MAKE a VOLUMETRIC PROJECTOR from JUNK

Step 2 Start Over-Get an eyeglass lens

Get the biggest eyeglass lens you can find, maybe one that has not yet been cut to fit in frames.
An assortment might be better. Uncut stock lenses look like magnifying glasses except they have
a concave side. Or just play with someone's glasses for a minute.

Get an LED and a watch battery and light it up. Hold the "glasses" looking down.
Hold the LED above the glasses. Move the glasses up and down. You should see
a moveable virtual image between the glasses and the LED.

If you have a circle of LEDs and you move the glass lens up and down you get a tube.
If you have a square of LEDs you get a cube.
If you change the image while the lens moves, using a PIC with many LEDs for example, you can get any shape.

What's important is that the virtual image appears in the air above the lens,
and the size of the lens is the maximum size of the image.
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EDIT:new image+comment:
Oh... It turns out that the shinyness of this woofer is causing unexpected multiple floating images.