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General audio question; "pulsing" subwoofer?

26324 Views 16 Replies 8 Participants Last post by  IkeRay
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...
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Is the sub going to full extension independent of the volume?

You likely have a problem between the sub and the amp. Take a close look at the speaker wires and make sure the positive and negative wires aren't touching anywhere, particularly at the amp connections.

There are other things that can do it, such as an internal ground in the amp causing AC output or other issues.

If you can let me know what other pieces are hooked up to the system I can offer some troubleshooting ideas.
G Rahn said:
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.
check the ground and rca's.
unplug the rcas from the amp and see if it continues
smartjay28 said:
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.
How did the subwoofer before blew? The amp must have problem (possibly clipping) to cause the sub to blow if it didn't do that previously. When an amp clip, it can send more power to the subwoofer, which in turns, the heat from that extra power can blow the voice coil of the sub.

Swap the amp and see if the problem exist. If the problem is gone, then the old amp is probably broken. If it still doesn't fix the problem, then the problem lies within the wiring of the speaker. That pulsing action seems like the amp is clipping and clipping would mean overdriving the amp. That would cause the subwoofer to excurt out a lot.
This problem sounds very familiar

i think the same thing was happening to someone's sub, my friend installed. Since i didn't do the install myself, i couldn't really tell you how everything was run. but if i remember correctly the sub blew after like 15 min of troubleshooting, and i dont' think we ever resolved the problem. but i'll try and remember if we did figure it out (but it was probably a good 4 or 5 years ago)

if you believe the first sub blew from similar problems, then it is probably a problem with the amp (clipping as GSteg stated).
but since you said it only started with the new sub, i'm thinking it might be a defective sub? (which doesn't make much sense in my mind, but you never know)

i would just try single out the problem. try using a different sub, to see if the problem remains, try using a different amp, and see if that is the problem. and even try maybe using a portable cd player or something, and get the RCA signal from a different source.
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.
The problem might be the amp when it gets signal.

Let us know how it goes with the new amp.
i have the same problem, but its like every 3 seconds i get a "womp". i think it is something between the amp and the hu because the amp has the red light go on every 2 seconds then it does the "womp" then it goes green and slowly fades to red again..... didn't have the problem until i got the new HU (pioneer DEH-16; previous HU Durabrand: walmart)....
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.
don't laugh but i had the same problem...except it was the driver front bose speaker.
it whould start off with a hiss then do the wump sounds and it got faster and turning the volume up did supress it.
i replaced the amp and it stopped.
found part of the problem (which i had thought was the whole problem). the remote wire is run under my seat and then to the back. apparently it got caught on the rail and got cut open slightly, so i taped that up and it solved it being a continuous problem. so, now the sub will hit the 2 times and then it starts happening again...

im thinking of just re-running the remote wire. is there a way i could just tap into the antena from in the trunk?
if it's a power antenna...yea.
but a regular one nope.
well of course its a power antenna, other wise i wouldn't have suggested it, silly.

does anyone know what that extra plug is that is connected to the strand of wires that run to the ant? i've looked everywhere and there is only a male adaptor, im confused to what its to...
alright, i took the remote wire and tapped directly into the antenna in the trunk, but when i plug in the rca's i still get the pulsing, the power is just fine when the rca's are out. could the rca's be considered "grounded" as well and give this effect? if so, im going to have to tear the entire inside of the car apart to try to find where the rca's are grounded to...
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