A friend of mine that doesn't have an internet connection at the moment wanted me to as this question.

He has a US Amps 1000W amp, and 2 subs. He seems to have a problem where nothing will come through to the subs until it hits a certain volume level. Then the subs will start to produce sound. If he turns it down past the point where it would finally kick in, the subs stop working again.

I really don't know much about this stuff and i am sorry for the lack of details, but this is what he told me. Sound comes through all the other speakers fine at all volume levels, but not the subs, they only start working at certain levels. He has an aftermarket deck as well.

What are the different things he could check to see why this is happening?

 

check the gain

 

check the subsonic filter...