Diffusers

I'm currently constructing a modified QRD-13.  I have made the depth 20", for more effective low frequency response.  I'm considering making two QRD-11's to place in back of my listening chair.  A while back, I saw a Utube video of a guy that made some "finless" or walless diffusers.  Has anyone seen of heard of these diffusers?  I have tried to find the video, but have been unsuccessful. I have absorbtion panels and thought if I placed the finless diffusers in front of them, it would let the sound be diffused, as well as absorb some of the low frequency.