How to remove engine noise from my subwoofer

[twithers]

When my amp/sub is on, it rumbles from the rpm of the engine. It adds some rumble to my motor, but it's annoying. So, when I turn on my head unit, it turns on the amp by remote and with the volume on the head unit turned all the way down, as soon as the amp comes on, you can hear the engine in the sub. You can also put your hand on the sub and feel the rumble, just like if you had your hand on the engine.

I can also hear the bump when the power locks or windows switch is used. A low frequency pop when the contacts in the switch are made.

How do I remove this unwanted interference in my audio system?

Would that all be removed by adding a capacitor to the power wire?

Some sort of noise filter installed somewhere in the system?

Thanks.

 

[beardeddummy]

That's an odd one. I've only of a whine frome the alternator. Maybe some sort of interference is all your grounds intact?

 

[twithers]

Yeah, I've got my wiring pretty simplified. Main power in a big cable straight from the battery. The switched power tapped off the fuse box and the ground bolted to the floor with one of the seat mounting bolts.

 

[Black_cirrus]

Make sure your engine and body grounds are good. Especially the body to engine strap.

 

[someotherguy]

Yeah go over -all- your factory grounds first, as it's almost certain you've got problems there.

Then, power the HU strictly off a fused feed from the battery, not from the dash harness. The dash grounds ain't great. You'll lose the ability to do a "key on" control of the power to the HU but I've always preferred it that way so I could play it without the key.

Richard

 

[jkeaton]

Are you using quality RCA cables?

 

[df2x4]

Another thing to consider is a ground issue inside the head unit itself. For example, older Pioneers were notorious for having poorly grounded RCA jacks which could induce engine noise and interference to connected amplifiers. A quick way to test this would be to wrap some stranded copper wire around the base of your RCA jacks and ground them to the radio chassis with a small machine screw. If the problem goes away then you've found your issue.

I agree with Richard though, it's more likely a harness ground issue or something similar.

No, a capacitor will not help you. Capacitors don't really help anyone in car audio, unless your goal is to spend money for no actual gains.

EDIT - I have no idea how I missed this the first time reading through here but...

The switched power tapped off the fuse box and the ground bolted to the floor with one of the seat mounting bolts.

This is a GIANT no-no. Any amplifier grounding point needs to be bolted DIRECTLY to the body, with all the paint beneath your terminal sanded off so as to make good metal on metal contact. You're talking high current grounds here. I've seen people get away with this, but I cringe every time I see someone ground an amp in this manner. Fix that before you even mess with anything else.

 

[twithers]

Ok, thanks for all the advice. I went out today and did some ruling out. I powered everything up, but kept the volume down, so all I could hear was this rumble in the subwoofer. I unplugged the rca's from the amp and the rumble went away. Strangely enough the rumble is about twice as loud on the red channel as it is on the white. Weird. Plugged the rca's back into the amp and disconnected them from the HU and the noise went away again. I got a different set of rca's and strung them across the cab between the HU and the amp and the noise was the same as with the original rca's.

So I would guess that this narrows it down to something to do with the HU and/or it's wiring. I do prefer to have the switched 12v hooked up, so is there a preferred place to connect that instead of the random terminal in the convenience center. And does the ground for the HU need to in a special place or even straight to the negative terminal of the battery as some people suggest for the amp?

On a wild hare note, could this problem be caused by something going on with the alternator? I don't have anything major going on with the alternator specifically, but I do get random electrical wierdness from time to time that I'm still trying to figure out since I just recently bought the truck.

Thanks.

 

[steampunk1375]

90‰*of the time electrical gremlins are caused by bad grounds. Start there. Re-do the ground from your amp to the chassis first, then check battery to chassis and chassis to engine.

 

[Black_cirrus]

Alternator noise is rare but possible and usually shows up in highs not bass. How do you have the deck grounded? make sure its grounded well take a multi meter with the system running from your deck ground to the amp ground and see if you get over .1 volts. The yellow wire to the deck (unswitched power) can be run to the battery and the red switched power controls the on/off of the deck and should not provide power to anything else.