For a basic HoloNet set-up you only need one projector, if you would like an even bigger image or make the image brighter you can blend more than one projector. In terms of which projector to use, the decision is based on your staging environment for example, if there is ambient light around where you want your hologram then you would need a more powerful projector, whereas if you are working on a small HoloNet in an almost blacked out room you could use a smaller one.