RE the boxy sound -- I've always assumed it refers to those cheap loudspeakers with box colorations. Which is what you get for $650, though cheap dynamics like the Elacs have gotten a lot better in recent years.
Look at the Dynaudio LYD5 or Genelec 8030C recently reviewed here, the price of an LRS with appropriate beefy amp can get you something like this.
People that buy Magnepan speakers are into hi-fi and likely much more serious about their two-channel systems.
They're definitely not into high-fidelity, though. I wonder how many kooky audiophiles you got in their buyer base that bought them just because of the hype, wanting to be part of the "Maggie club", their unique look and finally
maybe their sonic quality on very select material.
The proposition "people having some == they can't sound bad" is preposterous and you should know it.
A couple of issues there. One is that you need the output from both bass panels because they are asymmetrical (as you observed) and the acoustic dipole equalization is designed to interleave (two segments on one side, three on the other). So the bass response won't be smooth if you listen to only one speaker.
The other I think is that with one speaker, you'll miss one of the main reasons people love planar line sources, despite their limitations -- the awesome imaging.
As always, I agree that mono testing is flawed by design.
Why are measurements so poor for a design that has been celebrated for decades as one of the best sounding speakers in the world?
That's a nice opinion. To me it looks more like a vocal minority bolstered by the audiophile and mostly corrupt press also known as the "Can hear the emperor's beautifully musical trumpet" club.
The apparent answer would seem to be that the speakers are fine - the measurements are wrong.
The difference between religion and a scientific theory is that any solid evidence against the theory produces doubt in it while in a religion, the doubt always falls on the evidence.
If the LRS measurements are so misleading, what veracity should be placed on all the OTHER measurements of the "Audio Science Review" website? Again, the answer would seem to be that if the measurements in this "review" are so flawed (or else so misleading), then great caution should be applied when assessing ANY measurements from this site.
Truth hurts?
I suggest you try to read all the research behind these; of course, that's only if you're not one of the expected Magnepan hurt fanboys.