Please don’t laugh at this, but I’m very new to this calibrating thing. I just purchased a SPL meter from Radio Shack. Could someone take the time to explain a couple of things such as what the heck is “Reference Level”? Where do I purchase the Avia test disc? (Radio Shack didn’t have it). I already feel like my system sounds great, however, from reading several posts here, it should be calibrated. Also, will this meter only measure SPL? Thanks for any help and/or tips you can give me.