Automate a pan knob from left to right and back, and most people describe the result the same way: the sound gets louder in one speaker and quieter in the other. It does not sound like something moving. That is because a pan knob does exactly one thing. It changes the level each loudspeaker gets. Nothing else about the signal changes.
A real source travelling past you changes in several ways at once, and your ears use all of them. This post goes through what those cues are, why level alone is a weak one, and how Locomotion, a 3D auto-panner, renders the rest of them so a part sounds like it is going somewhere rather than sliding between two speakers.
What a pan knob leaves out
Think about someone walking a guitar amp across a room while it plays. Several things happen to the sound that reaches you, and only one of them is level.
Distance changes level and air together. As a source moves further away it gets quieter, but it also loses some of its top end and directness relative to the room around it. Closer, it is louder, brighter and more present. A pan knob moves the level between two channels while the distance never changes, so the image slides along a line at a fixed distance from you.
Motion changes pitch, slightly. A source moving towards you compresses the waves that reach you, and one moving away stretches them. That is the Doppler effect, and on a moving source it is a small, continuous wobble in pitch as the speed toward or away from you changes. Static panning has none.
Each ear hears it differently. When a sound is off to one side, it reaches the far ear a fraction later than the near one, and the head shadows the far ear, so it arrives there a little duller. Your brain reads that time and tone difference as direction at least as much as it reads level. A pan knob changes level only, so the cue your ears trust most is missing.
Behind you is a different sound from in front. The outer ear shapes sound differently depending on whether it arrives from the front or the back. Two loudspeakers in front of you cannot place a source behind your head by level alone.
Put all of that together and the gap is clear. A pan sweep is a level sweep. A moving source is a change in distance, pitch, timing between the ears and tone, all tied to one path through space.
How Locomotion turns a pan into a place
Locomotion runs a phase around one lap of a path and moves the image along it, with every cue a real moving source gives: level and air that change with distance, a touch of Doppler, the far ear hearing it a little later and duller, and a way of reading "behind you" on loudspeakers that works in mono too. All of those live on one control.
DIMENSION is that control. The store describes it as every cue a real moving source gives, in one hand: distance, proximity, Doppler, the ears and behind the head. At zero, the image is a level pan, exactly what a pan knob would do. Turn it up and the other cues come in, so the same path stops being a balance change and becomes movement through a room. The quickstart advice is to turn DIMENSION up until the image leaves the loudspeakers.
PATH decides where the source goes. There are six:
- CLASSIC, side to side, the old stage trick.
- CIRCLE, a ring in front of you.
- FIGURE 8.
- ORBIT, around your head.
- BOUNCE, hard left and right.
- RANDOM, a new spot each lap.
A pan knob can only ever do the first one. CIRCLE and ORBIT are where DIMENSION earns its place, because a ring has a near side and a far side, and ORBIT passes behind the listener.
DEPTH and IMAGE OFFSET decide how far the path reaches and where its middle sits. DEPTH at half with OFFSET to the left gives a ring around your left ear. REVERSE runs the path the other way.
WIDTH scales the field. Past the loudspeakers, it pushes the far side out with a bleed that thins in mono rather than cancelling. The quickstart suggests WIDTH past 100 for a part that should wrap around the listener. MIX blends the moving image against the input.
SPEED runs free from 0.02 to 20 Hz, or locks to the host from 8 bars down to 1/32. Synced, the lap is read off the host's bar position, sample-accurate, so it survives loops and transport jumps and two instances never drift. START sets where on the path a lap begins, and TAP TEMPO sets the lap to a tapped interval.
Two details matter in a real mix. First, a stereo input is treated as one image, not two channels: the two sides keep their native spacing as the image moves, read off the input's own correlation, so a wide synth stays wide while it orbits. Second, Locomotion has 4 ms of latency, reported to the host, with bypass and MIX aligned, so switching it in or out moves nothing in time.
The IMAGE readout draws the image left to right as a blob that gets wider and brighter the closer it is: DIMENSION's distance cue made visible.
A good starting point is a send with MIX all the way up, SYNC on, one bar per lap. A slow CIRCLE under a pad with DIMENSION up moves the part through the room; ORBIT on a reverb return with DEPTH wide gives a static mix something that travels around the listener. Step through all six paths with the band playing; the one that reads best is often not the widest.
What to try
Take a pad or an electric piano part and start a 14-day free trial of the full version. Put Locomotion on a send with MIX all the way up, PATH on CIRCLE, SYNC on and one bar per lap. Leave DIMENSION at zero and listen: that is a level pan. Then bring DIMENSION up slowly over the same four bars and listen for the point where the part stops sliding between the speakers and starts moving through the room.