"...The second is the number of subs..."
It’s the number of discrete LFE channels, see below.
I had to think about this (ouch). I think the point one, point two etc., is used in home theater systems with a LFE outputs. A limited frequency band output from the AVR. One point for each channel of LFE. On the other hand in two channel systems with a pair of subwoofers they are really just a separate driver and another "way" of a loudspeaker system. A way being a frequency band of operation. My woofer towers for example can operate outside the band provided by a LFE output. So that system is 2.0 even though the woofers are a separate enclosure. If that system ran pure subs from LFE outputs, it would be 2.2. A least that is the way I see it.
An additional thought; The number of subwoofers does not keep adding additional numbers, it would be the number of LFE channels. One, two, or ten subwoofers run off the same channel is still just point one, same as a single sub with multiple drivers.
It’s the number of discrete LFE channels, see below.
I had to think about this (ouch). I think the point one, point two etc., is used in home theater systems with a LFE outputs. A limited frequency band output from the AVR. One point for each channel of LFE. On the other hand in two channel systems with a pair of subwoofers they are really just a separate driver and another "way" of a loudspeaker system. A way being a frequency band of operation. My woofer towers for example can operate outside the band provided by a LFE output. So that system is 2.0 even though the woofers are a separate enclosure. If that system ran pure subs from LFE outputs, it would be 2.2. A least that is the way I see it.
An additional thought; The number of subwoofers does not keep adding additional numbers, it would be the number of LFE channels. One, two, or ten subwoofers run off the same channel is still just point one, same as a single sub with multiple drivers.