Engine noise

I have a slight amount of engine noise coming through my speakers. My installer added one of those inground isolators but it still persists. I have a 09 Tacoma dbl cab. The head unit is the Kenwood DNX 8120 with Alpine SPS-600C speakers in the front and I think SPS-609 in the back doors. There is also a Bazooka 8" sub in the back with a 5 channel amp. I know that all the speaker wires are ran in one side and the power cable runs on the other side with the exception of one rca cable running paralle with the power. Other people tell me that there should not be any noise and even the use of the isolators is just a band-aid. The ground for the amp is grounded through the bolt on the back seat.

Any help would be great..

Thanks

 

Does the noise persist on all inputs (radio, CD, iPod, etc)?

Does the noise change pitch insync with the RPM of the engine?

Those two questions will help pinpoint the cause. A ground loop isolator is a band-aid in a truck application, IMO. You should have access to an adequate grounding point. You should check that the ground that you have is to bare metal. If it isn't, scrape all the paint and primer from the immediate area so that you have good metal to metal connection. You may also try and move the ground from that point to another bolt that is connected to a more solid portion of the body of the truck.

If it is only coming from one of the input sources, then that would lead me to believe that the problem is with that source or its connection. Sometimes there are faulty cables or the connection can be loose. Check to make sure it isn't something simple like that.

 

Thank you.

Yes, the noise comes from all sources. It does not matter. I can have the radio set to DVD with no DVD in it but it will still have the same noise. And yes the noise changes with the change of RPM'S.

What other soild portion of the truck? The bolt used for the back seat seems very solid. I thinking there probably is paint/primer inderneath the foot of the seat.
The 8120 takes a second to boot up and the noise goes the all speakers before the 8120 boots up completly.
I also read somewhere that the ground from the wireharness should be going to a seperate baremetal location as apposed to the one used in the harness itself. I dont know.... but thank you.

 

You might want to try moving the rca away from the power wire. I know they have a tendancy of picking up engine noises. Try and keep all the rca's and speaker wires away from power wires.

 

Before you waste your time doing this, let me assure you that this is a myth and is not true. I think sooner has nailed this one right on.
1- Always check your ground wires. For your amp and the HU
2- check your speaker/input connections.

 

Waste of time. They (RCA cables and speaker wires) don't have a tendency of picking up engine noise through the power wires.

 

Thanks for the advice, it allowed me to talk to the owner/installer with information I would not have had otherwise. The owner was very accommodating and assuring. It has been 2 days and I am very pleased. They stepped up and took care of the engine noise with no filters. They shortened the ground on the amp. Something to do with the ground and the battery, and instead of using the ground in the radio harness they separated the ground from the harness and grounded to the metal. Who knows what else, at least that what they told me. All I know is the noise is gone and the system rocks.

I am bummed I went with an 8'" Bazooka sub. I owner sold me that because I told him I didn’t want to do anything to the back of my truck, I feel he sold me what I asked for but now I see that the bazooka is the weakest part and will be getting that fixed soon.... Live and learn. I think the cost of the truck was the cheapest part...haha.


Thanks again

 

So after they ended up proving to me that the system can be installed without engine I upgraded the components. I added 2 Memphis 10” subs 15-SC10D4 upgraded the amp from a 16-MC5.700 to a 16-MC5.1400 and the front speakers (15-MCC6) as well. It is all Memphis parts.

The system really really kicks ass except now I have a slight amount of engine noise. The head unit that is in it now is the Kenwood DNX 8120. When the DNX 9140 comes out I am having that put in there.

So for now I have to live with a slight amount of noise. It just sucks because you guys helped me point out some things to the installer that helped get my original problem fixed. Now I don’t know what else to bring up as to why the noise is back. Is there a chance that the new unit will fix the noise?

Thanks again..

 

The problem could be back due to sloppy work when they reinstalled your equipment and the new equipment. I'd check the ground for the amps again, to make sure they are securely attached to the body. I'd also check again that the noise present from all sources.

