Most recommendations I've seen are around 18" minimum. Try them at that distance and gradually move them toward the monitor. If you don't see any change in PQ by the time you get them a foot away, you're safe at a foot.
IIRC the dealer I bought my Studios from said 12" is plenty of space. I have a pair of 40s 12" from a CRT - RPTV table top model with no signs of interference.