Why is everyone getting their panties in a bunch?
The guy set up two microphones, inspired by a Beatles movie. It was explained that the Beatles were not really recording vocals with two microphones. We all agree - no problem.
But, as pointed out, there is nothing wrong with being inspired to experiment. Inspiration can come from many sources - you could see a flock of Canada Geese in formation and say: "Gee, what if I set up my drum mics in an inverted arrowhead formation?"
Now, one could argue that the flock of geese was not trying to record music, or even that geese wouldn't recognize music if they heard it. And one would be right. But that still leaves the issue of why setting up your microphones in the shape of a flock works or doesn't work.
So now we discussed that. Clearly, the obvious reason for comb-filtered band limited kind of sound is phase cancellation. And there is an easy test - simply record each mic to it's own track, and mute one of them. If the sound regains it's natural full-spectrum, then we have shown there is cancellation going on. After all, we also all agree that a working 57 and/or a Groove Tubes mic shouldn't sound like that normally.
If not, then we have to look and see if something is broken in the recording chain - a bad cable, blown out mic, overdriven preamp, miswired patchbay, etc. That's fairly easy to isolate - just start bypassing or swapping out each component.
There... wasn't that easy? And no one had to go home with a bloody lip.
