Direct answer
The three numbers describe the main listening-layer speakers, subwoofer channel, and overhead or height speakers. A 5.1.4 system therefore uses five listener-level channels, one low-frequency-effects channel, and four height channels; 7.1.4 adds two surround-back channels. The “.1” does not limit the room to one physical subwoofer—multiple subs can reproduce the same low-frequency channel to improve seat-to-seat consistency. The numbers also do not describe speaker quality, placement accuracy, room acoustics, amplification, or calibration, all of which can matter more than adding channels.
Choose the layout after mapping seats, room boundaries, doorways, ceiling construction, and speaker angles. Dolby's official speaker-setup guide illustrates supported layouts and the intended meaning of each channel group.
Sources and technical references
Use the organizations responsible for a product, platform or standard to confirm current specifications and compatibility.
How this answer was prepared
Camelback Smart Homes publishes this FAQ library for homeowners, design professionals, builders and property teams comparing integrated technology. Answers begin with the practical conclusion, then explain the factors that can change it.
Limitations: This is general educational information, not a site-specific design, quote, code determination or compatibility guarantee. Final requirements depend on the property, construction, infrastructure, equipment versions and project goals.