how do I set this dial?
 

I have a soundstream TA1.1000D amplifier and there is a dial labeled frequency range, I have no idea what this dial does or how to use it and have had no luck searching on google, can someone please tell me what this dial does?

I dont mean the lpf or subsonic filter either this is a completly different dial.

It's a high pass filter, leave it at the bottom

There's a subsonic filter right next to it on the amp, I thought subsonic filter and high pass filter were the same thing? Why would I have two?

They are not the same, a subsonic filter stops the low low notes from damaging your subwoofer, only needed for ported boxes though. A high pass filter filters any frequencies that are lower then where you have it set. Still trying to figure out why you even have a high pass filter