Rotary Speaker

The Rotator is a model of a traditional rotary speaker cabinet such as those used to create the familiar Leslie organ sound. It simulates the rotating horn (treble) and woofer (bass) along with their crossovers.

The rotors can be switched on and off, and their speed adjusted from a very low setting (0.1Hz) through the classic “Chorale” and up to “Tremolo” settings. The speed of the rotating speaker is indicated by a large flashing lamp. The acceleration/deceleration on each speaker is modeled independently, and both speakers stop facing the front when the motors are powered down. The balance between the horn/woofer can be adjusted.

Some users of rotary speakers choose to cut the deflectors off the end of the treble horn to produce a more pronounced “chopping” sound with more amplitude modulation and a less pronounced Doppler effect. In the Rotator the deflectors can effectively be removed or replaced by the flick of a switch. Similarly, the back panel of the cabinet can be removed or replaced to produce a different cabinet response.

Microphone set up is crucial to the rotary speaker effect, so three options have been provided in the Rotator. The effective microphone positions can be set to Side-Side (one either side of the cabinet), Front-Back (one at the front/back of the cabinet) or Front-Front (to reproduce the effect of a stereo pair). In the latter setting, the distance between the two microphones can be adjusted, to change the effective physical width of the stereo microphone pair.

Rotator features a simulation of the tube drive stage found in a classic rotary speaker. This reproduces the warmth and distortion introduced by such a stage, and when driven hard can produce the familiar rotary speaker ‘growl’. The tube drive is adjustable, or can be bypassed altogether. Finally, an option to introduce mains hum and its associated intermodulation distortion is provided for those who desire the true rotary speaker experience. This can be switched between UK/US mains frequencies and the amount of hum can be adjusted.

As with the real rotary speaker this effect is mono input only but produces a stereo output. If a stereo input is assigned, the two channels will be software summed to a mono input.

Rotors – Turns the treble/woofer motors on/off. When the motors are off, the speakers are both facing the front of the unit. When switched on, the motors will ramp up to the speed indicated by the Speed control. The woofer motor accelerates more slowly than the treble motor. When switched off, the motors will then decelerate to the minimum speed, until stationary and facing the front of the unit. The On/Off switch controls only the rotor speed, not the whole effect.

Speed - Controls the desired speed of speaker rotation. Its lower setting is 0.1Hz (i.e. 10 revolutions per second). The other two marked positions indicate the values corresponding to those provided on classic rotary speakers: Chorale (indicated as “chor”) and Tremolo (indicated as “trem”). Other positions on the control graduate between the values. The lamp to the right of the speed control flashes at the same rate as the treble speaker rotates.

Width - Adjusts the stereo width of the two microphone outputs, and therefore the spatial “depth” of the effect. At the “Mono” setting both simulated microphone outputs are summed equally to the left and right outputs. At the L/R setting the simulated left/right microphone outputs are sent to the left / right output channels correspondingly.

Balance - Adjusts the relative weighting of the treble/woofer speakers. At the “LF” setting, only the output of the woofer is heard. At the “HF” setting, only the output of the treble horn is heard. Intermediate positions graduate between the two.

Deflectors - Simulates the attachment (On) or removal (Off) of the deflectors on the end of the treble horn.

Back Panel - Allows for the attachment (On) or removal (Off) of the virtual back panel. This changes the simulated cabinet response as appropriate.

Mic Select - Allow for configuration of the two simulated microphone positions. Side-Side simulates the positioning of microphones on opposite sides of the cabinet. The Front-Back option simulates position at the front/back of the cabinet. The Front-Front option simulates positioning both microphones at the front of the rotary speaker. In this mode, the “Separation” rotary becomes available. This allows for the distance between the two front-positioned microphones to be adjusted, subtly changing the nature of the modulation in each output channel. Changing the Separation control does not affect the Side-Side or Front-Back options. The Separation rotary control is not available when in other modes.

Tube Drive - Controls the tube (valve) drive simulation. With the control at “On” the tube drive is active. With the control at “Off”, the tube drive is completely bypassed. The tube drive rotary control adjusts the depth of the distortion (1 = slightly warm, 11 = distorting).

Mains Hum Panel - Adjusts the level of the mains hum introduced. The hum itself is actually very quiet at “Hi”, but “Lo” makes it quieter still, and “Off” turns the mains hum off completely.
50/60 - Switches between mains frequencies typical to the UK (50Hz) or US (60Hz).