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whine coming from speakers


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jdog0411 
Copper - Posts: 150
Copper spacespace
Joined: January 05, 2005
Location: United States
Posted: March 11, 2007 at 12:54 PM / IP Logged  

I just got finished installing my new system in my 2004 BMW 325ci. I am running an Alpine 9885 head unit, JL XR series components in the doors, and no rear speakers (to port the bass from the sub in the trunk  to the cabin through the rear speaker openings). I am running a JL 250/1 for the sub and a 300/4 for the components in the doors (bi-amped).

I am experiencing alternator whine coming through the speakers when the system is running with the car running. There is no noise when the system is on but the car is not running. The whine increases in pitch with the engine rpm and decreases with engine rpm. It can be pretty audible while the music is at low volume, and barely noticeable at volume, or at speed.

I took pretty good care to avoid noise by running my signal RCA's down the driver side of the car, while the power cables in the car run down the passenger side. I have the ground attached to the factory ground point for the other grounds in the system in the trunk. The only thing I can really think of is that my rca's overlap the ground cable on their way to the amps which are mounted in the trunk. Could this be the issue?

Any other things I can check as a possible culprit to this?

2004 BMW 325ci.
Alpine CDA-9885
JL 300/4 and 250/1
JL XR 5.25 comps
Infinity Kappa Perfect 12
rudydapimp 
Copper - Posts: 390
Copper spacespace
Joined: February 27, 2006
Location: United States
Posted: March 11, 2007 at 12:58 PM / IP Logged  
i would  check it with its own ground.  (meaning make your own, not the factory one) heck, run a temp wire to neg terminal on battery and use that as ground and see if that takes care of it.
jdog0411 
Copper - Posts: 150
Copper spacespace
Joined: January 05, 2005
Location: United States
Posted: March 11, 2007 at 1:03 PM / IP Logged  
Ok, I'll try something like that....just so I'm clear, I am running my own ground cable (two 8 guage grounds running from each amp, to a ground distribution block, with 4 guage ground going from that to the ground point in the trunk. There is 4 guage power wire running to each amp. Would any of that make a difference?
2004 BMW 325ci.
Alpine CDA-9885
JL 300/4 and 250/1
JL XR 5.25 comps
Infinity Kappa Perfect 12
danwood 
Member - Posts: 3
Member spacespace
Joined: March 12, 2007
Location: United States
Posted: March 12, 2007 at 1:42 PM / IP Logged  

The way you run your power and ground wires shouldn't give you a signal noise because of interference. The problem is most likely your RCA cables. Are you COMPLETELY sure that there isn't any power or ground source running near them? Beamers have like a billion miles of wiring in them and you might be getting a signal from something that you don't even know is there. It dosen't take much to get a whine. If you find a place that there might be a problem, but you can't run your wires anywhere else try insulating them. Hope this helps

jdog0411 
Copper - Posts: 150
Copper spacespace
Joined: January 05, 2005
Location: United States
Posted: March 12, 2007 at 10:41 PM / IP Logged  

This isn't really a noise in the speakers, it is alternator whine. It corresponds with the rpm of the engine. From everything I've read here, that indicates a ground loop condition or other faulty ground. I haven't had a chance to check it yet, but I plan on doing that tomorrow. I hope to god it is a ground issue and not a problem with the RCA's...it was pure hell running those rca's to the trunk. The car is built like a tank and taking it apart and running cables is not something I plan on doing again.

Thanks for the responses..hopefully I'll get this nailed. I've been installing this system for two weeks now, and it is just about finished except for details like this.

2004 BMW 325ci.
Alpine CDA-9885
JL 300/4 and 250/1
JL XR 5.25 comps
Infinity Kappa Perfect 12
forbidden 
Platinum - Posts: 5,352
Platinum spaceThis member has made a donation to the12volt.com. Click here for more info.spaceThis member has been recognized as an authority in Mobile Audio and Video. Click here for more info.spacespace
Joined: November 01, 2003
Location: Alberta, Canada
Posted: March 13, 2007 at 1:24 AM / IP Logged  

Unplug the rca cables from the amp and plug in a set of muting plugs. Muting plugs can be made by taking a old pair of rca cables, cutting the end off leaving about 3" of wire. Splice the inner and outer section of the wire together. This shorts the wires together. Plug them into the amplifiers. Do this to all input, if there is no more noise when the vehicle is running, chances are highly likely that you need to start looking at the deck. Read the what is a proper grounding sticky and the Q&A thread as well. There is ample things to read about that may point you in the right direction.

Top Secret, I can tell you but then my wife will kill me.
jdog0411 
Copper - Posts: 150
Copper spacespace
Joined: January 05, 2005
Location: United States
Posted: March 13, 2007 at 10:43 AM / IP Logged  

Thanks Rob.....your input is highly valued.

The issue has been resolved. I feel kind of stupid for leaving this part out of my initial post about my configuration, since it turned out that there wasn't really a problem afterall. I have two JL amps, a 300/4 for the components, and a 250/1 for the sub. Both amps were all wired up and ready to go, but I had not hooked up the speaker wire to the sub yet. The rca's were plugged in, but I hadn't actually connected the sub to the amp. I don't know why that would be a problem, but now that I have hooked up the sub, the whine is gone.

Although I'm happy that the system is quiet now, I would like to make sure that there isn't an issue that is being masked somehow. Why would everything be noise free once the sub was hooked up to the amp? Is it still possible that the sub amp has a bad ground or there is some other issue that is being masked because the sub isn't reproducing the frequencies? Both amps have 8 guage wire going to a single distribution block, which then in turn has 4 guage going to the factory ground bolt in the trunk.

Anyway, thanks to everyone, and the ground sticky was very informative and helpful while I troubleshot this problem. This forum is an invaluable resource to those of us who take on car audio installation with limited knowledge and experience.

2004 BMW 325ci.
Alpine CDA-9885
JL 300/4 and 250/1
JL XR 5.25 comps
Infinity Kappa Perfect 12
audioman2007 
Copper - Posts: 580
Copper spacespace
Joined: February 20, 2007
Location: United States
Posted: March 14, 2007 at 7:20 PM / IP Logged  
wait..... you have 4 gauge power   and 2 8 gauge grounds?
jdog0411 
Copper - Posts: 150
Copper spacespace
Joined: January 05, 2005
Location: United States
Posted: March 14, 2007 at 8:13 PM / IP Logged  
No, I have 4 guage power going into a fused distribution block, with 4 guage power being run to each amp. Then I have 8 guage ground going from each amp, to a distribution block with  a single 4 guage wire going to ground. So the power and ground are both net 4 guage.
2004 BMW 325ci.
Alpine CDA-9885
JL 300/4 and 250/1
JL XR 5.25 comps
Infinity Kappa Perfect 12
arrow12 
Silver - Posts: 527
Silver spacespace
Joined: October 06, 2005
Location: United States
Posted: March 14, 2007 at 10:10 PM / IP Logged  
Correct me if I am wrong, but I thought a general rule of thumb is have the same gauge power and ground.  You have a 4 gauge wire running into a distribution block which splits into two more 4 gauge power wires, right?  Then why wouldn't you do that the same on the ground side?  Instead you chose to use two 8 gauge wires instead of two 4 gauges.
That's my opinion. Take it, leave it, or correct me.

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