Has anyone got experience of cheap and cheerful sound level meters?
How accurate are they?
More importantly, not worrying too much about absolute accuracy, how consistent are they across frequencies and time - are they good enough to make comparative plots of a few amps/speakers matched with a signal generator and RMS voltmeter on the output*?
*I know that differences in speaker impedance may well be enough to make even such comparisons less than accurate, I suppose I could measure RMS current as well, at least for external cabs.