“An A/B Sound System is a type of Sound reinforcement system or Public address system. Unlike a more typical sound reinforcement system, an A/B Sound System provides two electrically isolated signal paths from microphone to speaker, resulting in a system where signals from two microphones only interact acoustically and never interact electronically. This is accomplished by placing two separate loudspeakers at each speaker position and feeding the two speakers separate signals from separate microphones. The purported benefit of such a system is a reduction in phase cancellation and intermodulation distortion, and an improvement in speech intelligibility when two microphones are used simultaneously. A/B Sound Systems are unusual because they require double the speakers and therefore have double the cost.”
The first time I ever heard an A/B system was on Disney’s first touring production of Lion King @ Bass Hall in Fort Worth. During the sound check and went to the farthest balcony to listen and was amazed that I could understand every syllable. When two actors were speaking, each one’s voice was routed to a different set of speakers covering the same zones. I spoke with the audio engineer at the time and learned that the choir was coming from a different PA and the orchestra from another.
Speaking of Lion King, the Broadway show as designed by industry heavy Tony Meola. Here is a Meyer interview with the man himself from 2002.
Meyer Sound – Interview with sound designer Tony Meola
Here is a run gear rundown and interview with Tony regarding the rig itself.
Meyer Sound – The Lion King on Broadway