I know I'm not the first, nor will I be the last, person to struggle with the dreaded group loop isolation problem -- but I've already done some investigation, and I'm looking for feedback to perhaps minimize my hassle dealing with this issue.
Environment:
* 200 AMP High Output Alternator
* "Big Three" Electrical Upgrade
* Kenwood KDC-MP3035 Head Unit
* Infinity 6010CS Component System door speakers
* Pioneer TS-A6962R rear 6x9 speakers
* Pioneer GM-X544 Amp (4 x 50W RMS - Cabin speakers)
* Kicker ZR-360 Amp (1 x 400W RMS - Subs)
* 2 Alpine SWS-1223D Type-S 12" Subs
* Generic Dual-12 sealed box
* 1 farad Cap (added after this all began, so momentarily ruled out as cause)
Issue: I get alternator noise, very noticeable. Only audible through the component tweeter on the driver side. Can get better or worse, but always comes back with a vengeance if I pump up the volume a bit.
This evening's investigation:
1) I could hear a faint hum coming from the same speaker for a few seconds even after shutting off the car. I happened to notice that this same noise physically comes from the alternator if I run up and stick my head under the hood, so I guess it still counts as alternator noise.
2) Cutting main power from the battery to both amplifiers eliminates the noise.
3) Removing the RCA inputs on the Pioneer amp (which powers all cabin speakers) makes no difference.
4) Removing the Pioneer amp on-board fuses does not stop the alt noise, though it does change it to a "softer" sound.
5) Pulling either speaker wire from the amp for the problem door speaker causes the noise to get much louder. Pulling both causes it to stop.
I have cleaned and re-bolted the main grounds of the car, both at the front supporting the Big-3, and in the trunk for the amps. I'm using a strut bolt for trunk grounding, with the paint sanded away from the base first. The only faux-pas I can think of is that I've shared the grounding point between both amps and the cap. The cap is on a run of 4-ga, and the amps are daisy-chained on a second run of 4-ga.
So basically I'm still trying to figure out if this is a power issue, or if there is something nutty in the wiring between the amp and the door speaker. The component set also has a passive crossover in the door, so there are quite a few wires in that area. Any thoughts on the next place to prod this PITA? Thanks in advance.
Fun fact: The "pop" of feedback resulting from a hot removal of the signal RCA to the Kicker amp causes enough momentary alternator load to very nearly stall my car.
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so if your saying that the noise only comes from the left speaker, you can narrow it down very quickly. first swap the left and right rca's on your highs amp. if the noise switches to the right side you know its coming from further back, if its still the left speaker u know the noise is comingin between your speaker wire going to that speaker, . next pull your speaker out of the door and hold it. does it still whine, if not adjust your mounting points. maybe isolating the metal of the speaker frame with the metal of the car. try a new piece of speaker wire ran from the amp directly to the speaker, if the noise stops you proabably are picking up noise along the speaker wire.
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Might have found a major reason.
Apparently these things don't necessarily like being on the outside of the vapor barrier. Not too surprising, in retrospect, when the inside of the door was like a fresh morning dew when I opened it. So now I get to try and find out if this thing is toast, or whether the moisture alone was causing the problems.
Note that the other stuff stuck it it is residue from sound-deadener material.
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sndsgood wrote:so if your saying that the noise only comes from the left speaker, you can narrow it down very quickly. first swap the left and right rca's on your highs amp. if the noise switches to the right side you know its coming from further back, if its still the left speaker u know the noise is comingin between your speaker wire going to that speaker, . next pull your speaker out of the door and hold it. does it still whine, if not adjust your mounting points. maybe isolating the metal of the speaker frame with the metal of the car. try a new piece of speaker wire ran from the amp directly to the speaker, if the noise stops you proabably are picking up noise along the speaker wire.
Thanks -- those are some things I might still need to try, if this corroded crossover and wet wiring isn't the culprit.
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sndsgood wrote: try a new piece of speaker wire ran from the amp directly to the speaker, if the noise stops you proabably are picking up noise along the speaker wire.
this is exactly what i was thinking. i wouldnt stop at the speaker wire though. test all of the wires by running a seperate wire. unless like you said, the crossover was your problem. that thing looks horrible. are you sure you didnt mount that thing underneath the car???
i have my crossovers inside the door panel also, so i'll remember to look out for that in the future.
i have 2 of those crossovers brand new, if you need em gimmie a pm we can work something out.....
illdwes . wrote:i have 2 of those crossovers brand new, if you need em gimmie a pm we can work something out.....
PMed. No sense waiting for these things to rot.
I should probably check to see if I covered over the oiling/drain holes when I laid down sound deadener. That probably isn't helping things.
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The main thing I needed to finish isolating the problem was some extra speaker wire. I've picked that up, along with some heat shrink, and I should be set to fix this tonight. I'll move the crossovers inside the door, of course.
I'll still be looking for new ones, but for the moment it looks like these ones aren't any worse for wear on the inside. Corroded terminals FTL.
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Thanks everybody for your help. I've done some splicing, soldering, and relocated the crossover to the inner cabin. I think the problem was a combination of two things: 1) The crossover and associated wiring was wet. I had noticed that the noise got worse on rainy days, and this would explain why. 2) The terminals on the woofer are tight against the top of the mounting opening, and the connectors were poorly protected at that spot. Either of these could have been making electrical contact.
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