You know those things in front of mics to tame the "plosives" ("p" sounds, "b" sounds, etc.)? They look like mesh stretched across a frame, they're everywhere in studios now, you can even make them at home by stretching a stocking across a coat hangar frame. Here's a reference to them ... http://www.soundonsound.com/sos/may05/articles/popshields.htm
It seems by the pics that they didn't start using them until a few years into their Studio Two experience. One of many examples, check out at 3:12 into this video, singing into the Neumann Mic ( http://www.hestudiotechnik.de/image/microfones/2008/u47neumann.jpg
) without a pop shield:
They start showing up in pics within a year or so. I guess maybe people didn't know they "needed" to use them back then?
But my real question is - I wonder why those earliest vocals sounded so good WITHOUT pop shields ... no horrible plosives (Please Please Me, for example, not PPPlease PPPlease Me). Could say maybe the mics were so good (those Neumann's are like gold!) they didn't need pop shields, but if that were the case, they wouldn't have started appearing in the photos in the next year or so.