Rotary Speaker Simulator

A rotary speaker simulator also known as a Leslie speaker simulator, is a device that attempts to recreate the sound of a Leslie speaker used extensively to amplify and modulate the raw organ tones produced by (though not exclusively) the tonewheel organs made by the Hammond Organ Company, and invented by Don Leslie.

While many analog devices have been touted as rotary speaker simulators, including but not limited to the Mini-Deja Vibe, Mojo Vibe, Rotosphere, Rotovibe, and Uni-Vibe, due to the difficulty in mimicing complex acoustic systems with large delays using analog circuitry, these tends to produce output that may be pleasing, but often easily distinguishable from a real Leslie.

Thus, the most accurate rotary speaker simulators tend to be digital, using modeling algorithms to model the relations between the rotating horns and the bass baffle, and well as how the sounds bounce around the cabinet. As a Leslie also has an amplifier section, most of these typically have overdrives to simulate the sound produced by overdriven tube amplifiers and so produce a distortion that is often cited as (in the case of tube amplifiers) musically pleasing. These pedals and/or rack units usually accept keyboard and guitar input, as many guitarists as well as organ players have found the modulated sound produced by these rotary speaker simulators enhances their instruments' sound.

In 2006, Boss released its first stand-alone rotary speaker simulator, the RT-20. Roland were already producing modelled rotary speaker simulation DSPs in their VK-7 drawbar organ keyboards several years earlier, and later on their VK-8 organ keyboards, VK-Combo organ and various home organ models.

Line 6, as well as DLS, also use modeling technology on their rotary speaker simulator. Eventide also have a rotary setting on their ModFactor stompbox. The ModFactor was mentioned in Guitar Player magazine, with the quote "worth the entire $399 just for its rotary". Around August 2009 a German company, Neo-Instruments brought a new simulator, the Ventilator, to market that also models the complex rotary sound produced by a Leslie speaker cabinet as heard when being recorded through the typical three microphone array that is used in recording studios and off-stage to capture its complex modulation.