It works well for me, I use it for late night viewing while the wife is asleep upstairs and the combination of the increased clarity provided by XT32 and the bass attenuation of LFC has dramatically reduced the incidence of complaints from the wife. The truest empirical test!
Previously (Denon 2113 with XT) I had to set the ref level offset at 10 or 15 and Dynamic Volume at Heavy (Midnight) setting and I still got some complaints with bass effects and louder passages. With LFC engaged, combined with the much smoother bass calibration + extra dialogue clarity provided by XT32, I now only use a ref level offset of 5dB and keep Dyn Vol on Medium. It's a better overall solution because there are superior clarity and dynamics overall but I can target the bass directly with LFC as opposed to dulling the overall soundfield by maxing out the ref offset and Dyn Vol levels.
I quoted AustinJerry's measurements of LFC below, you can see there is a significant amount of attenuation in the bass. However, due to whatever "psychoacoustic processing" secret sauce Audyssey does, it certainly doesn't SOUND like there is 20-30dB of bass attenuation.
The strength of the effect really varies based on the "containment amount" setting (varying from 1-7). At the lowest setting (1) it barely feels like the bass is being attenuated, although Jerry's graphs demonstrate that there is actually around 15dB of attenuation at the lower frequencies. Obviously you don't get that "feel it in your body" rumble but that's precisely the stuff that transmits through walls which you are trying to eliminate... overall at the lower containment settings the bass doesn't feel that neutered though. As you crank up the containment, the bass gets more and more anemic, at levels above the default (4) it definitely feels neutered, although not nearly as bad as if you switched the sub off completely for example.
Overall it works as advertised. I definitely wouldn't call it a "gimmick". You can dial in the containment setting that gives you a good balance of preserving bass impact while cutting out the transmission through walls.
Originally Posted by AustinJerry
Measurement is taken from the Sub1 pre-out. LFC requires Audyssey to be engaged
. DEQ and DVol are off, of course. At 20Hz, toggling through LFC values of 1,2,3, and 4 results in a decrease of -15dB, -20dB, -24dB, and -27dB, respectively. Pretty kind to the neighbors, I suspect.