Revolution uses advanced HRTF based models to allow sounds to be positioned anywhere in 3D space. It also emulates the delay caused by the speed of sound, creating accurate echoes and Doppler shifts.
Revolution uses a visual display to show and change the position of the sound in relation to the listener, but control via traditional knobs is also supported. All parameters can be automated, and extensive CV control is available.
Revolution also has a feedback control to allow simple echoes to be achieved, and a pre-3D audio output to allow the user to create more complex echoes using multiple instances of the device.
Primer on 3D audio and HRTF
Revolution uses HRTF (Head Related Transfer Function) algorithms to move audio around in 3D space. A Head Related Transfer Function describes how audio is affected by our own heads, both by the delay caused by the separation of our ears, and the filtering caused by the absorption of sound on the skin and skull.
Our brains use these delays and changes in spectrum to give clues to the position of the audio source.
Revolution makes use of these changes to trick the brain in to believing that a sound is placed outside of the normal left - right audio field that standard stereo panning allows.
Why use 3D audio?
One obvious reason is for effect – a sound coming out of 3D space may surprise the listener and add variation to a track.
Another important use is to extend the stereo field for people listening on headphones. Listening to music on headphones is more common than ever, but normal stereo panning only allows an audio source to be placed between the ears. Using 3D audio can create the illusion of the music coming from speakers around the room, or even a live band.