How To Hook Up A 4 Channel Amp To Front And Rear Speakers

Adding a 4 channel amp is a great idea. I’ve enjoyed powerful, crystal-clear sound in my vehicles for years using my own 4 channel amps.

But how do you hook them up?

In this guide I’ll show you how to hook up a 4 channel amp to front and rear speakers. After installing hundreds of amps in vehicles just like yours I’ll share with you the fundamental tips you need for great results.

And hey – don’t worry…in most cases you can do it yourself and get professional results on a budget!

Infographic – How to hook up a 4 channel amp (tips and general guide)

Hook up amp 4 channel amp front rear speakers infographic diagram

Basics first

If you’re reading this there’s a good chance you’re not familiar with installing an amp, connecting wiring, and other details related to hooking up a 4 channel amp in a vehicle.

Not everyone has installed car stereo equipment before so I’m going to be as thorough as possible and avoid making any assumptions about how much you know.

What is a 4 channel amp?

Holding Alpine MRV-F300 amp in my hand

Today’s 4 channel amps offer newer technology, better sound, and more compact size than in the old days. An excellent example is the Alpine MRV-F300 50W x 4 model. It uses Class D technology to run extremely cool and yet it’s small enough to fit under a car or truck seat. Very nice!

What a 4 channel car amplifier is may seem obvious at first but there’s a bit more to know Additionally, there are some interesting (and good) ways they differ from 2-channel amps.

In fact, there are actually a few benefits you’ll get using one 4 channel amp instead of 2 stereo ones to power your front and rear speakers.

A 4 channel amplifier is a stereo amplifier with 2 more channels built in to boost (amplify) weak input signals to a higher voltage signal. This drives speaker voice coils to move the speaker cone and produce sound.

4 channel amplifiers add more channels into a more compact and efficient design than separate amplifiers would have.

Additionally, they offer more flexibility, as most can be configured for “bridged” operation which can give more power when you don’t need all 4 channels.

What is “bridging” an amp?

Bridged mode capability is a special design feature in which a “push-pull” set up is created: one channel (normally used for the left speaker) produces a signal that’s the opposite of the second channel (normally used for the right speaker).

This causes the speaker to receive a voltage audio waveform that is the difference between the two channels – resulting in more available power to speakers.

Essentially, bridged mode is a flexible way to get more power if you’re not driving 4 speakers. It means 2 channels are sharing the workload of one speaker between them and therefore and drive it with more power.

2 channel vs 4 channel amp diagram

2 channel vs 4 channel amp diagram

A 4 channel car amp is basically an expanded version of a 2-channel amp. However, because they’re built together and not 2 separate 2-channel amps, they’re more compact. This saves installation space and makes it easier too. Additionally, most can be bridged to use 2 channels (or 3, depending on your needs) so you’re not restricted to using them with only 4 speakers.

The benefits of using an amp to drive speakers

Whether you have a factory stereo or a great aftermarket (non-factory) one, adding an amplifier is one of the best decisions you can make.

In-dash stereos are very limited in how much power they can produce. They can’t drive speakers with the same clarity and low distortion as a good amplifier can.

The maximum volume you’ll be able to get from your speakers will be pretty low, too.

There’s simply no way around it – most in-dash stereos are limited to about 15W-18W RMS of power for each speaker channel. That’s because they’re running directly from the +12V supply. Amplifiers are unique in that they take the +12V electrical supply and boost it to a higher voltage.

When a signal is boosted and sent out to your car’s speakers the voltage is much higher and the speaker can receive much more power.

That’s why tiny amplifiers are rarely worth bothering with – if there’s no special power supply inside, it’s simply not capable of producing much power.

Getting great sound

Powering speakers from an amp makes a big difference, and I’ve enjoyed excellent sound for years this way.

When an amplifier drives your vehicle’s speakers it’s often not even pushed to its limits. The sound produced at the speaker has lower distortion, doesn’t “bottom out” when heavy bass is played, and you can get a lot more volume, too!

Additionally, using an amplifier with built-in high-pass crossovers means you can block out lower-end bass that causes your speakers to distort and attempt to play music tones they’re not suited for.

The result is cleaner sound, less distortion, and great volume – you can crank your music even higher!

