I often see posters saying that they listen at "nn" db's when they watch DVD's. How can I figure that out? Using AVIA and a RS SPL meter, I have already calibrated each of my speakers to 85 db. When I did this my "master volume knob" on the receiver was at -6. But when I watch a DVD, I am comfortable when the "master volume knob" is at -15. So how do I figure what db level -15 is? I can go back into AVIA and see how many db's my right front speaker puts out at when the "master volume knob" is at -15. But would that be accurate? Wouldn't the cumulative total from all the speakers be higher than just the one speaker? thanks.