Can you use a stereo speaker for a guitar amp?
Yep. It was not designed as an instrument speaker and will likely be killed. It is also probably pretty quiet as stereo speakers usually have a much lower sensitivity. Exceptions are JBL, Altec, EV and Klipsch which used very high quality speakers that were nearly indestructible.
Can you use any speakers for guitar?
Playing Guitar With Speakers
Or maybe you have a great stereo or surround sound system and want to make use of those speakers instead of buying a guitar amp. The good news is that you can use any speaker system you want to play electric guitar.