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.