Well, in fact, while you can't 'image' below 90Hz, you can get intense changes in envelopment. This absolutely requires more than one sub.
That's way, way below any transition frequency, and you can't claim "bass quality" until you make that listening room sound as "wide" as the church you started in.
Sorry, but we have to disagree, and there are discussions thereabouts this board detailing others' experiences with it.
Reducing seat to seat variations is only the start.
I don't think we disagree, more like we just have different priorities. In decades of double-blind subjective evaluations it became very clear early on (1985/86) that bass extension, by itself, correlated with sound quality ratings. No real surprise, I suppose. Then, many years later, Sean Olive did his subjective/objective correlation study, and it revealed that bass extension and quality accounted for about 30% of the overall sound quality rating. These evaluations were of loudspeaker sound quality performance, and were therefore done in mono - no spatial component was in the source material.
Small rooms have resonances that modify bass sound quality in ways that are not subtle, and if one wishes to share the audio experience, as in home theater, the seat-to-seat variations experienced in the standing-wave patterns are a major problem. Equalization definitely helps because prominent standing waves behave as minimum-phase phenomena, but it cannot satisfy more than one listener with any certainty. Bass management became part of multichannel sound, which aided our ability to address the resonance/standing wave problem. The realization that multiple subwoofers could be used to manipulate standing waves in predictable ways was a powerful tool in attenuating both the seat-to-seat variations and the resonance problems because EQ then benefitted multiple listeners. This was progress on the sound quality front, but envelopment was not considered.
But, there were voices saying that "stereo bass" was lost, which is true. The next question is "how important is stereo bass?". Within Harman, David Griesinger was an advocate, arguing, correctly, that in concert halls the dimensions allow for "directionality" in long-wavelength, low-frequency sounds and that this could/would/might be a factor in perceived envelopment. The long wavelengths (20 ft/6 m at 50 Hz) compared to the spacing of the ears means that the effect is likely to be subtle compared to binaural effects at higher frequencies, but human hearing is good at detecting subtleties. We mounted a demonstration, set up by David, in which we listened to a variety of stereo vs mono subwoofer comparisons using a wide variety of music and digitally contrived signals that should have been good at revealing differences. This was done at several stereo-to-mono crossover frequencies, using different layouts, with the auditioning being done in a largish living room. It was definitely a serious effort.
Differences were heard, but they were quite subtle. Differences in sound quality were expected, because the excitation of room modes is quite different when two subs are operating in mono or stereo - i.e. receiving the same or different signals. These differences would depend on the stereo separation at bass frequencies in the program material (LPs don't qualify - all low bass is mono). But here we were making an effort to focus on differences in "space/ envelopment", to the extent that such a perceptual differentiation is possible. The differences we could report seemed to fade to insignificance at a crossover frequency of about 80 Hz, a figure supported by other investigations described in Section 8.4 of the 3rd edition, provocatively entitled " Stereo Bass: little ado about even less", with apologies to William Shakespeare, if indeed he wrote the words. The conclusion was that the necessary spatial information exists at frequencies above about 80 Hz, and therefore it is present in bass managed systems. It is a stereo "upper-bass" effect, not a stereo low-bass effect. There is also a subtle problem in A vs B comparisons - hearing a "difference" is not declaring superiority of one option - here we were content to hear a difference.
Is that a definitive statement? Probably not, but it strongly suggests that whatever potential there is for enhancing envelopment by capturing directional bass cues in large spaces and reproducing them in small rooms must be achieved while at the same time reducing seat-to-seat variations and room resonances, both of which are easily audible. Because listening rooms are not standardized any wavefront reconstruction exercise is clearly a custom listening room, multichannel audio system - expensive - solution. Present indications in the audio industry are that it is not likely to be commercially successful. But it is an interesting academic exercise.
Recordings, including classical recordings, are mixed and mastered in recording control and mastering (small) rooms, in an industry that seems proudly to ignore science and lacks even basic standardization. It seems to me that there is a "circle of confusion" problem to be added to the list of challenges facing listener satisfaction.
you can not really document an acoustic event as a human mind hears the same event . Great production with the tools of the trade makes enjoyable ”fakes” that apear realistic over speakers, that’s also awesome that it actually works reasonably well.
