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.
Could be a bad solder or connection at the end connection...You could easily clip of the connector and just use bare wire and if the problem is with the connector you will no longer have the problem..
Some speakers have binding post where the wires tend to get loose at the other end. You connect the speaker cables at one end and the wires at the other end can begin to come off - this happens on My Mirage Ms a few times.
Thanks. I get it that the cable is suspect. In fact its probably exactly the case. My question was has anyone experienced anything like this that was not because of the cable?