[David Spearritt]

Booj, you need to be more enthusiastic with your search buttons. There is so much info on this subject both here on GS and out in many other places.

eg.
Full circle around a Blumlein Pair - a capella - Had a fun recording on Sunday. A vocal group at a college about 90 minutes away hired me to record them for an archival CD for the members. 17 singers - I had them stand in a circle around a Blumlein p

PSW Recording Forums: Klaus Heyne's Mic Lab => The glorious Blumlein

and an excellent article:
http://www.davidgriesinger.com/primer.doc