Originally Posted by Tolstoi
This is an important comment. It is better to adjust the noise level before running the ARC you will significantly reduce the number of measure rejection. Using a sound meter set the noise level of the Anthem so that the noise level at your seating position is around 75db. You need to perform that measurement only once and than remember the value (in my case it is 12db) and use that value before stating any measurement session.
Another thing that's useful prior to running ARC is to set up any internal volume control in your subwoofer (or any other speaker with an internal amplifier) properly.
In Setup / Level Calibration, set the Noise Level to produce around 75dB from the LF speaker, measured with your trusty Radio Shack SPL meter at your dead center listening position (ARC mic position #1). Then adjust the internal volume control of your subwoofer so that its test tone (from Setup / Level Calibration) is also producing around 75dB when its level setting in the Setup / Level Calibration menu is around 0dB. There is no need to be precise in these settings. A ball park setup is fine.
Then run ARC. ARC will determine the proper, and precise, level trim adjustments for each speaker, but the range of the trim adjustments is limited to +/- 10dB. So by adjusting the subwoofer's internal volume control as described, prior to doing the ARC measurements, you make sure that it can be level trimmed by ARC within that limit.
If your main speakers have different efficiencies (more or less volume produced given the same audio input voltage), then it also doesn't hurt to do a quick check with your SPL meter of ALL the level trims prior to running ARC just to make sure you can get all of your speakers to roughly the same SPL level (e.g., 75dB) within the limits of the available level trim controls. There's no need to be precise in this test. You are just making sure that all speakers are within the range that the level adjustment control can handle BEFORE you run ARC. ARC will replace any of these test level settings with the correct level settings when you Upload the ARC results.
Then after Uploading ARC results, go into Setup / Level Calibration and double-check the speaker level settings ARC settled on. Make sure that none of them are pegged at the limit (+/- 10dB). If any are, think about whether you can get the speakers more in balance by adjusting the internal volume settings of any powered speakers, and then run the ARC measurements again.