http://www.stereophile.com/content/bowers-wilkins-683-s2-loudspeaker-measurements#PeIW9BsGI25szTum.97
Listening-window FR from 200Hz-10kHz is about -6dB, +2.5dB, so total deviation is about
8.5dB, which is typical mediocre B&W frequency response, IMO. And, of course, as usual, the off-axis FR is pretty bad like all B&W speakers, even their $30K B&W 800 speakers.
As long as they sound great to you, that's what counts.
But if you ever think, "Hmm, I wonder if I can get better sound in my system because the on-axis and off-axis FR of these speakers are not good?", then it's not so good.