Rack Extension for Propellerhead Reason
User Manual
Version 1.0
INTROD U C TION
Revolution is a 3D audio effect for Propellerhead Reason. It allows the user to place a sound anywhere in 3D
space, and to move that sound around in real time with the associated Doppler Effect.
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.
PRIM E R ON 3D AUDIO AND HRT F
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 – in
reality we are more sensitive to changes in position that absolute location – that's why we will sub-consciously
move our heads when trying to locate a sound.
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 U SE 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.
LIM I T ATIONS
Unfortunately, every head is different, so Revolution uses a composite of HRTF models recorded using a large
group of people to create an 'average' model that produces a usable 3D effect for most people. Some people
will find the effect more prominent than others, so test your final mix with multiple listeners.
The HRTF effect is most effective when listened to on headphones. Studio monitors work reasonably well as
they have good stereo separation, but the effect may be lost on other speaker setups.
Any stereo input to Revolution is converted to mono to create a single sound source. If you wish to maintain
the stereo signal, then 2 instances of Revolution are required.
The stereo output must be maintained throughout the mix chain – that means keeping panning to centre, and
ensuring that any compression or limiting is done in stereo linked mode. Any reverb or delay required should
ideally be performed before Revolution.
Whilst Revolution offers an elevation control, our brains are less sensitive to locating the height of a sound
source. (There are no changes in audio delay due to elevation which is the main cue we use for location.)
The 3D effect will not work with mono speakers (such as mobile phones) although the 3D audio will mix down
to mono reasonably well.
The minimum distance from the listener is 2 metres, which gives around 6ms delay. The algorithms cannot
produce lower delays without excessive CPU load.
US A G E I N STRUCTIONS – FRON T P A N E L
SP E A K E R POSITION
The green speaker represents the source of the audio. It can rotate around the listener, and move further or
closer to the listener.
Changing the Angle knob will rotate the speaker through 360°. Alternatively, grab the speaker on the display
with the mouse and move it around the centre position.
Increasing the Distance knob will move the speaker further from the centre. Alternatively, grab the speaker
with the mouse and move it further from the centre. This increases audio delay (due to the speed of sound),
and reduces audio volume. Distance can range from 2 to 100 metres.
Distance Attenuation controls how much the volume is reduced due to being moved further from the listener.
At 100% it will give a realistic attenuation, at 0% it will not reduce the volume for any distance.
The Zoom slider zooms the centre display in and out. At minimum zoom, the display represents 100 metre
radius, at maximum zoom it only shows 10 metre radius.
SP E A K E R ELEVATION
The Elevation control adjusts the height of the speaker above or below the listener. It ranges from -45° to
+45°.
FE E D B ACK
The Feedback knob allows a percentage of the delayed audio to be fed back into the source to create simple
echo effects. Note that the audio is tapped before 3D algorithms.
DRY – WET
The Dry – Wet knob controls the mix of original and 3D audio. This can be useful for creating echo effects
where you want the audio to appear to bounce of a nearby object – in this case you would hear both the
original audio, and a delayed version of that audio from a point in 3D space.
US A G E I N STRUCTIONS – REAR PA N E L
SP E A K E R POSITION
The Angle and Distance CV inputs allow you to offset the position of the speaker.
When these CV inputs are used, a second ghost speaker will appear on the front
screen. This ghost is the actual position of the speaker used in the 3D calculations.
When you use the mouse to move the speaker, you are moving the brighter
reference speaker. The ghost speaker will always use the CV inputs as an offset
from the reference.
The Elev CV input will offset the elevation of the audio source.
The Shift Perpendicular CV input will move the audio source perpendicular to its current position. If the
speaker is currently at 0°, then this input will move the speaker left and right. This input is very useful for
creating 'fly by' Doppler effects. Again the calculated position is shown using the ghost speaker on the front
display.
CV O U T
The Angle CV output gives a control signal that represents the current angle of the speaker. One use for this is
to pass this signal into the Angle input of a second Revolution device, and then apply an offset using the Angle
knob on the front panel.
The Distance CV outputs the calculated distance from the listener.
Of course these CV outputs can be used to control many devices in Reason, and you can then use the front
display as a unique control surface.
PRE- 3D
The Pre-3D audio outputs the delayed and attenuated audio before the 3D effect is applied. This is useful for
when multiple Revolution devices are chained to make audio appear to bounce around 3D space. See the
included Crazy Echo combinator patch for an example of this.
AU D I O IN
The Left and Right inputs are for your source audio. If a stereo signal is used, it will be mixed down to mono
before the 3D effect is applied.
AU D I O OUT
The Left and Right outputs contain the processed 3D audio. It is important that the panning on the mixer for
this audio is kept in the centre position. Applying further effects to this audio may reduce the 3D effect.
REC O R D I N G MOTION
By default, Revolution does not create a Reason track. If you wish to record the motion of the speaker, then
you must right click on the device and select the 'Create Track for …' option.
Once this is done, you can record the motion of the speaker from either the knobs or by using the mouse on
the display. Moving the speaker in the display will automatically create Angle and Distance automation lanes.
REV I S I ON HISTORY
V1.00
Initial Version
CRED I T S
Design and coding by Richard Harvie, DLD Technology Ltd – http://www.dldtechnology.com
Logos and additional graphics by Steven James, Chimera Creations - http://www.chimeracreations.co.uk
Additional patches by Linus Wileryd, Navi Retlav & Simon Bader.
Thanks to all that have helped test Revolution on the DLD beta test group.
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