Two quick measurements showing some of the interactions when the backwall is moved closer to the dipole. Just kidding. I kept the location of dipole and microphone the same and used a 8' by 8' drywall partition to move around, just didn't want to loose the position in the room ;-)
Regardless of the distance between dipole ribbon and the microphone, having the backwall close to the ribbon driver is not a good idea as shown by the two plots on this page. In both cases is the yellow plot, 1/4 meter between driver and backwall, the less desirable one.
