Connecting your car speakers to an amp: use your factory wiring (2024)

Tip: You can use your vehicle's factory wiring

Connecting your car speakers to an amp: use your factory wiring (1)

by Crutchfield's Buck Pomerantz

Connecting your car speakers to an amp: use your factory wiring (2)

Sending the audio signal from a receiverto a 4-channel amplifier's inputs via RCA cables or the amp's speaker-level inputs is straight forward and simple enough, but getting the amplified signal back to the speakers—well that's another matter.

This article discusses adding an amplifier to an aftermarket stereo. For tips on connecting an amplifier to a factory stereo, read this article instead.

Getting signal to the speakers

The speakers are usually in four different corners of your vehicle, and running separate new speaker wires to each one presents many challenges, including how to get the wire past the car door hinges to the front door speaker locations.

A convenient way to send the powered signal from your amplifier to your speakers is to run the speaker wires back to the harness behind your stereo, where all your car’s speaker connections are accessible in one place.

Which speaker wires go where?

Normally, when you install a new stereo, all the wires from the stereo would connect to the car wiring adapter. The wires would run from one black connector to the other (the right side of the photo below).

But since we're using an external amplifier for the speakers, the speaker wires from the car get diverted to the amp —that's the bundle of wires on the bottom plug heading left to the amplifier.

The speaker wires from the new stereo aren't used. You can either cut them off (like we did in the photo below) or just tape them up – each wire individually – so that none of the wire ends can touch anything else.

Meanwhile, the RCA cables carry the audio signal to the amplifier and the blue wire from the stereo turns on the amp whenever the stereo is turned on.And yes, fade and balance controls will still work fine, so long as you connect the RCA cables correctly.

Connecting your car speakers to an amp: use your factory wiring (3)

Running the amp's output wires to the speaker wires on the stereo's adapter harness is how you avoid having to run new speaker wiring throughout the car. That's the bottom side of the triangle in the photo above — speaker wires from the amp connect to the speaker wires on the adapter harness. Then that harness plugs into your car. The diagram below is a more detailed depiction of the layout.

Connecting your car speakers to an amp: use your factory wiring (4)

New speaker wires from the amp connect to the speaker wires in the stereo adapter harness

For 4-speaker systems, you'd need to make eight connections — a positive and negative wire for each speaker. This means, you just need to run the eight speaker wires from the dash to the amplifier, just like you do the RCA cables. In fact, when you're installing the amp, it's smart to run the RCA cables and new speaker wires at the same time.

Connecting your car speakers to an amp: use your factory wiring (5)

Some products to help you do it

Our favorite option is the Crutchfield9-wire cable shown above because it helps simplify running eight speaker wires plus a remote turn-on lead from your amplifier to the rear of your receiver and each set of speaker wires is color coded. We also carry a small selection of highly conductive, pure copper speaker wire, available by the foot, that will also work well, if you don't want the 9-wire, all-in-one solution.

A multi-pack of Posi-Products Car Stereo Connectors could come in handy here, so you can make all the speaker connections without having to solder anything.

High-power amps need bigger wires

For amplifiers with more than 75 watts RMS of output per channel, it may be better to go ahead and run new 14- or 16-gauge speaker wires directly from the amp to each speaker.

Factory speaker wires are very thin, with high electrical resistance, so they can cause noticeable power loss when higher wattages try to get through. But amplifiers of 75-watts or less aren't really affected by this, so running their outputs through factory wiring remains a practical and convenient solution.

Let us know what you need

This article focused on a way to simplify the speaker connections when using an aftermarket stereo. If you're connecting an amplifier to a factory system, check out this How To guide for tips. For information about other aspects of amplifier installation, like power and ground wiring, check out our Amplifier Installation Guide.

If you have any questions about connecting a new amplifier to your speakers, contact our advisors via chat or phone. They'll take the time to answer your questions and explain the details, then get you set up with whatever you need.

Comments (252)

Please share your thoughts below.