Just imagine driving down the road with the windows open and finally being able to blast the music you love. I’m confident you’ll love it as much as I do.

Things to know before you start

Clip art image of a face thinking - Things to know content image

It only takes a few minutes to make a list of the parts, wire, tools, and other bits and pieces you’ll need. Planning ahead can mean the difference between getting your system going without major problems or having a frustrating time – or complete failure! I always get organized and get my items together before I start a job.

Planning ahead is very important. You don’t want to run out of wire or discover you don’t have the rights parts, for example. That will mean you can’t finish your project.

It’s even worse when you have to drive around town searching for items or you’re not able to do anything after the stores close. Believe me, I’ve been there, and it’s terrible!

Notes about wire, tools, and a few other things

When it comes to installations, always plan to have more, rather than not enough, wire. This goes for speaker wire as well as RCA cables.

The amplifier kits I recommend have the right length for your amp installation, but speaker wire & RCA cables are another matter in this case.

What length and size speaker wire do I need?

wire of 16 ga speaker wire

There’s no need to spend an excessive amount of money on speaker wire. 18 gauge is enough for many installations, but 16 gauge is a great choice too if the price is right. A great example is this AmazonBasics 100 foot roll. I recommend a 100 foot roll for many installations with a 4 channel amp (see why below).

Here’s an estimate of the worst-case scenario for the length of speaker wire required. I’ll use the example of installing an amp using speaker-level inputs, with the following typical installation:

  • Amp is located in the trunk
  • Speaker level signal connections near the radio (center console)

Let’s use roughly a 15′ length of distance from the radio to the amp. That’s a good estimate in my experience.

So we have:

  • Wire from the radio to amp (signal wire): 4 channels x 15′ = 60 feet
  • Wire from the amp to speaker wiring near radio: 4 channels x 15′ = 60 feet

Total estimated wire required: 120 feet.

That means you need 2 100 ft rolls of wire. Or at the least, 1 100 ft roll and 1 50 ft roll. If you’re planning to use a line-level adapter, expect to pick up a 100′ roll.

If your installation is using RCA jacks, expect a 100 ft roll also (4 channels x 15′ length estimate for the speaker wire from the amp).

What about RCA cables?

KNU Conceptz KCA-K4 4 gauge amp wiring kit RCA cables imageIf you’re installing a 4 channel amplifier and using RCA cable connections, you’ll need to buy a 2nd pair along with your amp wiring kit, as most only include a 2-channel cable.

For most installations, I recommend 18′ length cables. That’s usually long enough for most vehicles and you should usually have enough length to hide the cables inside the interior and under the rear seat, etc.

There’s no reason to spend an excessive amount of money. Just pick up some good quality, well-made cables. Even a pair like these value-priced ones will be fine in most cases.

Tools you’ll need.

Image showing example crimp tool and crimp connectorsCrimp tools are great for installing your amp and speaker wiring with professional results. If you’re doing your own installation, you can get by with an inexpensive tool like this Pros'Kit crimp tool. Crimp connectors are sold separately in many automotive parts stores or general stores and are very affordable.

I recommend a few tools. If you shop carefully, you can avoid getting ripped off on tool prices. When connecting speaker wiring to factory wiring, it’s easier to use crimp connectors than solder.

Never simply twist the wire together and wrap it in electrical tape. Always use a reliable connection.

During warm weather, electrical tape adhesive can fail and the tape can come off of the wire. This exposes it to possible short circuits and potential damage to your radio or amp.

If you have access to a cordless drill, that’s fantastic! They’re great for drilling holes in the vehicle’s metal for mounting your amplifier or connecting the ground wire to bare metal.

I also recommend the following:

  • Wire cutters (some crimp tools have this built-in)
  • Roll of quality electrical tape
  • Wire ties (“zip ties”), 6″ length, bag of 100
  • A digital test meter for voltage measurement

Etekcity MSR-R500 digital test meter example

A test meter is often incredibly helpful when installing an amplifier. However, you don’t need to spend much money! A basic but good budget model like this one at Amazon will work great.

I recommend getting an affordable but good digital test meter to find a switched +12V wire for getting a remote-on signal to the amp.

They’re also extremely helpful when troubleshooting power problems when something isn’t working.

