This soundstage phenomenon is enhanced by the quality of the performance inside the listening window (loosely defined as 0 – 30 degrees off axis). It is not really related to size at all because the added frequencies of a floorstanding speaker are in the non-directional frequency range. It can be baffle related, which no doubt draws the misguided connection to size, because smaller baffles tend to be somewhat less likely to deteriorate the frequency response inside the window if no design effort is put into the issue. This being said there are lots of little speakers with horrible listening window responses and lots of larger speakers with very good ones. It comes down to whether the designer worked through this one in the beginning.
