why do my car speakers vibrate, especially when I turn up the volume..do I need better speakers?

Answer 1

All speakers vibrate. That is how they work. Now if you mean they have a buzz or sound distorted then yeah, you probably do need new ones.

Answer 2

All the speakers vibrate, that's how they produce sound, it's like your can feel vibration in your throat when you speak. The more you turn up the volume, the bigger the vibration, and the louder it sound.
But, when it starts to produce nasty cracking / distorting sound when you turn up the volume, maybe it's been broken.
Or, maybe it's just mounting problem. Check all the mounting bolts, if there is any loose, and also check the interior panels, sometimes vibration sound is coming from them.
Or, maybe you turn up the bass to high, regular 6 inch speaker won't handle the low frequency well, it will produce nasty cracking tone instead, and you'll blow them out. For that job you need a subwoofer. Try to turn down the bass and check if the vibration you meant still there.
Or, if the cracking sound doesn't exist when you don't crank the system up, maybe your speakers just don't have big enough power capacity, if that's what happen, then you need to replace them with speakers that have bigger power ratings.
For example if your current speaker is 25W, you should buy a pair of new one that at least 100W.

Answer 3

You have probably busted the speakers. You might need to get some new ones, and if you want to continue turning the volume up, I suggest getting louder, and bigger speakers.

Answer 4

Either you have blown out your speakers or it could be touching something like a wire. If it is blown out you need new ones