Omni-directional is a feedback nightmare. I could not use a Shure live with my speakers even on the floor! I suppose if you're technical enough to get the gain, etc correct, you might be OK, but it is not an easy task.
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Yamaha 920 / Yamaha Stagepas 100 BTRs / Senn e935 - LIVE
Roland RD 2000 / Tascam DP24sd / ATEM switcher - STUDIO