Connecting your car speakers to an amp
Tip: You can use your vehicle's factory wiring
Sending the audio signal from a receiver to 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.
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.
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.
Some products to help you do it
Our favorite option is the Crutchfield 9-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.
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?
Buck Pomerantz from Crutchfield
on 10/2/2023
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?
Buck Pomerantz from Crutchfield
on 9/29/2023
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
Buck Pomerantz from Crutchfield
on 9/29/2023
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.
Buck Pomerantz from Crutchfield
on 7/31/2023
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.
Buck Pomerantz from Crutchfield
on 7/17/2023
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?
Buck Pomerantz from Crutchfield
on 7/11/2023
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.
Buck Pomerantz from Crutchfield
on 7/10/2023
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
Buck Pomerantz from Crutchfield
on 12/28/2022
Jordan Ramirez from Parlier
Posted on 12/17/2022
How do I wire 4 front doors component speakers using the factory wiring to a 4 channel amp. I'm confused because I have seen a lot of people run separate speaker wires for mid and tweeter on each door but what do I have to do in order to power all 4 components with use the stock speaker harness wiring? I plan on leaving the rear speaker with stock power from the radio.