(darn how do i put line breaks here?) I spent a good deal of time trying to get measurements using the Aperion spl meter but realised that the meter was giving ambiguous readings. For example if I set the the dial to say 60 and get a reading of 64, then change the dial to 70 then i would get a reading of 73 ! Similarly i was getting strange in coherrent readings for many different dial settings ... even at 70, 80 and 90db settings. Finally i bought the radioshack digital spl meter... and that really gave some rock solid readings. I also found the Avia's calibration disk frustrating for audio purposes. It is great for video but impossible for getting a frequency response plot from speakers. the frequency sweep is so quick that it is impossible to take a reading for any given frequency value. Finally ended up using the Rives audio test CD 2, which orgainzes the frequency samples as independent tracks that you can forward/rewind/loop and easily take measurements. Also since I didnt have the correction tables for aperion spl meter ... I could not say many times if the speakers+room were at fault or the meter. The Rives CD had additional frequency samples compensated for the radioshack meter and that was really cool. i was able to get the readings from 20Hz to 20khz in under 15mins.