By connecting one sound system's sound feed into a second system, home-audio junkies can hear two separate audio feeds coming through a single set of speakers at the same time. Connecting two sound systems at home requires that at least one of the devices has an "Output" jack and that the second sound system has an "Input" jack. Most home sound systems fortunately do have these jacks.
Locate the "Output" jack for the first sound system. Sometimes, it is in the front of the sound system; sometimes, it is in the back. It will be labeled either "Output," "Headphones" or something like that.
Locate the "Input" or "Mic" jack for the second sound system. This will be located on either side of the unit, just like the "Output" jack.
Plug one end of an audio cable into the "Output" jack coming from the first sound system. Then plug the other end of the audio cable into the "Input" or "Mic" jack on the second sound system.
Turn on both sound systems and play the first sound system into the second sound system. Depending on the sound system model in use, you might have to set the second sound system's "Audio Input" to "Auxiliary" or "Line In" to enable the first sound system to come through the second sound system.
Adjust the volume and EQ settings, if applicable, on the first sound system to a moderate setting. Setting the volume or EQ too high can result in poor sound quality coming through the second sound system.