Why does it need headphones?

Because the whole effect is the difference between what each ear receives. With two speakers, each ear hears both of them, the small interaural delay is filled in by the room and by the listener's own head, and the movement collapses into an ordinary pan that any stereo mix has.

What does the depth control change?

The maximum delay applied between the ears, which is about two thirds of a millisecond at full depth. That interval is close to the natural arrival-time difference for a sound at one side of the head, so reducing it weakens the sense of direction until the effect becomes a simple panning sweep.

Does a stereo source survive the conversion?

Its stereo image does not, since the source is averaged to mono before being spun. That is inherent to the effect: the rotation supplies the spatial information, and leaving the original image in place would compete with it rather than add to it.

Why is a slower rotation more natural?

Because a sound circling the head several times a second is heard as an effect rather than as movement, and its direction becomes a blur. A revolution taking eight seconds or more reads as a source travelling around a room, which is what the effect is imitating.

Does it create height or front-to-back depth?

No, it works on one horizontal circle. There is no head-related transfer function, so no elevation is produced and distance is conveyed only by the movement itself rather than by any change in tone or directness.

8D Audio Converter

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8D Audio Converter spins a recording around the listener's head in circles, using equal-power panning and a tiny delay between the ears. Headphones are required, because the effect lives entirely in the difference between the two channels.

What is 8D Audio Converter?

Set how long one revolution should take and how deep the movement should be, drop a file, and convert; the source is downmixed to mono and spun, and the output is always stereo.

The two controls:

A rotation time from two to twenty seconds for a full circle, defaulting to eight.
A spatial depth from nothing to a hundred percent, defaulting to eighty.
The reported figures: one revolution per chosen time, the depth, and the delay that depth produces between the ears, up to about two thirds of a millisecond at full depth.

Two cues are generated together, and both are needed. The first is panning: the gain applied to each side follows a cosine and a sine of the rotation angle, which is the equal-power law, so the total energy stays constant as the source moves and the sweep does not appear to dip as it crosses the centre. The second is a delay of up to about two thirds of a millisecond applied to the ear that is further from the source, and it is the more important of the two. That interval is close to the difference in arrival time between a person's ears for a sound coming from directly to one side, so the ear reads it as direction rather than as an echo, and both ears receive the sound within the window in which the brain fuses the two arrivals into a single event. The delay is also asymmetric within each revolution: as a side's gain falls toward zero, its delay lengthens toward the maximum, and as the sound comes back round it shortens again, which is how one continuous signal manages to sound as though it passes in front of the listener and then behind. Because all of that happens across the two channels rather than within either one, the downmix to mono at the start costs nothing, and the output has to be stereo for the effect to exist at all. Headphones are the right way to listen to it and speakers are the wrong way: with two speakers in a room, both ears hear both speakers, the interaural delay is filled in by the room and by the head's own shadow, and the effect collapses into a plain pan. Slower rotations also sound more natural, since a fast spin is heard as an effect rather than as movement.

What it does not do:

No head-related transfer function, so no height information is created.
No front or rear distance cues beyond the rotation itself.
Genuine stereo sources are reduced to mono before processing.
No automatic rotation based on the material's tempo or structure.
The effect disappears on speakers.
Output is sixteen bit WAV.

Use it for the sound it is named after, which listeners recognise from music uploads: a track that sweeps past the ears once per revolution, or a spoken passage that circles the listener for a moment of interest. When the movement should be a one-off pass rather than a continuing orbit, the doppler effect simulator sends the source past at a chosen speed, and when the space should be wider without any movement at all, the stereo widener works on the image in place.

How to use 8D Audio Converter

Drop an audio file onto the panel and let it decode.
Choose the rotation time, using a longer one for a subtler sweep.
Set the depth, which controls the ear delay and therefore how convincing the circle is.
Convert the file and listen on headphones, since the effect is invisible on speakers.

When to use 8D Audio Converter vs related tools

8D Audio Converter is the tool for the rotating, headphone-only movement that gives the effect its name. Doppler Effect Simulator sends a sound past the listener once at a chosen speed rather than around them. When width rather than movement is what a mix needs, Stereo Widener changes the image in place, and Surround Sound Simulator builds discrete rear channels for a four-speaker system.

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