A forum member has just alerted me to this discussion, and my name is being circulated, so I have decided to add some clarification. The topic of sound quality is of fundamental importance, and stereo soundstage and imaging are undeniably key factors in our entertainment. However, the factors affecting all of these perceptual dimensions interact with each other, sometimes in destructive ways. Adding enormous complications is the fact that much of what matters to all factors, especially soundstage and imaging is determined by recordings. Stereo is a directionally and spatially deprived format, and since its inception listeners have sought to "fill in the blanks" with imaginative loudspeaker designs, electronic processing, and audio jewelry of various kinds. There is no "hardware" solution, no "perfect" loudspeaker or wire or amplifier that will suddenly bring "reality" to the listening room. But, audio forum activity indicates no end of trying. In this context, the notion of evaluating loudspeakers in mono sounds ludicrous - or is it?
The manuscript of the 4th edition of my book is now with the publisher, anticipating publication around September. In it this subject is, I would like to think, exhaustively examined and explained, using scientific evidence. Long story short, human listeners are increasingly less sensitive to sound quality degradations in loudspeakers as the channel count is increased from one to two and two to five. The overall result of adding channels is more spatial and directional information, which can be highly entertaining, but the end result is that the binaural hearing system has difficulty separating the spatial cues in the recordings, from the spatial cues in the listening room. Increasing channel count increases the persuasion of the recorded space. As a result listeners are unable to discern timbral errors caused by resonances in loudspeakers with the same sensitivity as in mono/single-loudspeaker comparisons.
The reality is that most stereo and multichannel recordings include isolated, hard-panned, sound images providing instances when the true character of the loudspeakers can be heard. In simple stereo recordings instruments often appear in left and right loudspeakers - mono. All phantom images are double mono. This explains why loudspeakers that win monophonic comparison tests always win stereo and multichannel tests, The reverse is not always true. So, to determine how good your loudspeakers are, do comparison listening tests in mono. Then, if they are good, impress your friends in stereo and multichannel - but choose the recordings carefully: they are a major determinant of what is heard.
Here is something I wrote a couple of years ago - it is long but still not the complete story, as it is currently understood.
