So my little brother has a Marshall combo from the 80's. The thing is that it has a rather bad sound coming from the speaker, but if you run the line out to another amp, it has a perfect marshall sound. Now, I looked in the back and have noticed that the black wire(negative i assume) is soldered to the positive point on the speaker, and the red to the negative. It also looks like fairly dodgy soldering which leads me to believe that someone has replaced the speaker.

So, does it really matter what way the wires are on, because it has a good celestion speaker in it but it sounds bad unless through another amp. Any help would be appreciated.
it won't damage the speaker one bit. It should defienetly improve the sound and whoever solderer the wires that way, go and slap em'.
Yeah, he bought it from cash converters, and its over 20 years old. Very good reliability and it was made in England. Can't say much about new marshall (MG's and such)