General Car Audio FAQs

Yeah, I don't think that it has anything to do with RF noise from the window motor or the headlamps themselves but rather the strain on the electrical system when something like that is used. My old prelude had the whine and there was pretty much nothing I could do about it. Opening the sunroof would make it louder too and that motor wasn't near anything audio related at all.

 

Got it. I've never seen that kind of effect before, but I've also never upgraded the audio system in a vehicle without a heavy-duty alternator.

I kinda got focused on the inductive/EM/RFI noise idea since that's the reason for physically separating wires, if the issue is taxing the charging system then it wouldn't much matter how the wires are routed.

 

I'm reading a lot about noisy cables & wires in the forums lately. One technique that works quite often is braiding the signal wires. Kimber Kable did this with their line of home theatre speaker cables. Power companies do the same thing. If you've ever driven a long distance with high tension power lines paralleling the highway, say Las Vegas to Los Angeles, you've noticed that every once-in-awhile the power line at the top of the tower drops/crosses over and switches places with the other lines. The power lines weave themselves all the way from the dam, across the desert, through substations, and on to their final destination. If you happen to live near a substation, notice that the power lines into the substation cross over somewhere and leave in a different orientation. They're braided.

Even though those power lines from the dam typically carry 385,000 volts (or more), they also act like antennas. The world is full of spurious electrical noise. Just like the power lines traveling hundreds of miles, some of those electromagnetic signals find their way into your audio cables. That noise rides along with the intended signal and gets amplified by the audio system. By interweaving/braiding the power lines with the neutral line, you reverse the amplitude of the noise signal and it cancels itself out, leaving a clean signal at the audio amplifier.

With that in mind, the reality is that in some car audio installations, you have no choice but to run all the cables together. I'm with ya wanting to make the installation clean and neat. Consider interlacing the audio cables with each other a couple of places. You may be insuring a better sound.

Granted, it's not always this simple, but you have nothing to loose by trying it. Alternator "pop" is a different problem and usually doesn't clear up by braiding the signal cables.

Anyway, I've learned a lot about all the mods I can do for my '06 4x4...my turn to contribute.

 

So if I am reading this correctly, when running my amp power cable, and my speaker wire, and my rca cables to their respective places I dont have to seperate them? I can run them all down 1 side of the car with no interference? I dont have to run lets say, the power cable to battery down the drivers side and the rca's down the passenger side, I can run all of the wires down the drivers....?

 

Yes. The only cable I have on the passenger side is for the passenger speakers.

 

So why on every diagram I have ever seen does it say to run power cable as far away from speaker/rca's as possible...just myth? If so that's a huge myth and I am writing mythbusters right now. If this is true I am so much happier about having to hook my sub up!

 

Possibly a habit developed by system designers who work with both home theater and car audio applications. For systems powered by wall outlets, it's important to separate the signal and power cables since 120V A/C can produce inductive interference (aka the "60Hz hum") by mere proximity.

According to physics, it's not possible for a 12V DC power cable to produce inductive noise in nearby wires, so there's no need to separate car audio power lines from other lines. Most HU's have separate harnesses for power and speaker wires, but that's most likely a product of most off-the-shelf connectors not being designed to handle different wire gauges since the power leads are generally much heavier wire than the signal leads (and that there's no need for rca harnesses).

If you can handle the extra $$, it's still a good idea to use coax or shielded RCA wires for a multichannel amp since there are other sources of RF interference within a car engine (the firewall should provide decent shielding in most cases, but it's not perfect).

For wiring a up a truck system, I'd tend to think that most of the signal wiring would be routed inside the cab anyway since the amp power is the only line that absolutely needs to get to the engine comparment and there's no trunk to put the amp in. On the last aftermarket system I had (in a '97 Taco x-cab), the amp was under the driver's seat and the sub was right behind with about 6" of speaker wire in between and the RCAs from the HU routed under the carpet along the center console.

 

I have seen amp owners manuals from very "reputable" companies that still tell you to not run wires together (one actually said all wires need to be crossed in a "t" fashion ) In any case as mentioned yes it is a myth that was probably carried over from home audio along with many others. Also, twisted cables offer the best noise rejection (some shielded cables can actually pick up noise in the shielding) however in a pinch I have used those "basic" interconnects found at auto parts stores etc wrapped up with the power/speaker wire and not had any noise issues caused by the wire.

 

I concur. I too believe the suggestion to separate power cables from audio cables in a mobile system comes from home theatre. You do want to get the 110 volt AC power cords from the receiver/power amp as far away as possible from the audio cables, even if the RCA and speaker cables are shielded in a home system.

Hearing alternator whine and spark plug "pop" is usually only a problem in older vehicles. Cleaning the ground paths and adding a filter to the alternator output solves the annoying background sounds.

 

Howzit guys. I have a factory tape/radio/cd in my 00 and it wouldn't turn on this morn. i tried changing the fuse and that did not work. im not at all good with car electrical and need some help please. Thanks!!

 

I'ts probably just perfect time for something better.

 

im actually quite happy with my stock stereo. any advice on why its not turning on?

 

It's 10 years old, these things happen

 

Is there a detrement to any of the factory items by installing an aftermarket head unit?
My old eclipse would lose part of the center consul clock display abilitys by changeing the headunit.

 

Usually, you won't be able to recover some of the functionality of the steering wheel controls. I say usually because some of the Eclipse head units are plug and play, and I'm not sure if it retains all usage or not.

I suspect a wiring problem. My clock works fine.

 

Clock still functions but the radio displays (you don't need anymore anyways) no longer display and I kinda miss them being up high in the pod..

Good to know about the eclipse headunits useing some of the controls though....what controls usuly get lost in the upgrade?

 

I'm having a hard time deciphering your first sentence. I'm guessing you said that now the clock works, but the radio display is dead. I don't know what you mean by 'high in the pod' because the 1st gens had the clock behind your right hand with the radio down low, mid-late 80s had no clock and the radio was still fairly low, and I don't remember a clock in the early 80s...


OH

you meant Eclipse car, not an Eclipse head unit. When I said Eclipse before, I meant this

I'm willing to bet you lose the bluetooth buttons

For me, there is a choice of the up/down control being able to change radio presets, or be able to skip tracks, but no longer both - you have to program the steering controls to do one or the other.

 

yea i was refering to the clock position in a mitsu eclipse (it's a 2000 and all radio information is in the pod that is top center of dash)


are the eclipse head units the only ones that MIGHT maintain the remote controls on the wheel?

 

I'm 90% certain

 

going further with this, there are usually only 3 noise issues to consider when upgrading the audio system:

(1) is the classic whine from the alternator. This is easy to detect because the pitch of the unwanted signal goes up with increased RPM.

(2) "pop" from spark plugs. This popping sound is like the alternator whine in that the popping speeds up as RPM increases.

(3) noise from other cables and wires in the vehicle running parallel to the audio cables.

Many vehicles 2000 model year and up are noise free because there is no distributor, no external high voltage spark plug cables, and no alternator noise because of suppression built into the alternator and vehicle wiring.

The best results for your audio upgrade will come from keeping low voltage signal lines separated from heavy current power cables & vehicle CPU data/signal lines. Some parallel routing is unavoidable, but you can cross cables at right angles with no problems. I'm running the Alpine PDX-5 power amp w/ the Alpine CDA-117 receiver, and 60 amp power cables coming straight off the battery. I have dead quiet low level signals no matter what the source. No alternator whine, no spark plug popping, and no stray induced noise from parallel cables running along side the speaker wires or RCA preamp cables. I used 9-foot twisted pair RCA cables for all the preamp signals...no unwanted noise at all.