  • Felix from Jacksonville

    Posted on 6/3/2024

    I got 4 4 ohm 8" bullets and a ssl evo 3000.1 1 ohm stable how can I wire it

    Connecting your car speakers to an amp: use your factory wiring (6)

    Connecting your car speakers to an amp: use your factory wiring (7)

    Buck Pomerantz from Crutchfield

    on 6/4/2024

    Felix, Four 4-ohm speakers are usually wired together to a mono amp like this diagram.

  • Jonas from Spokane

    Posted on 10/2/2023

    I am installing a 2 amplifier application in my vehicle. One class D monoblock amplifier for my subwoofer. One class A/B amplifier for my mids and highs. My question is about wiring my mids and highs. I have six 4 ohm rated speakers of varying rms ratings and class of speakers (full range, midrange, coaxial). The amplifier is 2 channels rated for 300 watts rms at 4 ohms per channel. I am aware that I am restricted in my ability to control front/rear fade. My initial instinct is to split the class of speakers down the middle per channel 1 full range, 1 mid range, 1 coaxial wired in series parallel to match the 4 ohm rating but the combined rms rating of the speakers will be above what the amplifier can output in rms (395rms>300rms). Question 1 is this configuration ok to run on the wiring side in reference to the indifference of speakers class. Question 2 is it inherently bad to underpower these speakers in this particular configuration.Question 3 should the speaker classes be separated to separate channels. Mids on one channel and full range/coaxial on the other?

    Connecting your car speakers to an amp: use your factory wiring (8)

    Connecting your car speakers to an amp: use your factory wiring (9)

    Buck Pomerantz from Crutchfield

    on 10/2/2023

    Jonas, Three 4-ohm speakers can get wired together to form a 12-ohm, a 1.3-ohm, a 2.7-ohm, or a 6-ohm load. If your amp can handle it, you could wire two speakers together in series (one after the other) and then wire a third speaker in parallel (+ to + and - to -) to that pair to form the 2.7-ohm total load that your amp can handle on each channel. That's 3 speakers per channel on a 2-channel amp. Without knowing precisely what amp and speakers you're referring to however, we can't help you with more advice. If you want a question answered about a system, you must identify the gear by brand names and model numbers so we can get the right information to you.

  • Rocky from Sodasprings

    Posted on 9/29/2023

    I bought a Sony head head unit with 45w/RMS from you guys. I'm running my low power stock speakers though it and it works good. My question is can I and an 4-channel amp using the RCA jacks, and add 4 more speakers for a total of 8? So I want to run 4 off the head unit and 4 off the Amp simultaneously. Is this possible, or ok to do?

    Connecting your car speakers to an amp: use your factory wiring (10)

    Connecting your car speakers to an amp: use your factory wiring (11)

    Buck Pomerantz from Crutchfield

    on 9/29/2023

    Rocky, Can't imagine how that many speakers would work in your car, but in car audio application, if you can handle custom installation - anything is possible.

  • Justin

    Posted on 9/28/2023

    I have a 04 Lexus ES330 without the factory amp. My question is with a 5-channel amp would I be able to get sufficient power to all four door speakers and the 8-inch woofer in the back if I also separately ran a Monoblock to power my two twelves from my previous cars' audio set up. Would like to have each speaker receiving at least 45 watts rms

    Connecting your car speakers to an amp: use your factory wiring (12)

    Connecting your car speakers to an amp: use your factory wiring (13)

    Buck Pomerantz from Crutchfield

    on 9/29/2023

    Justin, Check out our selection of 5-channel amplifiers. If you see one you like, give us a call and talk to one of our Advisors. We can help you choose the right gear and give you the right advice on how to install it.

  • David from Cádiz, Spain

    Posted on 7/30/2023

    Hello, Buck, it´s David again (who wrote the 15th July comment). I live in Spain and it would be better if I had another way to communicate to Crutchfield team, such as e-mail, or message. Also, I have been doing a little research about it and I get an idea of the materials i need, now I would just appreciate if any proffesional could help me making sure the procedure and materials I choose are right. I also wanted to thank you and all the team because you have introduced me to this matter very well.

