Hi guys, I had installed a set of component speakers and a new head unit this summer in order to improve the sound in my car. Ever since then the sound quality has been terrible due to a whine I get when the engine is on. The components are amplified and I also do have two sub woofers hooked up. When the sub woofers' amp is attached to the battery it only makes it worse. I had the amp for the components regrounded and it took care of a bit of the problem, however when I accelerate the whine becomes unbearable for me to even enjoy my music. Anyone have any idea what might be causing this? The audio shop that looked at it told me it was either the headunit or a ground somewhere in the car. Unfortunately I wont be able to tear apart my car for another few months due to school and the cold weather. If it is a ground somewhere in the car, does anyone have a list or diagrams of the locations of grounds in the car? Any insight into this topic would be much appreciated, as all I want is to be able to rock out without having to have noise interference.

 

check out the big 3

 

I think they call this alternator whine or something. So first, help me get a better understanding of your setup.

You have 2 subs in the trunk with an amp, and new component speakers with a second amp driving them, correct? How much total wattage are you running?

I am assuming the whine is coming from your component speakers and not the subs?

I think the audio shop was on the right track when they regrounded the amp. I'm sure they know to use the same gauge ground cable as the power cable. Your ground cable should not be longer than 18" (at least that's what I've always been told). Make sure the ground connections are completely solid. For example, you use connector around a bolt, and all of the paint is sanded away to bare metal. I assume your amps are mounted in the trunk. A good spot for a ground is one of the bolts to the gas tank on the lower left or right. You will have to get a second nut (metric), but the bolts are long enough. That's where mine is grounded.

Another thing that can cause interference is if they run your RCA cables next to the power cables. Good installers always run them down opposite sides of the car.

Since you have two amps, I should ask. Did you run separate power cables for the two amps, or do they share one power cable? What gauge is/are the power cable(s)? If they share one power cable, you need to make sure the gauge is heavy enough to support the power of two amps. How is the power split between the two amps? Was a distribution block used, or is it "daisy chained" by going through one amp to the other?

Oh, and here's another thing you can try to test if its your head unit making the whine. Take an ipod, or a home cd player with an extension cord... or any device that puts out low-power signals, and plug it directly into your amp through the RCA inputs. Play some music. On second thought, an Ipod or something that has volume control is necessary, since it will mimic your headunit better. Turn on the car and make sure your head unit turns on (so leave the face plate on, etc) so that the amp will also turn on. Play your music. fiddle with the volume and see if the whine is there.

If it is, then it's either your amp that's effed up, or its your power/ground connections. I suppose it could also be a speaker wire issue. If it isn't there, it could be because the power/ground on your headunit is messed up, your headunit itself is messed up, or the RCA and power cables were run down the same side of the car causing interference. See where I'm going with it? THat's an easy test.

Let me know how it goes. I'm afraid if you're unable to take your car apart for a while, you might have to live with it.

This post is becoming long, but I thought of another test you could try. After you do the "ipod test", and find that the problem persists (i.e. it's either your amp, amp's power/ground, the RCA cabling, or speaker wires), take a home stereo speaker and plug it into one of the speaker outputs on your amp. Test that out. If you continue to get whine in each channel you test, we've ruled out speaker wire issues.

Frankly, since the noise increases with RPM's, I'm afraid it may be an alternator issue. It actually sounds like it probably is. SO. if you're not sick of testing, check the power and ground leads coming out of the battery. Make sure they're clean. Check the power and ground connections coming from the alternator and make sure they are clean and solid also.

If you're running a ton of wattage, you may need to do the "big 3" upgrade of your wiring between the battery, alternator, ground, chasis, etc. Go to a car audio forum and search for it... or just google "big 3 car audio" and you'll get tons of stuff.

EDIT: looks like crr already pointed you to the big 3 while I was being long-winded!

 

wow bigpete, thanks for that reply, im gonna go try the ipod idea now. I'll attempt to get you the specs on everything while I'm out there fiddling with stuff, stayed tuned for my updated post.

-edit

ok here goes my long winded post. The problem is with the components and not the sub woofers. When the audio shop regrounded the amplifier it eliminated the "helicopter" noise I was getting out of the midbasses in the doors. There are two different power lines going to the amp, both directly connected to the battery. Neither my local shop, or the shop up at school (which regrounded the amp) said anything about this.

