I'm trying to find an SPL meter with a frequency response down to at least 20 Hz. The Radio Shack ones, and several other low cost makes I've seen, seem to go down to about 32Hz. This isn't low enough for accurate sub measurement. I found the RS meter calibration table at: http://www.danmarx.org/audioinnovation/rsmeter.html I don't know whether this applies to the current models (the picture looks dated), but it does suggest that at 20 Hz the current models may be more than 7dB out. Behringer make a calibration microphone with a very flat response, which would probably be good for connecting to a PC running some spectrum analyser software, except that it require 'phantom power' - and a suitable supply probably doubles the cost. In fact I think the PC solution would be the ideal running TrueRTA or something similar. Can anyone recommend a) an SPL meter that goes done to 20Hz and has correction factors if necessary), or b) a good PC microphone with a flat response?