Wiring through the firewall for car amp

[Daryl80]

Hi All,

I've done a search on this, but can't find the answer to my question.

I'm currently in the process of upgrading my car stereo, replacing HU, adding an amp etc, and am in the process of putting the amp in. Now I understand that the only way of getting the wires through, is through the firewall on the passenger side, then through the trunk wall on the drivers side. However, what that has meant is of course, both RCA's and speakers are sitting pretty much either behind or infront of the battery.

Not only that given that I need to run a power and ground wire into the trunk from the battery, I also need to use the same trunk hole as the speakers/ RCA's to wire the power cables through.

Now, my concern of course is with engine and more so alternator whine by not insulating the cables correctly. I know that interference can be caused due to the fact that power is too close to the audio signal cables. Combined by the fact that the RCA's and speakers cables need to go over the battery, I'm just worried that all I will hear is the alternator through my stereo.

As such, is there any way to separate the proximity of the speaker cables/ RCA's with any of the power cables or batteries.

The diagram shows in solid lines where the cables are now. The dotted line is where I would ideally like the cables to be routed.

Is this at all possible? I really haven't done any exploritory surgery of the car trunk, to see if this is feasible or not. I see that the trunk walls have carpeted on the side, so I'm think something must be possible.

Keen to hear your thoughts.

What has been other people's experience in wiring amps/ speakers etc. Am I being overly cautious. I just have had several bad experiences where alternator whine, has ruined a perfectly good system.

And finally, I am using good quality RCA's and speakers, and have paid a premium for it. I just want to make sure I'm doing all I can to remove any unwanted noise.

Thanks!

Daryl

[JeTexas]

I don't know if proximity is the real factor or if it just comes from not using correctly shielded cables. Supposedly with speaker wire you don't have to use shielded cable because it's a high-power signal -- obviously this isn't true because the aux-in cables in my car sure pick up a ton of alternator whine.

I would say spent the extra money to use all shielded cable and don't splice any connections because by splicing the wires together, you've just opened up the shielding. Instead, make all connections using shielded plugs.

There are also ground loop isolators that you can run inline which will filter out the engine/alternator noise.

Edited July 8, 2008 by JeTexas

[Ross1]

Hi All,

I've done a search on this, but can't find the answer to my question.

I'm currently in the process of upgrading my car stereo, replacing HU, adding an amp etc, and am in the process of putting the amp in. Now I understand that the only way of getting the wires through, is through the firewall on the passenger side, then through the trunk wall on the drivers side. However, what that has meant is of course, both RCA's and speakers are sitting pretty much either behind or infront of the battery.

Not only that given that I need to run a power and ground wire into the trunk from the battery, I also need to use the same trunk hole as the speakers/ RCA's to wire the power cables through.

Now, my concern of course is with engine and more so alternator whine by not insulating the cables correctly. I know that interference can be caused due to the fact that power is too close to the audio signal cables. Combined by the fact that the RCA's and speakers cables need to go over the battery, I'm just worried that all I will hear is the alternator through my stereo.

As such, is there any way to separate the proximity of the speaker cables/ RCA's with any of the power cables or batteries.

The diagram shows in solid lines where the cables are now. The dotted line is where I would ideally like the cables to be routed.

Is this at all possible? I really haven't done any exploritory surgery of the car trunk, to see if this is feasible or not. I see that the trunk walls have carpeted on the side, so I'm think something must be possible.

Keen to hear your thoughts.

What has been other people's experience in wiring amps/ speakers etc. Am I being overly cautious. I just have had several bad experiences where alternator whine, has ruined a perfectly good system.

And finally, I am using good quality RCA's and speakers, and have paid a premium for it. I just want to make sure I'm doing all I can to remove any unwanted noise.

Thanks!

Daryl

You indicate that you already have it wired to go pass the battery. Turn it on and see what happens! If you have wired it correctly and if indeed you have used high quality wiring, there may be no problem! The biggest causes of background noise is a ground loop or low quality wiring! If your power, RCAs, and speaker wire are high quality, you shouldn't have a problem!

[juniinc]

Yes even with a pair of high quality RCA cable, ground interface can be caused.

My problem was when I tie wrapped all the wires (using the best quality Phoenix Gold RCA)

from the head unit, make sure to seperate the RCA cable,no cable looping,

best way to eliminate the G loop is throwing a ground loop isolator,

I see the diagram U've posted,,, my cables were atually routed on the side U prefer( but no idea if its opposite on LHD car)

Hi All,

I've done a search on this, but can't find the answer to my question.

I'm currently in the process of upgrading my car stereo, replacing HU, adding an amp etc, and am in the process of putting the amp in. Now I understand that the only way of getting the wires through, is through the firewall on the passenger side, then through the trunk wall on the drivers side. However, what that has meant is of course, both RCA's and speakers are sitting pretty much either behind or infront of the battery.

Not only that given that I need to run a power and ground wire into the trunk from the battery, I also need to use the same trunk hole as the speakers/ RCA's to wire the power cables through.

Now, my concern of course is with engine and more so alternator whine by not insulating the cables correctly. I know that interference can be caused due to the fact that power is too close to the audio signal cables. Combined by the fact that the RCA's and speakers cables need to go over the battery, I'm just worried that all I will hear is the alternator through my stereo.

