I think this is a very interesting point. I have a pair of B&W 705s, probably from about the same era as the 805s's reviewed here. Based on the Stereophile review measurements (
https://www.stereophile.com/content/bw-705-loudspeaker-measurements), they seem to have frequency response similar to the earlier 805 Nautilus cited above in this thread, but like the Nautilus response curve posted above, there are still signs of some dips between 1 and about 3-4kHz.
Independently of the Stereophile measurements I have EQ applied (roughly, via an actual equalizer and an SPL meter) to give relatively smooth in-room response from my listening position. When I run SPL tests I do notice a 1-2dB dip in response at 1kHz, but nothing more than that, and no dip at 4kHz - in fact, for whatever reason my speakers have always read as up, not down, at 4kHz, even in a previous, very different listening room.
Subjectively, my impression always has been that these are clean-sounding speakers (low distortion from the drivers); and that some vocals are spookily present while occasionally on some recordings some of the vocals sound a little recessed (and if I didn't have that 1-2dB EQ boost at 1kHz maybe more vocals might sound recessed).
I also have always been impressed by how dynamic and pleasant the speakers are at relatively low listening volumes. I listen in the 75-85dB peak range usually, which is somewhat low by what I take to be typical stereo home enthusiast standards. And I imagine I listen at levels 15-30dB lower than most music is mastered at.
So I would not be surprised if even my roughly EQ'd setup, if measured using Spinorama, might show up as slightly smiley-faced (although again, my EQ is adjusted with the goal of linear in-room response), which could explain why the speakers seem to come to life nicely even at relatively low volume.
