This paper documents explorations into an alternative platform for immersive and affective expression within spatial mixed reality installation experiences. It discusses and analyzes experiments that use an advanced LED cube to create immersive, interactive installations and environments where visitors and visuals share a common physical space. As a visual medium, the LED cube has very specific properties and affordances, and optimizing the potential for such systems to create meaningful experiences presents many interlinked challenges. Two artworks exploring these possibilities are discussed. Both have been exhibited internationally in a variety of settings. Together with this paper, the works shed some light on the design considerations and experiential possibilities afforded by LED cubes and arrays. They also suggest that LED grids have potential as an emerging medium for immersive volumetric visualizations that occupy physical space.