Subwoofer acting wierd

Question

i have a 10 inch 750watt subwoofer and a 600 watt amp in my car and i
played some basstester songs on it and it stopped working today. so i
turned the car off and restarted it and the woofer works but only when
the volume is under 15, i used to play it on 20 and it worked fine. if
i turn it up past 14 the woofer stops working and i have to turn the
car off and restart it. what do you think the problem is? did i blow it?