 

I was kinda was wondering that. The difference is that this time it only happens when I am driving. Actually when I accelerate. And it is very faint. Where as before it was all the time. But I like the ground idea. Do you think it sould be a thicker ground wire?

thanks

 

It should be the same size as the main power wire. I typically use 4awg wire.

 

Ok Ill look, but I am pretty sure it is smaller.
Thanks Ill take a look at let you know...

Dave

 

hey, fyi i have been installing stereos for about 20 years now.
a couple things i would mention, the reason you get engine noise in the first place is because the input impeadance of the amp and the output of the HU dont match, often times a difference in reference ground can cause this, so as long as you have the HU and the amp grounded to the same location there shouldnt be any noise. unfortunatly because the HU is mounted in the dash and in all likelyhood bolted to the dash which is metal, the entire radio is grounded at the dash. since you cannot change this you might be better off having them ground the amp at the dash, i would try grounding it under one of the bolts that holds the HU in the dash.

next the issue is most common when you have a "tweek happy installer" many installers think turning up the gains ssounds better, i have the exact same HU as you and i know its a 4 volt pre out. 4 volts is plenty of juice for a signal. if you cannot turn your head unit past 70% on the volume dial without getting distortion from your amps your gains are way too high. try turning all the gains down a touch. you should be at near 90% max volume before you reach the celing of the systems max volume.

if you do these things i guarentee you 100% the noise will be gone.

and to the other poster, yes running your rca's alongside the power cable is a myth in todays modern stereos, back in the day there was some truth to it but i have done countless systems taping the rca's and power as well as speakers all together and had noise free installs.

there are some cars where a ground loop isolator is just easier, yea its a bandaid, but it works and i have not noticed any signal degradation. back when i installed for a living you wouldnt get much respect by using them but now that i dont give 2 shits about what people think i will use one whenever i dont feel like chasing engine whine down.

also i wanted to add a couple things, dont let stereo shops sucker you into buying expensive rca's! having a degree in electronics and 20 years installation trust me when i say that oxygen free, twisted pair, triple shielded cables do nothing for you!! ive seen just as many engine noise producting installs with the highest quality signal cable as i have seen noise free installs with rca's i bought from wallmart!

don't believe the wire myths either, you dont need 4 gauge to run a system like yours 8 gauge is perfect! 10 gauge might be pushing it a little. bottom line is that the voltage drop is not nearly what they tell you because the amps dont draw nearly what they say they will. i have installed plenty of the big systems and a 30 amp fuse wont blow in 90% of the installs out there. a typical 5 channel amp might draw 25 amps on a good day! that said, 8 gauge is more than enough even if your running 25 feet of it. most amps are regulated internally anyway so if there is a slight drop in voltage it wont affect anything.

HOWEVER, if you have one of thoes fancy JL audio slash amps they are power mongers! best to go with the manufacturers reccommendations on thoes amps. they have a very stiffly regulated power supplies and will get hotter if they dont get the full voltage. when a regulated amp has a voltage drop it will draw more current to make up for it which also lowers the voltage, which draws more current, you get the idea. so you need a good power wire on thoes amps. but i wouldnt worry about it unless your talking some of their larger wattage units.

i could go on, one of the things i hate about car audio is what i like to call RICE CAR AUDIO what i mean to say is that people buy audio with their EYES and not with their EARS! they wont buy a sub unless it has BIG magnets on it they wont buy speakers unless they look meaty!
if you understand the fundamentals about how speakers work and how the magnetic field reacts against the coil and the damping effects it has you can actually have too much magnet, also once the tyoke and gap plate of the soft carbon steel of the motor assembly of the subwoofer are fully saturated in a magnetic field adding a bigger magnet will have zero effect on the motor assembly of the speaker.
in fact rare earth magnets like neodimimum magnets are about 11 times more powerfull than the typical ceramic magnets. you could use much smaller rare earth magnets and could make a subwoofer weigh a fraction of what they do but no one would buy them unless they have a big magnet on the back!

