How do I tune my amp to my sub?

the manual that came with you sub should tell you waht to tune your low pass fillter at. I know thi is the "pro" way to do it but I set the volume on the dck 3/4 of the way up and the gain on the amp all the way down. play 2 or 3 songs and slowy turn up the gain on the amp if you rewach 3/4 of the full gain with out distorion stop. If you have distiorn piror stop and back the gain off. use the same 3 songs as a test. set your gain whene you haveno distiorn. your sub manuale also will give you a port diminons L and W. also qubic feet of air space. dont forget when add qubic air space to subtract the port size