It won't work well if you are putting drums and bass through it, probably very honky sounding. And you could blow the guitar cabs, or even the bass cabs if you try to push too much low end through them.
For vocals only it will work. It won't sound very "good" by normal PA standards. Do you want clean, understandable vocals and deep bass? You won't get that. It will probably be kind of a dirty, mid-focused sound which might work well for some kinds of music.