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.

Most stereo and home theater receivers/amplifiers have a Speaker A and Speaker B switch located somewhere on the front panel. Some might wonder what the second switch is for, or how it can be useful. Speaker A is typically used for the primary speakers, such as ones that might pair for television or video.With a little planning and effort, speakers assigned to the Speaker B switch can be used to play audio in another room, entertain a patio area or backyard, or compare two different speakers all together.

Taking advantage of this built-in feature requires running speaker wires from the receiver to the desired room/zone and connecting a second pair of speakers. Most receivers are designed to be able to safely power both sets of speakers (speakers set to both A and B) at the same time without any problem. But be sure to refer to the product specifications first (the owner’s manual is a good reference to check), since there are some receivers/amplifiers that permit only one pair of speakers to operate at any given time.

Adding speakers to the Speaker B switch can make it easier to compare and contrast the performance between two sets. Given that the rest of the equipment is typically shared (e.g. audio source, receiver/amplifier, and even the playing space), one can better zero in on and evaluate aspects of quality. It’s also possible to use both sets of stereo speakers, given different listening situations.It is also possible to use the Speaker B switch to power more than one additional pair of speakers.