Large rooms (>4m across) with metal losses, or very large rooms with out metal losses. Room must have fixed seating or well defined areas where users will be.
Divides the area into smaller rectangles giving much more even field strength over the room where there is metal loss, or for large loops.
Between the loop sections there will always be a dead line with zero signal (see graphic). This is completely unacceptable if users might be in this area, hence single arrays are only useful in very specific circumstances. More rectangles means more cable length which requires more voltage headroom in the amplifier which must be checked carefully.