What causes the loud shudder sound?

[Blu-Dog]

Originally Posted by Bradapalooza

It's also called bottoming out. So don't become confused when you read something about that

Actually, when you "bottom out", you hyperextend the driver from too much power. The pole inside the coil is slamming back and forth from being overdriven - smoke, bad smells, panic, and expensive replacements usually follow.

You'll hear this zzzzwwwwooooopppHISSSsssscrackle and then this god-awful stench.

That's bottoming out. Also applies to your wallet after this happens.