Space...the Final Frontier SIDEBAR 3
While I don't disagree with J. Gordon Holt's feeling that many "audiophile" loudspeakers are designed to have a degree of response shaping---though I can think of as many that tilt up as tilt down---it's only fair to point out that, by his own admission, JGH has never actually auditioned either the Westlake or the Acoustic Energy loudspeakers he uses as examples in developing his hypothesis.
He does imply that predicting a loudspeaker's sound quality from its on-axis frequency response is not a trivial matter. I agree, so here are my interpretations: Looking at the two graphs of the axial response, I fail to see that the differences are as clearly marked as JGH describes. Yes, the AE3 (fig.1) does have a clockwise tilt, looking through the general lumpiness to consider the speaker's exaggerated upper bass and slightly suppressed top octave before the ultrasonic tweeter resonance. It does have a slight presence-region depression, which might give rise to a feeling of image distance, but it also has a somewhat elevated mid-treble, which will add a touch of brightness. The Westlake's axial response (fig.2) is significantly smoother and flatter overall, but it might also be judged to be just a tad tilted down. It does have a little more top-octave energy on axis than the AE3, however. Its nearfield port and woofer responses are also not nearly as exaggerated in level as the Acoustic Energy's.
Fig.1 Acoustic Energy AE3, anechoic response on tweeter axis at 45" averaged across 30 degrees horizontal window and corrected for microphone response, with nearfield woofer and port responses plotted below 300Hz.
Fig.2 Westlake BBSM-6F, anechoic response on tweeter axis at 45" averaged across 30 degrees horizontal window and corrected for microphone response, with nearfield woofer and port responses plotted below 300Hz.
Contrary to Gordon's statement, I actually commented negatively on this aspect of the AE3's balance in my 1992 review. I noted that the AE3 sounded "too mellow," with a "thickened, too heavy" bass region that lacked clarity. "Quantity is one thing, but quality is another," I wrote, adding that "the bass overall seemed somewhat exaggerated in level, which in itself can be quite pleasant, but this was accompanied by a feeling of detachment from the lower midrange that emphasized the disparity in level." I also found the mid-treble a bit exaggerated, but I very much liked the speaker's good midrange transparency and the excellent sense of ambient space inherent in its soundstaging. This was offset by a lack of image depth in absolute terms, the speaker's depressed presence region notwithstanding.
While the Acoustic Energy AE3 did not sound as neutral as better speakers in its approximate price range---the Thiel CS3.6 or Spendor S-100, for example---I felt its balance faults were significantly offset by what it did right. As JGH correctly describes, however, I did feel that the Westlake BBSM-6F had a forward, vivid-sounding, midrange-dominant balance, with a shelved-down bass region. Although I found that the Westlake's upper treble sounded clean, there were some resonant-type colorations in the lower treble that I found added hardness to the sound, and there was significant "vertical venetian blinding" apparent. (footnote 1 I also felt that the Westlakes' soundstaging was mediocre, with limited depth and a noticeable broadening of central images.
Not all of this behavior, of course, can be predicted by axial response curves, which is why Stereophile's loudspeaker reviews also indicate the manner in which that response changes off-axis in both vertical and horizontal planes. Though the direct sound from the speaker plays an important role in determining sound quality, in a real room, as opposed to an anechoic chamber, the off-axis behavior will also affect the perceived balance.
Footnote 1: This phrase, coined by J. Gordon Holt, means that the listener can hear the sound undergo numerous cancellations and reinforcements in the treble as she moves her head slightly from side to side---a distinctive comb-filtering effect.---JA