Hi All,
I love using omnis but find that they only really work well in our application in a flat, open/outdoor space.
Since they are omnidirectional (below about 5kHz), they often deliver a very smooth, natural sound while giving the feeling of being submerged in the music. The high-end directionality does lend value to the notion of actually pointing them at a high-frequency source (at least at the P.A. itself) as opposed to straight forward or totally off-axis. Of course, Tim's results may contradict this. When are you bringing those Botanic Gardens samples. Anxious ears await. : )
As far as low-end rolling off with distance, it is, like all sound going to decay at roughly 6dB per doubling of distance. High-end, however, is much more subject to absorption in air. Further, omnis are not subject to proximity effect (also related to inverse square law--doubling of level per halving of distance). Consequently, the omnis will continue to pick up deep bass from a greater distance but the high-end will be attenuated. As a result, it is very easy to accidently get VERY bass heavy recordings from omnis at a distance.
All said, my Grateful Dead, St. Louis, Riverport 7/6/95 tape--B&K 4006 omnis on the lawn--is one of my favorite recordings that I've ever made. I attribute this in big part to the delays hung from the back of the pavillion that accented the otherwise missing high-end.
On the other hand, my 15th row Neil Young & Crazy Horse '91 McNichols Arena tape (AKG 462's) is among the worst I've ever made.
Omnis are tricky but when they work, they are sweet!!!
Happy Recording Everybody,
Marc