Speaker cable, connection

I was not getting the sound out of my amp and speakers as I expected. The highs were muffled and lost in the background. I disconnected and reconnected the speaker cables several times with no difference until the last time. This last time, I also twisted the cable at the solder joint thinking there may be a poor connection.
The sound came alive as if I just installed new tweeters. I am thinking that its a bad cable/solder joint. I have not reworked the cable because it sounds fine right now. But I wanted to get some feedback from others. Has anyone experienced anything like this? If its not the cable, then there is something going on with the amp.