Subwoofer Out VS Subwoofer Crossover

I'll look closer. I saw some info that said the amp (yamaha 701) crosses the sub at 90hz, I understand crosses. Is this what is called a low pass filter?

And thank you for your response.

Manual states cut off freq at 100. so if i use the sub out, what shall i do with the subs onboard crossover dial/setting? 

Thank you all for chipping in. I never realized how little I know now that I’ve acquired this integrated amp that is a bit more "stout" then anything I’ve ever owned. So my first question was yes, a little lite on info. This stuff is probably beginner level stuff. I’ve always wanted to own a system with a good solid punch. So, I found myself grabbing the yamaha integrated amp, 2 polk speakers, and a powered sub.

The amp is a Yamaha A-S701 (manual). It maintains a single RCA out for the sub. It also maintains an impedance selector.

I’m running 2 Polk Monitor XT70s (manual).

I have a 100W Sony sub with speaker in and outs, as well as a single RCA in, and an adjustable cross over dial.

My thoughts were to remove 80 or so and down from the speakers, and allowing my sub to take care of 80 and under, aprox. My understanding is that this keeps the amp from having to pull a lot of low freq weight. As well as free up the speakers for a bit more volume headroom, in order to play loudly, safely.

I’m also new to the impedance setting. The speakers specs/manual shows they run at 4ohm. I’m not perfectly sure if I’m to set to high or low on the impedance filter. I'll be simply playing 2 speakers out of A.

Thank you again. I’m excited at what appears to be a nice leap up in home audio experience. 2.0 that is.

Interesting. No sub. I'll definable try that.

Any input on the Low or Hi impedance setting per these 4ohm?

After looking at this chart, I'm pretty sure it's LOW.