Bad Alternator Whine!

[gedwyn]

First off let me say that this is my first time posting here as I am the proud new owner of a mint
'99 metallic black M3 convertable. Best car I have ever owned. However,I have installed a new JL Audio
stereo system as the HK stereo was Horrid. Well it sounds great except for bad alternator whine
coming through the rear speakers. I have moved both amps ground to the battery and several places on the frame
to try and get rid of it but no luck. I am hoping somebody will have experience with this. My amp are in the trunk with the speaker wire going through each side by the seat/Rear window panel and into the speakers.
The whine stays on no matter if the amps are on or off which makes me wonder if the speaker
wire is picking it up and it is not a ground issue.

Thanks for the help in advance.

Paul

 

[Tom]

Does your amps have a gain dial on them? If so try turning that down a bit. From the deck, are the amps connected to an EQ or Crossover?

 

[gedwyn]

They have an input gain. Is this what you mean?
But if the whine still exist with the amps off then is it really the amps?

Paul

 

[Tom]

How did you install the Headunit? Did you purchase a wire harness or cut the stock wires? If your speakers are connected to the amp, I'm not sure how they can whine when the amp is off unless perhaps the wire is exposed somewhere. Go through and check to see if this is the case.

 

[j2azz]

Alternator wine has NOTHING to do with input gain. It will still be there no matter how you adjust that. That cause of your noise is the power cables are too close to your RCA (Pre-outs). The Power cable emits EMF which gets picked up into the RCA cables and is played through your system after being amplified by your amps.

I almost can bet you ran your RCA's and Power cable down the same side of your car. You should always run them on separate sides, and IF you need to have the wires come close to eachother, you need to have them cross eachother perpindicular to eachother and the noise will be cancelled out (not really cancelled, but the EMF won't be picked up do to the direction of the waves).

Another option to try if you can't run on either side of the car is pick up BETTER RCA's that are actually shielded well. They will block against the EMF, but you still may get whine.

Let me know if this suggestion helps at all.

 

[j2azz]

and I am also with Tom.. How could you experiance whine if the amps are off? There will be no signal going to the speakers...

Did you mess up the install and bi wire them to the head unit and the amps? heh.. That could be a cause of loop grounding.. Thus you'll get wine and probably blow out your head unit and or amp. Thats the only thing I can think of if your speakers still work with the amps off....

 

[j2azz]

Oh, and always ground to the frame, NEVER to the battery.

You want your ground from your amps to all be located at the same spot on the frame with the smallest amount (shortest distance, I don't mean thickness) or wire. If you have grounds connected at multiple spots in the car, you will get a ground loop, and also have noise issues.

Also, if this is just your back speakers, I go to my original guess with the RCA's. I bet you have 2 or 3 sets running to the back of your car. Front/Back/Sub. I bet the RCA carrying the back signal is the closest to your power wire..

Did I guess correctly?

 

[gedwyn]

Well here is the deal. I have the RCA's from the head unit going on the left side to the back in the truck connected to the amp. Since the battery is located in the trunk the power cables are not even near the RCA's.
The power cable goes right from the amp directly to the battery in the trunk. The negative ground on the Amps are going to the same bolt in the trunk where the CD changer used to be.. I did not install the head unit so I am not sure how it is grounded. I thought of taking the head unit out and maybe grounding it back in the trunk
with the amps (In case of ground loop) but I am not sure how to take the unit out? The Power cable and RCA thing makes sense though as to why I get noise with the amps off. I wonder what will happen if I disconnect
the speakers from the amps. Will I get noise? I will try this next.

 

[j2azz]

I wasn't thinking. My last car had the battery in the front, but I forgot the M3's had it in the back. Here is what you try next. Turn the system on. Get your alternator whine. The RCAs going into the amp powering your back speakers, unplug them while everything is on. You might get a pop when you unplug them so do it quick. If the whine goes away, you know the noise is coming from the RCAs. IF you still get whine with the RCAs unplugged, its a problem with your amp and a ground loop/bad ground. Make sure the ground connection to the frame is filed and clean metal so the contact is good. Also, what size amps and what size ground wires are you using?

 

[gedwyn]

OK. Here is an update. It even exist when I totataly disconnect the speaker wire from the amp and the Head unit and amp are turned off. It is not as loud but still discernable. I guess the amp just amplifies the whir. So thismust mean that the speaker wire is picking it up some where no? Hmmm. My wire is not near any red power line so where is it getting it from. This is crazy.

 

[gedwyn]

Iam using 4 gauge ground wire and my amp are JL audio 450/4 and 500/1. But like I said, I am getting it with evrything off and the speaker wire disconnected from the amp.

 

[j2azz]

When you says speaker wire, do you mean the speaker wire between the speaker and the amp, or do you mean the RCAs between the amp and the source?

 

[j2azz]

If you mean the speaker wire between the amp and speakers and you totally disconnect the speakers from the amplifier so they have nothing going to them. The ONLY possible option is the speaker wire is crimped somewhere and is actually making a connection to a positive source somewhere. That is HIGHLY unlikely, so I assume you are talking about the RCAs between amp and source...

 

[gedwyn]

Actually I am talking about the speaker wire from the amp to my speaker crossover box next to the speaker. Then it goes to the woofer and tweeter. Could the box maybe touching something? the speaker wire is fine I checked it a million times.

 

[j2azz]

Does it come through both the tweeter and woofer, or just one of them?

 

[j2azz]

the whine that is..

 

[gedwyn]

OK. I moved the crossover box but still no dice. It seems to be coming from the front speakers as well. Just not as noticable as the back speakers. This is killing me.

 

[gedwyn]

The whine seems to be only coming from the tweeters.

 

[j2azz]

How are your tweeters mounted? Any metal contact to the frame on them?

This is pretty strange if there is no source going to the speakers, they just have wire attached, but it doesn't go anywhere, and you get whine...

They could be grounded incorrectly where you have a leak somewhere through your electrical system that is getting grounded out??

Honestly, I think u have a source going to your speakers that you don't know about, because they Shouldn't make ANY noise if they aren't even attached to the amp.

 

[gedwyn]

OK. I have been doing some experimenting.
1. If I totally disconnect the speaker wire (Not RCA input wire) from the crossover box and pull the box outside of the door from where I have it No Sound. The moment I put the box down in the well I get the sound bad.
which means the crossover box is picking something up from a factory power wire down below.

2. With the box out and no whine, I run a speaker cable from the box, Outside of the car away from the well.
When I plug it into the amp: Whine. Unplug it from the amp: No whine.

I am assuming then that the whine is coming from A: Some factory wire down in the well that was running along side my Crossover box and B: The amp itself.
So it is coming from two different places making it very loud.
So what do I do now. The amps are brand new by the way.
Also, why did the factory stereo not do this? The speaker wires for it were in the same place.

Paul