Stage speaker placement

Mainly depends on how big your stage, the general angle of the speakers inward about 15 degrees on the line, if two pairs of speakers, then a pair of straight forward, a tilt inward 15 degrees on the line, so that the main soundstage is more uniform, the actors on the stage need to listen to the sound of the words that can only add a pair of return to the speakers, the world has not yet been developed before and after the speakers of the stage speakers, mixing consoles and amplifiers, the most ideal! Position is directly across the stage, because you can hear the direct sound of the speaker system, but small performances there is no need to do so, because of space issues on the side of the stage on the line, so that the actor's state can be observed clearly. The problem of whistling is not so good solution, I do not know whether you have a preamplifier with equalizer or feedback suppressor, if not advise you to add a it! To not add back to send whistling will annoy you want to what the machine and also easy to burn speakers, I do not know the owner is not convenient to tell you what the preamp equipment? I hope that the previous said to help you! Purely personal opinion, for reference only.