The graph below is a comparison of the frontwave and the backwave of a B&G RD75, no baffle, measured at 3 meter and 1 meter in room. Large reflections gated out, some minor reflections stayed in.
In both situations the backwave is significantly different than the frontwave, probably because of the open cell foam that is covering the slots in the back of the ribbon. The backplate of the ribbon is also flat versus a small "horn" section in the front.
Remarkable is the almost straight 6dB/octave line from 200Hz to 800 Hz in the 3 meter measurements, illustrating the dipole (baffleless) cancellation. This cancellation is not as pronounced in the 1 meter test, giving raise to the "false" impression that one could do without baffle. Doesn't seem the case however at a real listening distance.
Similar measurements were performed on a Carver driver. This driver as a felt strip on the back that with some peeling is removable, hence the test front and back with felt and front and back without felt. The felt provides apparently some "damping" at the low end. The dipole cancellation with and without the felt strip is different. Noticeable is the bump in the response between 200-300 Hz that is apparently smooth'd out with the "dampening" action of the felt strip. There are no major differences in the high as seen with the B&G driver.