Get your installation shopping list together

Image of a paper checklist being prepared with a marker

Here’s a general but pretty accurate list of what you’ll need for connecting a 4 channel amp to front and rear speakers.

Installation types 1 or 2: Factory radio or no RCA connections

  1. 4 channel amplifier with speaker level inputs or amp and line-level adapter
  2. 120 feet or more speaker wire, 18 gauge or larger
  3. Amp wiring kit
  4. Crimp tool and butt (wire crimp) connectors (25 or more at least)
  5. Cutting pliers
  6. Electrical tape
  7. Wire ties, 6″, bag of 100
  8. Test meter

Installation type 3: RCA connections

  1. 4 channel amplifier with speaker level inputs or amp and line-level adapter
  2. 100 feet roll speaker wire, 18 gauge or larger
  3. Amp wiring kit
  4. Additional RCA cables, 18′ minimum
  5. Crimp tool and butt (wire crimp) connectors (25 or more at least)
  6. Cutting pliers
  7. Electrical tape
  8. Wire ties, 6″, bag of 100
  9. Test meter

Be sure to plan well and estimate the amount of speaker wire you’ll need. For the amp installation itself, I strongly recommend using a pre-made amp wiring kit like you’ll find here in my amp kit buyer’s guide.

You’ll also need to get a 2nd pair of RCA cables. I recommend 18 ft length or more. Don’t spend too much money, but do get decent quality ones.

How to get a signal to your amp

Example of the rear of a car stereo installation closeup

Image of an aftermarket (non-factory) stereo showing the RCA jacks and speaker output wiring. Either one can be used for getting a signal to an amp, but RCA jacks offer a better option. They’re normally lower distortion and allow using plug-in RCA cables. If those aren’t available, either an amp with speaker-level inputs or a line level (speaker level) adapter can be used.

In order to install a 4 channel amp and drive all 4 speakers, in many cases, the biggest obstacle is getting a signal to the amp. Once that’s done, the rest is usually a standard amp installation.

There are 3 basic ways to get a signal to your 4 channel amplifier:

  1. Connect speaker outputs to your amp’s speaker level inputs
  2. Connect a line-level adapter to the radio then use RCA cables to the amp
  3. Connect your radio to the amp using RCA cables directly
NOTE: I won’t be covering factory sound systems that are “premium” and have a factory amplifier. Those such as Bose, JBL, and Mark Levinson, often found in luxury vehicles or special-edition models, are much more complex and harder to deal with.

In that case, my advice is to speak with a good installation shop first and do your research.

If you feel that factory amplified systems should be here as well, send me a message or comment and let me know

In a few cases, adapters are available to connect an amp to a factory amplified system’s audio wiring, but it’s often difficult or there are obstacles you won’t find until you get started.

One of the reasons why is that factory amplified systems often have non-standard wiring connections for the audio path and are prone to bad noise problems if you connect an amplifier without the proper adapter or wiring.

Which type of connection do I need?

If you have a radio with RCA jacks, skip on down to the next section.

However, if you have a stereo with no RCA jacks (which is always the case for factory-installed stereos) you’ll have to buy one of the following:

  • A “line level” converter
  • An amplifier with speaker-level (“high level”) inputs

1. Line level converters

PAC LP7-4 4 channel line level converter

Line-level converters like this PAC LP7-4 4-channel model are designed to take speaker-outputs from a stereo with no RCA jacks and adapt them to RCA jacks. Using this, you can run RCA cables to your amplifier.

Line level converters are designed to allow connecting to an amplifier’s RCA inputs by converting speaker outputs from a stereo to a low-level signal an amp can use.

It’s very important to buy a quality, well-designed line-level adapter to avoid noise, poor sound quality, and other problems. Don’t get the cheapest – instead, get a name brand model you can rely on (like the one above).

2. Speaker level inputs

Car amplifier speaker level input example
Amplifiers with high-level (speaker-level) inputs like this one allow connecting to speaker wiring for a signal source. This avoids having to buy a separate adapter.

Speaker level inputs are common on many 4 channel amplifiers. These amps contain electronics that scale down speaker wiring signals to a lower signal safe for the amplifier’s input circuitry.

They’re simple to connect: normally it’s just a matter of connecting both positive (+) and negative (-) wiring for each speaker channel on a small wiring harness included. This then plugs into the speaker level input connector.

