[4doorYooper]

Does anyone know what would cause a brand new sub to constantly pulsate (makes a "wump wump wump wump" sound, with 2-3 wumps per second, and the cone is traveling at least an inch outward)? The only things that will stop it are WOT acceleration from a dead start, and some times cranking the volume. It's a Rockford Fosgate 10" Punch running off of a brand new kenwood head unit, fully new wiring kit (RCAs with a 8 gauge hot lead off of the battery), and an older but reliable amp. I'm posting because I did the install in a friend's jeep and feel bad that it isn't right. I've done about 6 stereo system installs, but this problem is over my head. Any ideas? If you need more specifics, let me know...

 

[4doorYooper]

Is the sub going to full extension independent of the volume?

Yes, the sub is hitting full extension with little-to-no volume, on occasion drastic increases in volume will suppress the "wump" sound, but is most likely just being drowned out by the other components. He has lanzar tweeters, front doors (5 1/4s?), and kenwood rear cargo area speakers (6 1/2s?) running off of the stock wiring from the Kenwood deck. The only thing running off of the amp is the sub- bridged. We checked the speaker wires, no touching, no bare spots. I think you may be onto something with an internal ground in the amp. The odd thing is that after the initial installation, there wasn't a problem. He was running an old 10" punch, blew it, and when he replaced it with the new sub, the problem started.

 

[4doorYooper]

check the ground and rca's.
unplug the rcas from the amp and see if it continues

We did that once already, but I can't remember if it stopped or not. I think it did, but I'll have him do it again tomorrow just to be sure. I just remembered that I have an old Kicker amp in a closet, so I'll try swapping out to see if the problem is something in the guts of his amp. I'll keep you guys posted, and thanks for the suggestions.

 

[4doorYooper]

Unplugging the RCAs stopped the pulsating.

Gain is set just above the halfway point.

What does that tell us? I'm on my way over there now with the extra amp, maybe I'll have some answers in the next couple of hours.

 

[4doorYooper]

Sorry, I updated Steg about this a few weeks back. It was an internal short in the amp that we were using. I threw in another amp that I had laying around and the problem was solved.

With your problem it sounds like a power supply issue to the amp. Check your amp power supply wire, ground, and your HU Remote wire for nicks/abrasions and check the connections for oxidation. I had a problem similar to this in my truck a few years back, it was a faulty amp ground.