Wiring 4 Channel Amp to Mids/Highs - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 29 (permalink) Old 04-24-2012, 07:27 AM Thread Starter
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Wiring 4 Channel Amp to Mids/Highs

I see this repeated frequently on the forum, so I decided to write up an how-to on the easiest way to wire the 4 factory location speakers (Mids/Highs) in your cobalt to a 4 channel amplifier

I worked as a car audio installer for over 14 years, and have done this method more times than I can count, with amplifiers up to 500 watts/channel with no problems, although I'm sure I will get the usual "but the wire is not heavy enough for the amplifier power" arguement. Use your own judgement, but I can tell you from experence, that it is not a problem. After all, look at the tinsel leads on the speaker, they are usually 18ga or smaller, if they can handle the power, so can the factory wiring.

this will of course, also work with the factory speakers as well, but a high powered amp will likely destroy the cheap factory speakers, so a speaker replacement is recommended

this method will not work with the factory amplified systems, you will have to wire to the front speakers themselves (or to the amplifier location, which is under the steering wheel, I think it would be just as easy to wire to the speakers themselves)

If you are not sure if you have the factory amplifier, here are some tips:

do you have the factory sub...well then you have the factory amplifier....

when you pull out the radio...plug in the adapter harness before making the modification below, get any one of the speaker leads...say the Gray (+) Gray/black (-) Right front lead, and touch the wires + and - to a 9 volt battery...if the speaker makes a pop sound, you do not have a factory amplified system, and this method will work for you

Step 1:

remove your radio of course, this method works with an aftermarket radio, but will also work if you use the factory radio, and cut the speaker leads and wire a line output converter to the radio side for the RCA output to the amplifier

on the adapter harness, you will have the ( 8 ) speaker input leads

Gray (+) Gray/black (-) Right front
White (+) White/black (-) Left front
Violet (+) Violet/black (-) Right Rear
Green (+) Green/Black (-) Left Rear

connect the wires as follows:

Gray (+) to Violet (+)
Gray/Black (-) to Violet/Black (-)
White (+) to Green (+)
White/Black (-) to Green/Black (-)


the end result should look something like this:



I have pictured a PAC audio C2R-GM11

of course, you would heatshrink, tape, or otherwise insulate these wires

you have now created a circuit in which your rear speaker leads are connected directly to the front speaker leads that are already running throughout the car (do you get where I am going now?)

you would not connect the speaker outputs from the radio, isolate those wires to keep them from touching each other or grounding out

Run a single conductor wire (usually at least 16ga) from the amp turn on lead of your radio (usually dark blue) or if you still have a factory radio, find the power antenna lead (some will also tie to an accessory fuse in the fuse box)

run the RCA cables and the remote turn on wire into the trunk

Mount your 4 channel amplifier somewhere in the trunk of your car... I put mine right on the rear deck



Run the power wire with fuse directly from the + terminal of your battery in the trunk

Run the ground cable from your amplifier to a bolt on the chassis, but be sure to clean off all paint where the eyelet will mount to the chassis for a good ground connection

connect the previously run remote turn on wire to the remote lead on the amplfier, and connect the RCA's to the input of the amplifier

Remove the speaker leads from the rear speakers, you can then either cut the connector, or use an adapter harness such as this:

Metra Part # 72-4568 | GM wire harness | Metra Online

Connect the body side of the rear speaker wires to the front leads of the amplifier, the left rear connection is now the left front, right rear is now right front

Connect the rear output leads from your amplifier directly to the rear speakers

start the car, turn on the radio, and adjust the gain controls of the amplifier

***I say to start the car for a couple reasons, firstly, if you have engine noise through the speakers when the car is running, it can be removed many times by turning down the gains on the amplifier, if this does not eliminate it, check your ground wire on your amplifier, a bad ground will often show itself with amp noise, if these fixes do not work, try a ground loop isolator, such as this:

http://www.amazon.com/4-Channel-Ground-Loop-Isolator/dp/B004C4ZNNO/ref=sr_1_1?ie=UTF8&qid=1335277494&sr=8-1
also, this can take quite a while to get the sound right where you want it, if the car is running, you won't kill the battery, but be sure whereever you are doing this is well ventilated from exhaust gasses

re-install the radio, and enjoy having much cleaner, louder mids and highs!

John
2008 Cobalt LT
SS springs and Stagg struts
Pioneer AVIC-X930BT GPS
Memphis 16-MCH600 "Baby Belle" hybrid amplifier
MB quart Premium 6.5" componant/premium tweeters front
MB quart Premium 5.25 componant/premium tweeters rear
Memphis PR-10" sub in factory sub box

miles and miles of dynamat extreme...