4 channel amp speaker level harness example

A typical speaker-level input harness for a 4 channel amp. The wires are color-coded to make installation easier. White = left front, gray = right front, green = left rear, and purple = right rear.

While it can save money (you won’t need a line-level adapter in this case) I often recommend that people consider buying a line-level converter anyway.

This allows an easier upgrade for your stereo later, which is very common for people to do. Using the line-level converter now will allow you to run RCA cables to your 4 channel amp to be used later if you buy a better stereo (which will include RCA jacks, almost always).

3. RCA jack (line-level) connections

RCA jacks offer a clean, lower-noise connection than speaker-level adapters do, but honestly, it’s not noticeable to the average person. RCA cables (line-level connections) are the preferred way to connect a signal to your amp if you have that option.

RCA jacks on the rear of a Pioneer head unit. This is the ideal way to connect your amplifier’s signal inputs, if available. For a 4 channel amplifier, you’ll need 2 stereo RCA cables to do so. White represents the left channel white red represents the right. These are standard colors for audio outputs for both car and home stereo.

If your stereo has RCA jacks, then congratulations. Things just got a bit easier – and potentially better sounding, too!

You’ll need 2 stereo RCA male-to-male cables (4 audio channels total) to run from the radio to your 4 channel amp. That’s 4 signal channels: left & right front and left & right rear.

4 channel amp signal connection diagram

Here’s a helpful diagram showing the most common connections you’ll need to make one of the 3 most common cases I mentioned earlier:

  1. Connecting to your amp’s speaker level inputs
  2. Using a line-level converter
  3. Connecting your amp to the radio’s RCA jacks

4 channel amp signal connection diagram
You can also click here to view the .pdf document for print or download.

Connecting and running signal wiring

Speaker-level connections

As mentioned above and as shown in the diagrams, if you’re using speaker-level outputs to get a signal from the radio, you’ll need to connect wire. Ideally, you’ll do so near close to the radio, then run the wire together as a bundle.

You can bundle speaker wire together with wire ties to keep it neat and make the installation easier.

Estimate the length of speaker wire you need to reach the amp (or line level converter) for each audio channel. To do so, run a length of wire from the radio to where the amp will be installed, then allow a little extra and enough length to run around curves and interior parts.

Cut 7 more lengths of wire, for a total of 8:

  • 4 channels (4 pairs of wire) going to the amp’s speaker level inputs
  • 4 channels from the amp to the radio’s factory speaker wiring

Image of car stereo wires crimped

I recommend connecting to speaker-level outputs using crimp connectors and a crimp tool for a reliable, solid connection. Blue connectors are normally the right size for 18-16 gauge wire.

Factory stereo color codes

If you have a factory stereo, you’ll need to find the wiring colors for the speaker wiring.

A great resource for that is, where you’ll find wiring diagrams for your vehicle and color codes listed.

Making connections

Image of factory stereo wiring harness

After removing the radio you’ll find connectors like this for the factory stereo wiring harness. You’ll need to separate the speaker wires, cut them, and attach wiring to run to the amp.

Remove the radio and disconnect the factory wiring plugs or aftermarket radio’s wiring harness.

Cut the speaker wires, leaving enough length to move the wire and to have enough length to connect to the wire freely.

Strip a small part on both the stereo’s speaker wire and your amp speaker wiring. If using a line-level adapter, connect to the stereo’s speaker output side. Then connect the 4 pairs of wire to the speaker wiring in the harness.

Insert the stripped wire (about 1/4″ of bare wire) into the connectors and crimp them carefully using a crimp tool if you have one. Alternately, you can twist together wire, solder it, and carefully wrap it with electrical tape or use heat shrink tubing for insulation.

If using speaker level inputs on your amp, also connect 4 pairs of wire to the output of the stereo.

Wire bundle with zip ties example

To make a neater, more professional installation, bundle the speaker wiring similar to this using wire (“zip”) ties. I recommend using 6″ ties which often are sold in packs of 100.

Once all wiring is connected, bundle it up using wire ties or, optionally, a little bit of electrical tape wrapped around. In both cases spacing out wire ties or tape about every 1″ or 1.5″ along the length of the wire works well.

Connecting RCA cables

Example of connecting RCA cables to rear of a car stereo

Connecting RCA cables to an aftermarket (non-original) stereo for running to an amplifier.