As such, is there any way to separate the proximity of the speaker cables/ RCA's with any of the power cables or batteries.

The diagram shows in solid lines where the cables are now. The dotted line is where I would ideally like the cables to be routed.

Is this at all possible? I really haven't done any exploritory surgery of the car trunk, to see if this is feasible or not. I see that the trunk walls have carpeted on the side, so I'm think something must be possible.

Keen to hear your thoughts.

What has been other people's experience in wiring amps/ speakers etc. Am I being overly cautious. I just have had several bad experiences where alternator whine, has ruined a perfectly good system.

And finally, I am using good quality RCA's and speakers, and have paid a premium for it. I just want to make sure I'm doing all I can to remove any unwanted noise.

Thanks!

Daryl

[Daryl80]

Hi all, thank you for your prompt reply. I do take your points on board, but I just have a few question for some individual responses here.

JeTexas, may I ask what is a ground loop insulator, and what causes a ground loop. I've done a wiki search on it, but dont really get it. If I try this out and still get noise, maybe I will get one of these

juniinc, thanks for your response also. Your amp placement is exactly what I'm looking to do also. I think for me, my master brake cylinder is on the right hand side, so I think thats why the holes in the FW are flipped. But can you just confirm, that means, you still had to wire your power cables, and your RCA's/ speaker cables through the one trunk hole. I guess this is what i wanted to avoid.

Oh, and one last question juniinc, how did you mount your amp. It looks like its on an angle. Looks great, just keen to get some mounting tips on how i can secure it down.

Thanks again to all who reply.

[JeTexas]

It's basically a filter for the hum.

To quote from http://www.epanorama.net/documents/groundloop/

Ground loop is a condition where an unintended connection to ground is made through an interfering electrical conductor. Generally ground loop connection exists when an electrical system is connected through more than one way to the electrical ground.

When two or more devices are connected to a common ground through different paths, a ground loop occurs. Currents flow through these multiple paths and develop voltages which can cause damage, noise or 50Hz/60Hz hum in audio or video equipment. To prevent ground loops, all signal grounds need to go to one common point and when two grounding points cannot be avoided, one side must isolate the signal and grounds from the other.

You can see one in juniinc's photo.

Here's an example.

http://www.radioshack.com/product/index.js...rentPage=search

Hi all, thank you for your prompt reply. I do take your points on board, but I just have a few question for some individual responses here.

JeTexas, may I ask what is a ground loop insulator, and what causes a ground loop. I've done a wiki search on it, but dont really get it. If I try this out and still get noise, maybe I will get one of these

juniinc, thanks for your response also. Your amp placement is exactly what I'm looking to do also. I think for me, my master brake cylinder is on the right hand side, so I think thats why the holes in the FW are flipped. But can you just confirm, that means, you still had to wire your power cables, and your RCA's/ speaker cables through the one trunk hole. I guess this is what i wanted to avoid.

Oh, and one last question juniinc, how did you mount your amp. It looks like its on an angle. Looks great, just keen to get some mounting tips on how i can secure it down.

Thanks again to all who reply.

[atmorris]

Interesting discussion. My amp is also mounted in the same location. My interconnects (RCA's) come through the firewall via the opening just to the right of the steering column, across in front of the battery tray, and through the opening in the passenger side of the trunk wall below the sealing gasket. I do not use a ground loop insulator. I do not have any static or noise in my output. I just used good quality, twisted pair, gold plated, interconnects.

Edited July 9, 2008 by Andy_M

[Ross1]

Interesting discussion. My amp is also mounted in the same location. My interconnects (RCA's) come through the firewall via the opening just to the right of the steering column, across in front of the battery tray, and through the opening in the passenger side of the trunk wall below the sealing gasket. I do not use a ground loop insulator. I do not have any static or noise in my output. I just used good quality, twisted pair, gold plated, interconnects.

A ground loop isolator is a bandaid for an incorrect installation! All it is doing is trying to filter out extraneous noise. I have never used one, but I doubt that it filters out everything and possibly filters out some of the music! I stick to my previous comment that eliminating the ground loop and using high quality wiring and you won't have a problem!

[juniinc]

Anytime & thanks for the compliment.

yes, but I ended up drilling 2 holes on the rubber plug. I spliced some existing speaker wires so they didn't have to go through the hole.

There are 2 sheet metal brackets(angled) on the back side, then they were secured with a couple of 1/4" bolt & nuts.

Hi all, thank you for your prompt reply. I do take your points on board, but I just have a few question for some individual responses here.

JeTexas, may I ask what is a ground loop insulator, and what causes a ground loop. I've done a wiki search on it, but dont really get it. If I try this out and still get noise, maybe I will get one of these

juniinc, thanks for your response also. Your amp placement is exactly what I'm looking to do also. I think for me, my master brake cylinder is on the right hand side, so I think thats why the holes in the FW are flipped. But can you just confirm, that means, you still had to wire your power cables, and your RCA's/ speaker cables through the one trunk hole. I guess this is what i wanted to avoid.

Oh, and one last question juniinc, how did you mount your amp. It looks like its on an angle. Looks great, just keen to get some mounting tips on how i can secure it down.

Thanks again to all who reply.

Edited July 10, 2008 by juniinc