Yamaha HS7 monitors hissing

[Dogtag]

Hey guys

So I just bought these Yamaha HS7 monitors to up my production game (my first pair of monitors, ever). I was really excited and couldn't wait to set them up. I decided to hook them up with my phillips spa7380 subwoofer using 3m jack to RCA cables (devine va3013).
So basically:
-When plugged in and turned on they don't hiss at all.
-When connected to my subwoofer, they hiss, even when my woofer's output is at 0 and when I start turning up the volume, at a certain (loud) level they even start making very high screechy noises, I can't really describe it because it scared the hell out of me and haven't gone there since haha. At times it even buzzes (for example when I'm on this site lol)
-The hiss on the left output is worse than the right one (I switched the left and right cables and then the right one hissed more so that's definitely the woofer I guess)

Is it my woofer's fault and should I just connect it straight to my pc? The cables are brand new but could it be that they're unbalanced?

Help me out please.

 

[bandcoach]

I'm guessing a badly designed or badly implemented low pass - high pass filter (aka cross-over) in the sub-woofer - but I need more information from you first....

you have assumed that because you have given us the make and model we either know it will go look up how it likes to be wired up - not true

a link to the manual for the sub would help

 

[Dogtag]

I bought an audio interface and balanced cables, the problem is solved, thanks for the reply anyway!