Sometimes mono sound or monaural can simply refer to a merged pair of stereo channels - also known as "collapsed stereo" or "folded-down stereo". Over time some devices have used mono sound amplification circuitry with two or more speakers since it can cut the cost of the hardware. Some consumer electronics with stereo RCA outputs have a microswitch in the red RCA output (i.e., the right stereo channel) that disables merging of stereo sound into the white (left stereo channel) RCA output. Common devices with this are VCRs, DVD/Blu-ray players, information appliances, set-top boxes, and the like. Video game consoles sometimes have male RCA ends of cables with a proprietary multi-A/V plug on the other end, which prevents automatic stereo merging unless adapters are used.
Disadvantages of merged stereo involve phase cancellations that may have the effect of muffling the final sound output. If channels are merged after being sent through a power amplifier but before being connected to a loudspeaker, it places more stress on the loudspeaker. It has usually been the practice in recording studios to make separate mixes for mono recordings (rather than folded-down stereo-to-mono), so that the final mono master will avoid the pitfalls of collapsed stereo. In video games, merging stereo to mono sound prevents player from discerning what direction distant SFX are coming from, and reverse stereo has a similar setback too. Having an array of loudspeakers connected to their own amplifier outputs can mitigate issues with the electrical load for a single loudspeaker coil and allow the listener to perceive an "image" of sound in the free space between the speakers.