Sub making noise without input

Make another video showing your connections on your amplifier I've hooked this set up before so I can understand partly what your saying, are your filters correct?

need new subs the connection wire to the cone is bad

check all your supply wiring's specially the one that is connected directly to the positive terminal of your battery, it has to be of enough gauge to supply your amplifier's wattage, and it is has to be properly grounded to the body of your car.

yes. A good idea. Kill power to the sub, then unplug and remove everything from the sub. go ahead and plug it in again and check for buzzzz.
That is test one. if you have buzz still, its the sub assembly. bad luck, but not impossible. If the buzz is gone its one of the signals to the sub. They can produce a buzzz without any signal coming from your stereo equipment. Replace the feed line, enjoy! BTW...Kef sure does sound clean. good choice.

A few more questions-
Does the sub hum without anything plugged into it except for power? If it makes a real loud hum almost a squeal then I think the rca cable between the receiver and the sub is dead shorted and needs to be replaced. If it's more of a low level hum, then it's a ground hum caused by many things, ie........the receiver and the sub being on different power circuits in the house.......sometimes diconnecting the cable tv feed as it enters the room while the sub is connected and humming to see if it stops........the easy fix sometimes is using a 3 to 2 prong ac adapter but lifting the ground on such a powerful amp could be a fire hazard.

You may have a ground loop issue. Make sure your ground lead is as short as possible (<1ft, if possible) and that it is mounted to a nice, clean (unpainted) spot on the vehicle. If you have multiple amps, try and ground them to the same point.

blown capacitors. take to a friend or electronics repair that can replace with better capacitors. had same problem with an old comp 1200 amp. friend of mine replaced with better capacitors and wooohh mamma!

1) Make sure a bridged load of no less than 4 ohms is applied.
2) make sure both the left & right channels are working.

check the impedenc on amp and speakers.if speakers have lower ohm the amp cant push them also can cause damage to amp.how do you have everything wired must be specific.high level inputs,rca,.how is the radio and amp wired together,where are you getting power sup[ply from and how?
chriszambrotta@yahoo.com

check for broken rca input GND.