So i just bought new strings.. and already the first string sounded really really bad it's like a muted sound.. you know that icky disgusting sound.. I didn't either bother to put on the other strings so..
I made a little preview of it..
Sounds like complete shit!
It's not my only guitar that sounds like that.. I thought it was the strings but i bought better quality strings now

You need to check what tension you are allowed to put on your guitar, for example i have a martin guitar that only sounds good with extra light. if i use high tension it sounds "muffled". I don't know if that applies to classical guitars, but why not.
Martin D18.