Car Stereos: 2004 Tundra speaker problems, speaker quality, tundra

Question
I have a 2004 Tundra and I'm getting a fluttering sound from the speakers.  It's not like a loose speaker or broken cone sound. I can usually only hear this more in voices than bass or instruments.  Could this be from the factory amp?  Any help would be great!

Answer
Wade,  Most times distortion is caused by speaker quality.  There many things that can happen to a speaker to cause it to make bad sounds.  Normally, an amplifier just reproduces sounds, and the distortion starts with high volumes on the lowest hertz'.  I would definitely be looking at the speakers.  Hope this helps, Scott