matengawhat:can you use these to set the volume level of a subwoofer for stereo use and if so how does it work? - sorry never used one!!!
Well yes, provided you can source a test-tone you can run through your system, and then connect the main speakers, take a reading and then disconnect them, hook up the sub and test that. All but the most expensive meters are a little out of whack at low frequencies, but this should be good enough to get pretty close.
If you can't find a test-tone, try running a tuner off-station (of course with interstation muting off) and use the hiss as a source.