if people only knew 1/2 of what i know about this industry they would puke on themselves if they knew where everything is actually made and what it costs.

just for fun, ill share this.. many years ago when i was at the height of my caraudio carrear i had a business called RMS caraudio "Rocky Mountain Subwoofers" i contacted a chienese manufacturer to see what it would cost to produce my own line of components.
in case you don't know, components are usually a 6.5 inch woofer, a crossover and a tweeter that all get mounted separatly in each door. so if you buy a set you get 2 woofers, 2 xovers and 2 tweeters.
these usually cost about 200-400 dollars retail!

now keep in mind i was looking for high end speakers, this means i was going to use full cast aluminum baskets, neo tweeters and adjustable crossovers. these units would include speaker grills, wires and the packaging with my company logo on it
my cost, drumroll please.... $26.00 per set! the only problem is that you have to buy an entire container of them to get that pricing. you know what a container is? its essentially a truckload, the things they ship from china on a cargo ship! you can buy smaller quantities for maybe 50 a set for a few thousand sets.

but the point is at 26.00 a set and sold retail for about 400 bucks! its almost like selling cocaine! now you know why caraudio is big business! and the fact is 95% of all the name brands you see in stores came in fact from very likely the exact same assembly plant in china! the only difference is each brands marketing design which are patented or trade marked. a speaker is nothing more than a diaphram that moves air! i pick speakers that fit the space im trying to install it into. i will not buy a big ass gaudy looking speaker and hack up a door panel to get it in there just because it LOOKS like a good speaker!

if anyone would like to get an honest opinion about what to buy and what to look for to save a little money and get a great sounding system feel free to message me and i will happily make a reccomendation.
having someone who doesnt sell car audio for a living but knows the inside scoop and has a strong background in electronics and the 12 volt industry can save you a lot of time and money. ill give it to you straight! and i can tell you where to buy to get the best deal.

 

i got dibs on the old deck

 

wow, great writeup bass mechanic! thanks for the tips!!

 

wow bass mechanix can I come to you if i have questions in electrical theory class

 

absolutly, its been a few years but i still know my formulas lol

heres a quiz for ya, and dont go looking it up online, what is a mosfet transistor, what does MOSFET stand for?
dont cheat!

here is another, which is the best conductor and the worst and in what order between the following.
between

gold
copper
silver
aluminum

and tell me why

 

Excellent information there bass mechanic some of which I've previously posted in the FAQ THREAD HERE and feel free to add to it if you'd like.

 

I forget what mosfet stands for... metal oxide something field effect transformer... it takes the dc current and changes it to ac current for the signal to pass along greater power to the speaker... or something like that.

silver, copper, gold aluminum. It has to do with valence electrons. Silver isn't used due to it being very expensive and it corrodes very easily, gold isn't used due to expense, but is great for plating exposed connections due to its extreme lack of corrosion. Aluminum isn't as good as copper but it is usually cheaper. Copper is the best choice for most wiring needs due to how it just sits in a happy place where it is better than average at everything. All thanks to those valance electrons.

 

sooner gets 10 points! yeay! most people think gold is the best conductor, it actually isnt that good, they use it because it doesnt corrode or oxidize. aluminum is used im power lines because its cheap. and more importantly light weight! when they run miles of it across the country it takes a lot fewer poles to support it, and because its usually about 60,000 volts and about 40 amps it doesnt have to be the best conductor. the step down transformers at your home provide the needed amps and a lower voltage its really a neat system!

MOSFET metal oxide silicon feild effect transistor
its a high impeadance transistor whos metal oxide mated to the silicon makes a small capacitor these transistors make excellent high speed switches and are primarly used for powersupples in caraudio amps. a bank of them and a square wave generator make a very efficient powersupply using a transformer. the AC output is rectified back to DC and regulated to be used to power the output transistors in an amplifier.