75 to 80 dB is your target SPL; you generate a test tone from each speaker and adjust the level so that the SPL readout is 75-80 dB at the primary seating position. For an analog meter, "setting" at 75 means that when the needle is showing 0 dB, the SPL is 75. Typically, the SPL meter has higher accuracy right around the 0 point and decreasing accuracy as the needle moves farther into either side of 0. I don't think it matters for digital meters. Don't forget to set your meter to "C" weighting and "Slow" response. Also, most hand-held meters are not perfectly linear, especially for low frequencies (as are produced by your EP500), and will need to be corrected; so, be sure to look up correction factors established for your particular meter for various frequencies. If you have any other questions, just shoot away. We are here to help.
Thank you for the info.
