I fully agree with what you say about summarizing the science.
Here's a very brief summary on some relevant research.
First out is a fairly old study that addresses full range correction and even compares with anechoic correction. Measurements and subjective evaluations in and outside the sweet spot were used. This is IMO very high quality research by AES standard.
P. Hatziantoniou, J. Mourjopoulos, and J. Worley, "Subjective Assessments of Real-Time Room Dereverberation and Loudspeaker Equalization," Paper 6461, (2005 May.). doi:
Abstract:
Formal subjective tests of real-time room dereverberation using Complex Smoothing were conducted to assess the robustness and the validity of the method under real sound reproduction conditions. For comparison, anechoic, inverse loudspeaker real-time filtering was also subjected to assessment to decouple improvements due to the complex smoothing inverse room filtering and due to mere equalization of the loudspeakers. Results derived from a multivariate analysis of variance (MANOVA) of the test data, verify the conclusions detected in the past by the objective evaluation of the method e.g. significant improvement in sound quality and immunity to real-time processing artifacts independently of room size and listener position.
Mourjopoulos and colleges had done several papers related to in-room correction and the use of complex smoothing prior to this, and they all pointed in the same direction as the abstract above. This paper strongly indicates that a) in-room correction has merits also high at high frequencies and b) a correction based on sophisticated evaluation/smoothing techique is typically capable of improving sound quality outside the sweet spot as well as in it. As far as I know, the findings remain undisputed. The papers on complex smoothing was important input to the design of Audiolense in the early stages. Complex smoothing was not the end game here, but it was sufficient to disprove your working hypothesis.
And then we have Olive's first paper on room correction. It came a few years later. is less sophisticated, but nevertheless points in the same direction, showing a strong correlation between how it measures in the sweet spot and perceived sound quality .. across the whole frequency range.
S. Olive, J. Jackson, A. Devantier, and D. Hunt, "The Subjective and Objective Evaluation of Room Correction Products," Paper 7960, (2009 October.). doi:
In the proceeding years Sean Olive have done follow-ups on ideal in-room responses and ideal headphone responses, like this one:
S. Olive, T. Welti, and E. McMullin, "Listener Preferences for In-Room Loudspeaker and Headphone Target Responses," Paper 8994, (2013 October.). doi:
In this paper, even with close-to-perfect designed speaker, sweet-spot based correction is required to approach the ideal response in a frequency region where you guys question the merit of in-room correction.
As it happens, my personal preference is very much aligned with these research findings. I only prefer an even straighter target than the one found by Olive et al. But there are many who prefers something similar to the "Harman curve", with a varying degree of lift in the bass. And you may prefer the sound of a partial correction that does very little above Schroeder and possibly preserves more of the speakers' original character. Audiolense gives you the freedom of choice.
