I'm relatively new to this stuff and am trying to set my gain with a dmm since I've heard that it is a pretty accurate way to do it. Voltage of the output = sqrt(RMS Power X impedance of the speaker) but am confused because if I am wiring my two 4ohm subs to create a 2 ohm load do i multiply my amp's rms rating by 2 or 4 to find the voltage? Also, does anyone have any advice on how to set subsonic and lpf settings, I know basically at what settings they are supposed to be on but do not know how to accurated set them because my amp only gives numbers for the lowest and highest setting, nothing in between. this is what I mean. http://www.mtx.com/caraudio/products/manualsQuickInstall/amps/XT_600XD_300XD_InstallSheet.pdf
setting the gain with a DMM is a ballpark figure...after the subwoofer is installed into any enclosure there is going to be impedance rise. I usually set the gain by ear and listen for clipping...but it takes practice to set it correctly by ear. Then I double check with the DMM. Subsonic should be off for any sealed enclosures...in ported applications I usually set it 5-10Hz below tuning. Lowpass setting depends on the install and how well your midbass can blend with the substage.
