I'm read the documention several times, and have taken many measurements. I'm using the RS meter, set to C weighting. I get a plausible response curve down to 20 Hz, but then the curve becomes RULER flat down to 2 Hz! That can't be right. Also, when I check the "C weighting" box, the curve rolls upward steeply, as if the program is compensating for a nonexistent C curve. Any help would be greatly appreciated.