Maybe they're homemade tube traps a la Jon Risch? If so, each cylinder may essentially represent two chicken wire cylinders with fiberglass between them, an air space in the middle, and three MDF or other composite material discs (two end caps and a smaller middle support). The airspace is supposed to help bass absorption. In any case, yours look like each one represents two different diameter cylinders stacked. If there's no reflective membrane (like saran wrap), they'll primarily act as absorbers, although how effectively so would depend on cylinder diameter and fiberglass thickness. Anyway, you can probably try putting them in the corners and seeing what happens.
If there is a reflective membrane, then they may act more as diffractors than true diffusors, but this might only be at higher frequencies.