Last edited by jignaczak; 04-26-2012 at 11:26 AM. Reason: adding additional information
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post #2 of 29 (permalink) Old 04-24-2012, 08:19 AM
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Never thought of this. I still say speed cable though
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post #3 of 29 (permalink) Old 04-24-2012, 08:34 AM
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Im not following you on combining the front and rear connections behind the deck. Whats the purpose of this?
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post #4 of 29 (permalink) Old 04-24-2012, 09:23 AM Thread Starter
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by combining them, you would just use the wiring that is already in the car, and use the rear speaker leads to connect to the amplifier for your front speakers

---------- Post added at 12:23 PM ---------- Previous post was at 11:44 AM ----------

I don't see the advantage to speed cable...

you would be wiring all 4 speaker locations, running them 20 feet to the front of the car, and then running them to their final locations

this way, you are just running to the front speakers, and then connecting directly to the rears

John
2008 Cobalt LT
SS springs and Stagg struts
Pioneer AVIC-X930BT GPS
Memphis 16-MCH600 "Baby Belle" hybrid amplifier
MB quart Premium 6.5" componant/premium tweeters front
MB quart Premium 5.25 componant/premium tweeters rear
Memphis PR-10" sub in factory sub box

miles and miles of dynamat extreme...

Last edited by jignaczak; 04-25-2012 at 08:22 AM.
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post #5 of 29 (permalink) Old 04-24-2012, 11:55 AM
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Quote:
Originally Posted by jignaczak View Post
by combining them, you would just use the wiring that is already in the car, and use the rear speaker leads to connect to the amplifier for your front speakers
No I get that, saves running 2 new sets of speaker wire to the back, but why are you mixing the front and rear speaker lines at the deck?

Rear speakers you dont touch as the wires and amp are right in the trunk already, fronts can go from the front outputs at the deck to the rear speaker lines at the OEM harness, then cut at the rear speakers and that wire run into the front out at the amp, turning the rear OEM speaker line into amp'd front speaker line.

But you have the front and rear speakers lines twisted together at the deck harness for some reason and thats whats not making sense to me....you dont use the deck speaker output wires at all when using an amp, so what are they doing?
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post #6 of 29 (permalink) Old 04-24-2012, 12:07 PM Thread Starter
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I'm not twisting anything at the deck itself, those wires you see in the pic are for the harness into the car

the wires coming off of the deck are isolated, and left unconnected

John
2008 Cobalt LT
SS springs and Stagg struts
Pioneer AVIC-X930BT GPS
Memphis 16-MCH600 "Baby Belle" hybrid amplifier
MB quart Premium 6.5" componant/premium tweeters front
MB quart Premium 5.25 componant/premium tweeters rear
Memphis PR-10" sub in factory sub box

miles and miles of dynamat extreme...
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post #7 of 29 (permalink) Old 04-24-2012, 05:15 PM
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Quote:
Originally Posted by jignaczak View Post
I'm not twisting anything at the deck itself, those wires you see in the pic are for the harness into the car

the wires coming off of the deck are isolated, and left unconnected
gotcha, makes way more sense now. I thought you were going to connect them to the deck like that for some reason. now I see its just the junction of the rear speaker wire going to the front speaker wire.
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post #8 of 29 (permalink) Old 04-25-2012, 07:32 PM
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Hmm..

Combining the front and back now actually makes your 4 channel to unit a 2 channel unit, your fade option will be useless. For instance, if you had an after market DVD player unit, and it had surround, which many DVDs do, anything that was supposed to be heard from the rear speakers would be heard from the front also (and vice-versa), thus sacrificing your surround. (Some music also has 4 channels + so this would ruin a surround sound experience.

Many would not notice, probably not care either, but if that was done on my car, I would be wanting my 4 channels back.

I understand what your trying to do, the proper way would be to run separate wires from each of the 4 channels, then add some blocking diodes "before" reducing to 2 channels to support a 2 channel amp. (this way you get your 4 channels in speakers and your highs and lows for the amp)

If you have an aftermarket unit, just use the pre-outs 99% of them come with.

Old Car: Chevy Cobalt 2006 LS Sedan base (Automatic)

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Last edited by johnccc; 04-25-2012 at 07:42 PM.
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post #9 of 29 (permalink) Old 04-25-2012, 07:56 PM
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Johnccc, you didn't get it, he's just using the original rear speaker wires for the output feed for the front door speakers to avoid running these 4 wires. I presume the amp is a 4 channel just the same with sub out.

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post #10 of 29 (permalink) Old 04-25-2012, 08:07 PM
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Quote:
Gray (+) Gray/black (-) Right front
White (+) White/black (-) Left front
Violet (+) Violet/black (-) Right Rear
Green (+) Green/Black (-) Left Rear

connect the wires as follows:

Gray (+) to Violet (+)
Gray/Black (-) to Violet/Black (-)
White (+) to Green (+)
White/Black (-) to Green/Black (-)
So...

Right front to Right Rear (those 2 channels become one now, "Right")

Left front to Left Rear (those 2 channels become one now, "Left")

We are only left with 2 channels, left and right, commonly known as "stereo".



According to his instructions he has joined the rear and front channels.

Each channel requires 1 ground and 1 positive, so for a 4 channel situation, you will need 8 outlets, I only see 4.

This would work for the amp, but would result in the rest of the system only getting 2 channels, wouldn't it?

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Last edited by johnccc; 04-25-2012 at 08:13 PM.
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