Who said “ flat freq response “ is the best?

I think most music lovers and audiophiles can agree that there is no such thing as “flat” anything - especially speakers. Although, it is probably a good thing not to have prominant peaks or dips in a speakers’ response. That said, I believe that the key ingrediant to great sound is the room itself. Assuming your equipment is well matched, and you are at a certain price point, you can get more bang for buck in room tweaking than in component changes.
I have 2 systems that I listen to frequently.  The one with superior room acoustics sounds better, no matter which equipment I use in it.

Come on people. Speakers’ frequency response is almost always specified along the lines of 40 Hz to 16 kHz on axis + - 2dB. Their sensitivity is almost always specified along lines of 92 dB for 1 Watt at 1 meter. Just like stereo cartridges are usually specified along the lines of 15 Hz to 20 kHz +- 1dB.

@geoffkait 

For everyone,  geoff is accurate,  speakers publish their spec's with a frequency response and a variance within that response. 
Exceptionally flat speakers are normally rated Plus or Minus 1 db.  Anything that is typically more that plus or minus 3db is normally not considered audiophile,  although that certainly is not cast in stone. 
Today,  Many speakers are rated at a flat 2.83v input rather than 1 watt 1 meter.  For accuracy,  you need an accurate impedance, an accurate response curve and an accurate sensitivity rating. 

@ieales I've long had a mistrust of the press and regard it mostly as entertainment value only.

It would be interesting  to hear why you think phase has been largely ignored, and what did Heyser say about it? Thanks.