AVman09, here's what I'd do:
Place the RS SPL meter on a rigid surface, ideally a tripod aiming straight up at about ear height from a seated position. Mark the tripod feet positions on the floor with tape so you can move the setup to another room yet replicate this exact location, if need be, later.
Set it to its most sensitive range (I've only worked with their analog meter, but I assume the digital one works similarly) and turn on A-weighting or C-weighting and leave it set that way for the duration of the test.
Play a steady state tone, a sine wave, of say 120Hz [intentionally a little above the subwoofer's range] in the main room, loudly enough such that the SPL in the adjacent room reads it easily
well above the ambient room noise by at least 10 dB, or preferably even more. [The "neighbors" room, or it could simply be your own adjacent room with the door shut, which I assume would be easier to pull off, although it's not as ideal]. Record the level by writing it down. [Turn off any extraneous noise generators like AC/furnace/refrigerator, fans, DVR hard drives, etc. and shut the windows, obviously.]
Turn on the LFC circuit and record the amount of sound reduction, in dB, as you switch between its (7, did you say?) levels in the far room, while playing the steady tone in the main listening room.Now without changing the master volume control on the receiver
[did you get the x4000, or some other?] measure what amount of sound reduction occurs in the main
listening room, also for the 7 setting levels. You will of course need to reset the scale you are working with on the SPL meter, since now being in the the main room it will probably be off scale otherwise. Mark the tripod feet with tape marks on the floor here too.
You might want to also repeat the entire test but instead using a frequency in the sub's range, say 70 Hz or so, so we can see what it does there too.
This test will show us how much the LFC circuit reduces the level to our neighbors, at its various settings, and how it might be different from us simply lowering the master volume level ourselves, or at least that of the sub signal, if that's what it mostly does.
Thanks for your effort.
P.S. There are various sources online to download sine wave test tones at any frequency you choose, if you don't have them already at hand. Here's an example:
http://www.audiocheck.net/audiofrequencysignalgenerator_sinetone.phpEdited by m. zillch - 5/16/13 at 9:13am