First of all I am running two separate amps, one is for the component speakers in the front and one is for the two sub woofers in the trunk. I installed everything in the car myself. I'll begin with the amplifiers. I did run the rca cables for them down the middle of the car, and the power cables down the passenger side. First mistake I made in my 190 was I ran the rca and power for the amp and subs down the same side, although it never created problems. Anyway, so yes the rca and power are separated. Powering the Boston Acoustic S60 component speakers is an Alpine MPV T320. The subwoofers are two Rockford Fosgates, 10". I threw out the boxes, and I honestly don't feel like taking one out of the enclosure to figure out the model and specs on it. The amplifier is also a rockford fosgate 1200w amp, more than enough juice. I had this subwoofer set up in my old car and it worked perfectly. My headunit is a pioneer DEH-P780MP. Hopefully that clears up some things for you. I just ran outside and did the ipod test, there was no whine while I was doing that. Does that mean the head unit is faulty? I had the engine running and drove it up and down my driveway, granted this isnt the open road, but I would hear the whine while I was driving in my driveway regardless.

after rereading your post I too wonder if it is the ground for the head unit itself, any suggestions on how to reground it? I'd like to eliminate this problem as I have invested a lot of money and time into the thing and all I want to do is listen to music that doesn't have an annoying whine which I have to drown out in a vain attempt to enjoy the music. my ear drums hurt

 

its very possible that it could be the headunit...where did hook it up to the negative or ground it to the chassis?

 

the headunit is currently grounded to the stock grounding wire that was used for the stock radio. I was wondering where and how else I might attempt to ground it to determine whether the issue is just a simple ground or if it is the head unit itself.

 

try grounding it to any metal around the head unit? a friend of mine had a problem like that. instead of using the stock grounding i grounded it to his chassis directly and the problem went away

ps...i think his problem was the more powerful headunit needed thicker/shorter grounding wire

 

any ideas on location though? that is what I'm getting at, i didnt see any metal directly in that area.

 

sorry, cant help you on that one...its been a while since i took out my head unit. there has to be some around there tho; it is a benz after all

 

ok i have the console somewhat apart, i noticed that in the passenger footwell there is a nut at the top with bare metal behind it, would that be an acceptable grounding point or do i need bare metal on the body itself, would runnign it directly to the battery be another option?

 

take a look at the big 3 link i, uh well, linked. it says you should ground the battery to the chassis, so by grounding to the chassis you are essentially grounding to the battery. the screw you found should work fine tho

 

ok after some toying around i determined that it the ground isnt the problem. To be totally sure i am going to check with best buy and circuit city to see if they still carry my radio, im gonna buy one and test it with that, if that works then i know for a fact it is the radio.

well no one carries the radio, the only place that does sells it for 390 bucks and its a store credit upon return....can't do that, looks like i'll have to wait until monday to take it to a service center to be repaired. I hope its teh radio, thanks for your help/

 

out of curiosity, what type of radio is it? and did you try the alternating thing on the big 3?

 

http://www.pioneerelectronics.com/pn...159491,00.html

 

Cool, I'm glad the ipod test helped narrow things down for you. Since the issue is with a relatively low-power unit (the head unit isn't sucking much juice since you have external amps), I don't think the Big 3 is going to do anything. I'm assuming that you have the ability to turn your head unit's internal amplifier off, right? I have a Nakamichi unit, and I can turn mine off. Apparently its supposed to help the sound quality.

But it will also lower the power requirements of your head unit. It might be as simple as reducing the amount of power it needs, which thus would eliminate the need for a ground that exceeds the requirements of the stock wiring. Just a thought.

Otherwise, you're on the right track. You'll just have to look around to find a good grounding point. Honestly though, I would be surprised if that's the problem. The MB engineers probably knew what they were doing when they set that up, so unless something has corroded, I would bet on your head unit being the problem.

But don't rush out and buy a new one until you've tried to shut off the internal amp first, then tried to reground it second, then taken it to a profressional for testing third.

 

my dad helped me when he saw me out there toying around with it, he showed me something. I took off the door sill and grinded away some paint to create a new grounding point. That did nothing. There is no internal amp that I know of and I have played around with all of the settings a bunch of times. I am just gonna take it to a repair shop tomorrow and hope for the best. Thanks for all of your help. At least I feel more confident that I didn't screw up the wiring and such.