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Sub thumping

1907 Views 13 Replies 8 Participants Last post by  adambeazley
Lately, as in the last couple of weeks, I've had some strange thumping from my Alpine MRD-M301 and the Alpine SCS-1042D. I bought an adapter on eBay for my RCA-outs (although I could've made them myself, didn't learn how until later). I did the installation myself.

This happens whenever the car is started. A few seconds later, whether or not the radio is on, it randomly thumps. It can last from 2 to 10 seconds. If the radio's off, turning it on doesn't make a difference.

What are the symptoms of this and what can I do to fix it?
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I experienced this when I still had my stock HU with the sub out adapter (also from ebay). My friend said it was the power lead turning on the amp/sub. I've since replaced the stock HU with an Alpine and have not had the problem since.
Also, check to make sure you have a good solid ground.

my friend managed to blow two subs this way....the problem we discovered after the fact, was a badly chosen remote wire for the amp, it cuased a power spike everytime the deck truned on or off, and if u watched it when it happened the excursion of the sub was insane, it was like the sub was literally jumping out of the box....if this is happening check all of ur connections, if it continues after any quick fixes take it to an installer
I'm going to assume it's the ground connection. It's secure but it's on a seat bolt. I read a while ago that that's a bad idea, but I didn't see the harm and I did it anyway. Guess I should take peoples' advice. I'll check the remote wire too, for troubleshooting. But until then I guess I'll unplug it. Thanks everyone for responding.
sounds like u got a handle, good luck
on the alpine you can set the amp on delay time.. sometimes doing this will fix it... as the spike has passed before the amp turns on. i normaly set mine to 2 sec anyways, so it doesn't turn on then off when i start the car.
Thanks for the tip striptyler. Would've been nice if you had told me that before I took everything out of the car
Nah, I need to redo the wiring regardless, I did a horrible job because I wanted to just get it in the car, and it was really hot that day! I'll remember the turn on delay time, but I thought that delay was for when you connected multiple digital amps or something. Thanks!
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There is also an amp delay time, you are correct. I may be wrong with your model but i believe it has the delayed turn on. Check the manual to be sure. If it is only the amp timing delay, and you set it to 2 seconds, it will sound like crap... hitting 2 seconds after it's supposed too... wouldn't be the drummers fault he had no rythem.
In my kicker manual it says one of the best grounds is the seat bolt, but they also say you will need to sand any dirt or paint off to get a really good ground, and I have never had a problem since, it works perfect for me, no pops or anything of that nature

soundguy, where else would you ground it?
to revive an old topic, that has recently been re-introduced, grounds should never exceed 18" well as all other things mentioned
def a ground problem here...try grounding it to something else
It was only a one foot ground so I know that wasn't it, so I think it was the fact that I had it on a seat bolt.
Im not sure if you are still fighting this problem but if so read this link:
I put a tutorial on how to make a turn on delay with about 5 bucks in parts from Radio Shack.
Good Luck
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