Got a really special gig for three days starting tomorrow. Chamber wind quintet with piano and soprano, their third CD. In our really beautiful hall, I rarely use ambience mics, as I rely on tiny amounts of reverb later to add air and bloom if at all. If ambience omnis were to be used, what is the best practice for locating them, distance-wise from the group and main pair. I assume they should be well into the reverberant region of the hall, ie further than the critical distance, but how much further as a first try? The width of them is another variable I do not have a good intuitive feel for, the width of the group, 1/3, 2/3 positions across the hall? Any hints from you ambience gurus would be welcome. I remember taking note of some live BBC sessions in St John's Smith Square and St James Piccadilly years ago, where AKG414 pairs were out wide, almost near the walls and at the edge of the stage, but only 2m in front of the musicians. This seemed odd to me at the time. But those BBC blokes are pretty saavy when it comes to live recording.