Who said “ flat freq response “ is the best?

@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.

A further word on J Gordon Holt.  He conducted most of his listening evaluations utilizing master tapes which he made of acoustic classical performances.  And he seemed to posses a very good auditory memory.  That allowed him to make value judgements on how well given components came to reproducing those live creations.  How many reviewers today do anything similar?

I offer this since many readers may be too young to have much appreciation for Holt and what he meant to audio reviewing.  He cared about electrical performance, but his ears were the final arbiter.

Speakers posting their frequency response often are challenged by measurement (for example, every speaker reviewed in Stereophile), with peaks and valleys here and there all over their range. This might not mean much if the designer listened to them, which is generally the case. Also the frequency response noted by manufacturers is often utterly incorrect...I have a pair of very coherent, great sounding Silverine Preludes, which list the low end as -3db at 38hz, when at that point they're more likely -10db at least. My Klipsch Heresy IIIs are rated to around 58hz and that's pretty much exactly right...my subs take over at that point so it's all good.

IMO, phase has been ignored because so few people have heard a properly phased system. Designers who don't understand the importance choose to ignore it and the media play along. Few systems are phase correct to begin with and those that are rarely setup correctly. Very few people who buy HiFi ever hear unamplified music in a good hall and thus have no reference to an acoustic space.

The Absolute Sound recently reviewed a time-aligned 2-way loudspeaker with 1st order crossovers. Unless the drivers are perfect, it is simply not possible to achieve minimal phase error with that design.

The AES has an anthology of Heyser's work on Time Delay Spectrometry.
It's long @ 279 pages: http://www.aes.org/technical/documents/openaccess/AES_TimeDelaySpectrometry.pdf 

Stereophile opined "Essential reading for the informed audiophile: the AES anthology of the late Richard Heyser's writings" on https://www.stereophile.com/content/2011-richard-c-heyser-memorial-lecture-where-did-negative-freque...