Well here's the issue. My band and I decided we need a better way to amplify our vocal, as we are currently using an old 15W guitar amp. We found an old mixer, but its meant for DJ'ing and only supports 2 tracks. My drummer has two big old speakers, the kind you use for attaching to a stereo or whatever. If I plugged a mic into the mixer, then ran the output into the speakers with a 1/4" cable, would it work?
Only if you have a powered mixer, the signal from the mixer needs to be amplified before it reaches the speaker. You might be able to drive the speakers with the amp you're presently using if they are efficient enough. You probably won't get a result that is gig worthy, but it ought to get you by for practice for a while.
Your going to have to buy an amp...

Signal chain is like this


Just shop around for a really old 400-500 watt speaker amp. You can probably get one for 100-200 bucks if its just a piece of junk but still works.
Quote by deg0ey
The best pickups for emo are no pickups at all...


1996 Les Paul Classic w/ Alnico II's
Marshall Jubilee 2550
Avatar 2x12..V30 and G12H
Vox V847 Wah
Assorted pedals