What do you mean by accurately? Why cant you just use your ears to listen to what sounds best?
Its a subwoofer man, really how hard is it to see what frequency cut off sounds best? Just turn the dial, listen, turn dial again, and repeat until you like the sound. Tune it for what YOU like, unless you are competing then thats a different storyWhen someone does not have either a good set of headphones or a home audio setup, it is hard to know what to listen to...