Need help with Amp and Sub woofer set up?

[JSantiago]

Hello everyone! 

So I have a "home theater in a box" amp that is 5.1 surround and is only 100 watts (weak. I know. But that is all i need for my size room.) I also have an 80 watt powered sub woofer that is just laying around. I want to use this sub woofer with my amp I currently have. The problem is, the sub woofer takes a cable that looks like an RCA jack ( i forget what it is actually called.) and the amp only has a regular speaker wire set up. So I just spliced a Yellow RCA cable and hooked up the positive and negative wires and so far it works perfectly! 

But I'm wondering if in the long run this is a bad idea. I mean the entire amp is only rated 100 watts and I'm plugging an 80 watt amp into it. I'm also splicing a wire. So I'm wondering, should I be worried about this set up at all? What should be changed? Thanks for any help!

[JSModerator]

You should get a speaker level to line level adapter for this. The best way to do it is with a transformer but it can also be done with a resistor network. Answer

[SantiagoManager]

You say your HTiB is 5.1 so that means it should have a subwoofer output but the problem is that it's a speaker level output