QuestionQUESTION: My younger brother has a 1994 Camaro that i am replacing the head unit on. When we bought the car it had a professionally installed Dual head unit (not sure what model). The car has a factory Bose system in it. The bose sounded 'ok' with the dual head unit and then the dual just gave out and the screens wouldn't retract and basically fried. 6 months ago my idiot brother decided to go to wal-mart and get a cheap ass VR3 or something like that, after he bought it i read some reviews on the head unit and it turned out that no one likes them, so against my wishes he replaces the dual unit with the VR3. But, as i suspected, the VR3 constantly has a high pitched whistle that only turns on when the unit is on and only is off when the unit is off. He drove the car this way for about 5 months until this last week, i finally got enough sense knocked into the kid that he needed more of a name backed stereo. So i had a friend willing to sell my brother his Pioneer (MP6700 i think). 2 weeks ago my brother bought some subs from another friend of mine with a box and two 10' Pioneer subs (not sure on what model) the subs did not come with an amp, so my brother bought a Rockford Fosgate amp (also not sure what model). So i installed the amp, and sub box into the car and wired them to the VR3. The VR3 did not have sub outputs so i messed around with the Rear RCA outputs and the Front RCA outputs trying to figure out what sounded better. But even though i had the amp cranked for output power the subs didn't do anything. So i then installed the Pioneer head unit today and everything sounds awesome except for the subs. For some reason the subs (when hooked up and turned super low) constantly thump really hard and dont even go to the music, even when the car is running and shutoff, i ended up separating the power wire to the amp and the RCA outputs from eachother and rewired the remote from the headunit and it still thumps with no constant beat or anything. I made sure the headunit sub stuff was either super low or off and the subs still do it, so i guess i don't know what to do for now.
ANSWER: Had a hard time keeping track of all the history so forgive me if I don't hit the nail on the head.
I suppose you have what is called "motor boating". It is generally caused by multiple grounding or bad grounding; especially, when there is a ground loop AND a bad ground it causes this - it is actually a form of low frequency oscillations or instability.
So, check the grounds making sure they are all good solid chassis metal to metal, tight ground connections.
Sometimes you must take the sub amp ground back to the same point as the head unit - or even all the way back to the battery. So, experiment with that and see if that will calm it down.
Further, if you are getting too much audio level to the sub you may want to put a pad or some resistance in line with the input to the sub amp to bring the level down, but that is subjective and you should base that on whether or not it sounds right.
Hope you get it going.
C
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QUESTION: haha, its kind of funny you mention the ground loop. I actually bought a 'ground loop isolator' (Scosche model ES-034) AND i rewired the ground wire from the subs to the ground on the battery, but i still get that 'motor boating' noise. I actually got the subs to work a little bit like they are supposed to, but anytime you mess with the 'punch remote' the subs act up again with that odd thumping. Would it have to do with something in the amp? i guess thats my only idea at this point.
AnswerThe Scosche model ES-034 ground loop isolator is for the signal side of things and not the power side, I think.
I still recommend you take the ground wire for the amp all the way back to the negative terminal of the battery and see how that goes.
Let me know.
C