    Connecting your car speakers to an amp: use your factory wiring (14)

    Connecting your car speakers to an amp: use your factory wiring (15)

    Buck Pomerantz from Crutchfield

    on 7/31/2023

    David, Check out our online Car amplifier installation guide for some help. Otherwise, instead of trying to get free tech support by long-distance international e-messaging, you should try a mobile audio seller/installer near you in your own country. I'm sure a city like Cadiz or even Seville has a company or two that do such work and could help you.

  • David

    Posted on 7/15/2023

    Hello, I was looking for a configuration with 2 front component speakers (Alpine SPG-17 CS) + subwoofer (Alpine SBE 1244 BR) , all amplified by a 4-channel Crunch GPX 1000.4. The problem is, I dont actually know which materials I need, such as cables, wires, fuses...Also, I don't understand how are the front speakers connected to the amplifier and/or stereo and if the rear speakers would get disabled if left without changes. Thank you for your help.

    Connecting your car speakers to an amp: use your factory wiring (16)

    Connecting your car speakers to an amp: use your factory wiring (17)

    Buck Pomerantz from Crutchfield

    on 7/17/2023

    David, With questions like this, it's always better to have a conversation with a real live human. Give us a call and talk to one of our Advisors. We can help you choose the right gear and give you the right advice on how to install it.

  • Ryan from Urbandale

    Posted on 7/11/2023

    Curious, I have a 2019 RAM 1500 with the factory alpine system. I had an Alpine R2-A75M installed which is powering 2 S-Series subwoofers. I have gotten the itch and now am going to install all infinity reference in the car. REF-9632ix in rear doors, REF3022CFX in dash and still undecided what to put in the front doors and IF i replace the center channel and headliner speakers. With that, wondering if I need a new amp to power those? It is my understanding that the factory amp is roughly 500 watts, but unsure if the speakers will have sufficient RMS power based on that. If I do a new amp, assuming I can just jump power from a distribution center, but curious what parts I would need to avoid having to run new wire to each of the door and dash speakers, OR if running new speaker wire is advised in this set up?

    Connecting your car speakers to an amp: use your factory wiring (18)

    Connecting your car speakers to an amp: use your factory wiring (19)

    Buck Pomerantz from Crutchfield

    on 7/11/2023

    Ryan, Crutchfield's Research Team notes that replacing the factory low-impedance speakers with new 4-ohm speakers will result in reduced sound levels. The vehicle has a factory amplifier (of probably no more than about 10 watts RMS per channel) and will probably need a bypass or other kind of integration device and harness in order to add an aftermarket amp. Give us a call and talk to one of our Advisors. We can help you choose the right gear and give you the right advice on how to install it.

  • Anthony

    Posted on 7/8/2023

    If I have 4 speakers 2 in the front doors and 2 in the rear would it not be easier to just run speaker wire from the doors through the boot of the car back to amp? The same for the rear speakers which would be closer to the amp in the trunk? That sounds easier than running 8 leads from behind the receiver.

    Connecting your car speakers to an amp: use your factory wiring (20)

    Connecting your car speakers to an amp: use your factory wiring (21)

    Buck Pomerantz from Crutchfield

    on 7/10/2023

    Anthony, Some people think using the vehicle's factory speaker wiring and connecting the aftermarket system in one area behind the receiver is easier than running new speaker wires throughout the vehicle. But in your vehicle, it may be easier your way. It doesn't matter which way you do it, as long as the connections are correct and secure.

  • Claude

    Posted on 6/7/2023

    Great info from Crutchfield as always

  • Luis ponce from El sobrante

    Posted on 12/28/2022

    2019 Honda civic sedan what harness and adapters do I need to hook a amp and 8in.woofer

    Connecting your car speakers to an amp: use your factory wiring (22)

    Connecting your car speakers to an amp: use your factory wiring (23)

    Buck Pomerantz from Crutchfield

    on 12/28/2022

    Luis, As of right now, I don't see any T-harness adapters for Honda Civics. It looks like you'll have to hard-wire an LOC or an amplifier with high-level inputs into the Honda's system for your upgrade.

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