One of the largest churches in my area is using a pair of Bose L1...not sure what they use for a mixer, but I understand it is an exceptionally efficient and great sounding system.

No feedback issues, and superb sound distribution.

Ian
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Yamaha Tyros4, Yamaha MS-60S Powered Monitors(2), Yamaha CS-01, Yamaha TQ-5, Yamaha PSR-S775.