Is that how it behaves? Does it just increase the volume of the surrounds and subs? I expected it to match the Fletcher-Munson curves and change volumes for frequencies for al channels.
It also seems to screw up the measurements if you have it ON and OFF during the calibration. Turning it on and off requires a new profile.
There are tons of Youtubers posting things that they don't understand well themselves, this one is a good example. As you probably suspected, he seems to miss the point that DEQ is not about increasing "spl" at lower "volume", but about increasing spl of the
low, and high frequency bands at lower volume bass to some extent on the so called "loudness curve/Fletcher Munson curve", though Audyssey emphasized that theirs are more accurate their the old Fletcher Munson, in various ways.
I happen to have saved some of the original write-ups by Audyssey, from years ago, those articles would be very difficult to find now on the internet. Below is from one of such old articles:
So, that Youtuber missed the point about frequency response versus volume. That's why using his Radio Shack meter the way he did prove nothing! Just read the specs of that meter and you will see the obvious reasons.
In the MultEQ-X user guide, they included a whole page on "Audyssey Recommended Demos". For those who are serious about understanding how DEQ might work for them, should probably try it.
Audyssey DEQ is, like a lot of things, not perfect but it is a little more sophisticated than what a lot of people assume it to be "just" like loudness control, based on Fletcher and Munson's.