary of user controls

name | min. value | default value | max. value
--- | --- | --- | ---
Rotor Frequency [Hz] | 0 | 0 | 30
Horn Frequency [Hz] | 0 | 0 | 30
Mic Distance [%] | 0 | 25 | 100
Rotor/Horn Mix | 0 | 0.5 | 1
latency | latency time is 48 ms, value depends on sample rate

### Notes

Rotary speaker effects usually deal with the finite mass of real speakers, so when the user changes a speed setting, gradual acceleration of the corresponding speaker pair is simulated. TAP Rotary Speaker does not implement this, because if needed, this effect can easily be produced on a mix using Ardour automation.