I seem to recall that the specs for the Radio Shack SPL meters say they are accurate to 1 or 2 dB (even though they may read in finer gradations). That should make you think twice about using them for level matching. They simply aren't designed for that use. Wrong tool for the job.
Seems to me Sean's got the right approach: level-match with a voltmeter somewhere earlier in the chain. Gain will be the same for all sources from that point on, so you can safely assume that what you're actually hearing is matched.
Seems to me Sean's got the right approach: level-match with a voltmeter somewhere earlier in the chain. Gain will be the same for all sources from that point on, so you can safely assume that what you're actually hearing is matched.