I was reading the manual and can you tell me why this is necessary to have -3db trim within the receiver?e) Using the Manual Speaker Setup menu of your receiver or pre/pro, play the speaker level-matching test
tone and adjust each speaker to read 75 dB (“5” on the meter with the range switch set to 70) using the speaker Trim controls found in the menu for each channel. When playing the test tone for the subwoofer, use the VOLUME control on the STA-800D/STA-1000D to raise or lower the level of the subwoofer to read 75 dB leaving the subwoofer Trim control in the AVR or pre/pro set to -3 dB. (Note the meter may fluctuate by several dB when measuring the subwoofer. This is normal and what you are seeing are room modes in play. Use the average of the swings to determine the volume of the subwoofer.)
f) From this point forward to add to or decrease the level of your subwoofer(s), use the subwoofer Trim in
your receiver. In some cases the level of your subwoofer Trim may exceed +/- 5 dB after tweaking your sub level to taste. If this occurs, use your SPL meter and a combination of the subwoofer Trim in your AVR or pre/pro and the VOLUME control on the STA-800D/STA-1000D to get the subwoofer Trim back to -3 dB while reading your desired subwoofer level on the SPL meter.