i have a sub with a frequency response from 20-200Hz, and a amp with a built-in Variable 40-400 Hz Low-Pass or High-Pass Crossover . So what should i set the crossover at? high or low and what number?
80 hz low pass is a good place to start. It kinda depends on what you're runnin for mids and highs and where(or if) they are crossed over. Anything above around 80 Hz starts becoming directional, i.e. you start to notice where the bass is coming from.