Originally Posted by vodil
That is certainly not true. There are AVRs that do have 2 independent sub-out channels and use the ".2" designations. Furthermore, Audessy can adjust them independently--which is not easy to do by yourself. ARC could not do that.
Well, we have to distinguish between hardware, software and layout designations. The 5.1 and 7.1 designations originally specified the number of discrete channels encoded in the source. Since LFE was always mono, there really is no such thing as 7.2 from the software perspective. You may have had multiple subs, but they were all fed from a mono signal (although potentially each sub was subject to different delays, levels or EQ profiles applied to them behind the source material).
And of course, that is what some AVRs do with two sub pre-outs. They can adjust delays and levels for each sub pre-out independently, and manufacturers may use the 5.2 or 7.2 designation to communicate this capability to the market. But this is a hardware implementation. The hardware may be 7.2 but the source is still 7.1.
And then some have taken to using the 7.1 designation to express the number of sub units in their system. They may say that they have a 7.6 system if they're using six subs.
And now, even Dolby has confused this nomenclature by using it to express the number of speakers in an Atmos system, even though each speaker is not a channel in the mix anymore. For example, one could have a 9.1.4 Atmos home system. But there are still only 7.1 channels in the software, with the rest of the speakers playing sound objects that are not assigned to a particular speaker channel but a location. The Atmos renderer decides what sounds go where based on your layout. IOW, there is also no such thing as a 7.1.4 mix or a 5.1.2 mix. The nomenclature no longer refers to just software.
So the waters have been very muddied over the years in this regard. DS21 started this conversation by replying to someone asking about whether the MRX were 7.2.4 or not, saying that 7.2.4 is not a thing. He didn't specify what he meant, but I knew what he meant and in the context he was thinking, he is correct. Of course, he could have read between the lines to see what the poster meant and been a little more helpful. That's what I tried to do with my post.
Can the levels be independently adjusted for the two subs like Marantz/Denon has allowed for years or is it truly an internal Y-connector?
No, I don't believe they can. Pretty sure it is just an internal Y-connector.
Does ARC2 do any better than ARC1 on subs?
I'm not familiar with the changes made to the algorithms between the two versions, but I bet Nick@Anthem knows a thing or two about it.