Purely out of curiosity, I put a low-frequency sweep through the Q950T yesterday from inaudible lows at 10 Hz to about 45 Hz. I only used vol=17 with this test (approximately TV viewing level) to see were the sub would start audibly working clearly. The test started at 10 Hz, rising slowly from there, with the frequency displayed. I could also slow it down, or speed it up with VLC. (I used the settings previously as given in Steve Wither's Review thread, on Friday, 11th Sept for the test.
I could just perceive sub noise beginning at 21 Hz (weak), could feel it clearly at 24 Hz, it was impressive from 28 Hz to 50 Hz. There was a slight rise until about 33 Hz, but I think this was just a result of the gain cutting at 25Hz and 40Hz, thus 32.5Hz being where it would be cut least. I ended the test at 45 Hz.
Above 45Hz is really low-mids, and quickly become affected by the bar and especially the rears which are pretty strong in the low-mids. This is why I wound them back by almost 12.95 dB at 63Hz (and this is with the Bass at -6).
The audible sub response at 24 Hz was surprising given the 6.9 dB cut at 25Hz. You'd think it would be tailing off fast below 28 Hz, but drops off more gradually. A 31-band EQ fine-tune could produce smooth lows to 24 Hz with the Q950T.
In my limited experience of new compact subs an 8-inch with a 24 Hz range when tuned which doesn’t seem to get stressed, nor even warm up, is an eye-opener. I don’t know how loud the system would go making 24 Hz, but I'm fairly confident it'll be considerably louder than I'll ever need.
In reality I'll be using a 31-band EQ to smooth it very slightly, but mostly to attenuate the gain sooner below 30 Hz, to spare my neighbors from low tones resonating their residence. Doing that is too indulgent. So Q950T's sub is delivering slightly more low end than I want. A below 32 Hz bypass button would be a nice option on such a sub, especially given it doesn't have a mute function anywhere (which is an appalling oversight by Samsung, as -12 does not cut it with a sub making 28Hz late at night, I'm left with no option but to manually turn the power off to the sub every night! This, and broken EQ memory, is almost a sufficient reason to return it to the store for a refund.
As for system level volume changes of 0 to +/-6 on the Q950T setup menus, it looks like each of those steps occurs in 1 dB increments. To put this in perspective, a gain change from 0 to +6 will produce a volume increase of 200%. So if you set the Rear speakers to +6, and the Bar speakers to -6, the relative volume change, front to rear, is 398%. That's how far the factory default speaker gain leveling balance was out, from front to rear of the surround image.
If that was my product I'd require that fixed inside of 24 hrs, or heads will roll.