Thumping from the subs

Recently i had a buddy of mines that had an install that had an issue that i couldn't understand....the subs in the rear sometimes (if you turn it up loud) would thump together......they would literally go up and down (not following the beat) in unicy in a constant motion.....your thoughts on this?....thank you*paw print*

What type of amp is he running? HU?Nik

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oonikfraleyoo wrote: What type of amp is he running? HU?

sorry about that....he actually has an alpine HU and an mtx amp pushing 2 mtx thunders 15's....

*paw print*

I had an Alpine 9815? Anyway, after it aged a bit, it did something similar. My sub would move in and out even when there was no music playing. It made very little noise (kind of a "digital" sounding chirp, very quite) It never "thumped " at all though. That could be a starting point. If you have another HU available, switch 'em. If thats not it, do the same with the amp.Nik

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oonikfraleyoo wrote: I had an Alpine 9815? Anyway, after it aged a bit, it did something similar. My sub would move in and out even when there was no music playing. It made very little noise (kind of a "digital" sounding chirp, very quite) It never "thumped " at all though. That could be a starting point. If you have another HU available, switch 'em. If thats not it, do the same with the amp.

i remember having something like this happening to my older deck (chirping of the subs with my pioneer) as well.....thanks for your input...i'm afraid i don't have another to run a test on.....it seems like a grounding issue though, but i checked all of my grounds....solid and nice and clean...

*paw print*

actually there might be a low singal on one of the channels but wat i think it is there is no divider in the box of the 2 subs so all the air is together whcih makes one go up or down , plug one speaker only and u can see that the ohter moves a lil bit , but that can damage the sub i would prefer a divider in the box or a new boxRockford Fosgate

This is sometimes caused by overmodulation of the amplifier input stage, caused by gain set too high or by output voltage from the HU greatly exceeding the amplifier input capability.  It can also be caused by feedback errors inside the amp or the HU.  Try turning down the gain and see if the condition clears.Support the12volt.com