Sub makes fart noise.

Bare with me, don't know a whole lot about audio. My sub sounds like it's going out, but Im not 100% sure. I've had it less than a year. It was working fine then on the freeway I could hear an unusual sound when it hit a certain note. Then it stopped working completely. Maybe a fuse?

Also I hit the breaks about a week ago and it fell off my back seat. Not sure if this has anything to do with it.

Haven't had time to see what frequency it happens at so I don't have any more info than this at the moment.

 

Perhaps as a result of the cone contacting a hard object when it fell off the back seat, there may have been a permanent deformation created either on the cone or the voice coil, and the voice coil might be making contact with the magnet - and momentarily shorting at certain frequency(ies). Once the voice coil warms up, the wire might be expanding enough to remove the contact, and allow it to play for that listening session. The sub can only go through that type of cycle so many times before the voice coil wire snaps and permanently open-circuits, requiring a re-cone service. The amp also doesn't like having its speaker terminals shorted either.

Check the impedance of the sub while the cone is at rest - make sure the impedance matches the ohm rating of the sub (disconnected from amp). Another check would be to remove it from the box, then just push and pull the cone into and away from the frame...it should be very smooth, but if there is any scraping or scratching 'feel', the voice coil is touching the magnet while its playing, and the sub is damaged. Also check the amp's voltage output, and make sure its not a flat DC voltage at without music playing (idle)- this should be tested during a cold start, and also after the amp has been warmed up (speaker can be connected) - if there is any DC voltage output, there is a serious problem in the amp, and its output FETs probably need replaced.