If you’re using a line-level converter or have a stereo with RCA jacks, connect all 4 cables plugs to the front and rear outputs.

RCA cables are sometimes marked with left and right symbols (“L” and “R”). In some cases, white, clear, or some lighter color can be used to represent the left channel.

Connect the cables consistently so you’ll be able to recognize which one is which. If the front and rear RCA cables are the same, you might want to mark front and rear using some masking tape and a marker or pen.

Connect the remote-on amp wire

Don’t forget the remote wire! Amp wiring kits include a small wire that’s used to connect the amp so that it switches on and off with the accessory position of the ignition switch.

Locate a +12V wire that has power when the ignition is switched to “ACC” or similar but turns off with the key. You may also have good luck finding an existing wire color from vehicle wiring diagrams I mentioned earlier or from a Google search.

I recommend checking the wiring even if you have already located it online, just to be sure.

Before re-installing the radio connect this wire and run it alongside the speaker wiring.

How to connect a 2 ch. car stereo to a 4 channel amp

Diagram showing a 2 channel car stereo connected to a 4 channel amp

You can connect a head unit car stereo with only 2 channels (left and right) to a 4 channel amp easily. Ordinarily, all you need is 2 RCA Y adapter cables. The head unit’s left channel RCA jack should be connected to the left front and left rear amp inputs. Likewise for the right channel. If using speaker level inputs on the amp, use the connections shown above. NOTE: Use only ONE of the two connections above! Never connect both types at the same time! Speaker-level outputs will damage RCA connections.

If your head unit (car stereo) only has 2 RCA jacks or two pairs of speaker outputs, that’s not a problem.

As shown in the above diagram, you can connect 2 channels to a 4 channel amp using either the speaker level inputs wired in parallel or by using simple RCA adapter cables.

RCA y adapter cable image

All you need is a decent pair (a total of 2) female to male RCA “Y” adapters like these low-cost ones from Amazon.

The sound quality will be exactly the same. Today’s amps are designed in such a way that there’s no harm in using a Y adapter to connect the amp. The amplifier will receive exactly the same signal, with the same quality, in the front channels as well as the rear.

The only drawback is there won’t be a front to rear fader control like with head units with 4 channels of outputs.

After connecting the stereo to the amp, you’ll need to adjust the rear gain to set the volume level for the rear speakers as needed for the proper volume depending on the stereo’s signal strength.

Installing the amp

Product image of Belva BAK82 amp wiring kitAn amp wiring kit like this one will make installing your 4 channel amp much easier. A good-quality one like this Belva 8-gauge complete kit includes not just wiring but much more. You’ll also need to pick up a 2nd pair of RCA cables (if using them) and enough speaker wire.

Your amplifier needs a good solid metal connection to ground and you’ll need to run the positive battery wire to the engine compartment. Your amp wiring kit will also include a fuse holder that should be installed near the battery as well (most kits include instructions, by the way).

You’ll also need to connect the amp’s speaker outputs to the wire you ran from the radio.

As it also applies to 4 channels amps, for the amplifier installation you can follow my guides here:

Here’s a basic diagram as well to help:

How to install a 4 channel amp diagram

Setting up your amp

Alpine MRV-F300 4 channel amp end viewOnce installed, you should set up your amp’s gain levels and crossovers for the best sound. In this image, you can see the adjustable crossovers for both front and rear channels. Turn on the high-pass crossovers and adjust to a setting close to 50-60Hz, to allow good bass for music but block low-end bass that distorts.

Once installed, you’ll need to set up your amp’s gain levels and crossovers, if available. Most sold today have that. (See my recommendations at the end for some great models)

Gain control is the amount of signal amplification the amplifier performs. Ideally, with a good input signal, it can be kept low to reduce any hiss or noise that can appear when it’s turned up high.

Here’s a great rule of thumb for how to adjust the gain for this type of system:

  1. Turn down gain controls on the amp
  2. Turn the stereo’s volume to 2/3 of maximum
  3. Slowly raise the gain controls until the volume is enough

When finished you should have enough volume available from the stereo but noise should be minimal. You’ll still need to tweak it a bit if the volume is too high or too low.

Setting the crossover

As I mentioned at the beginning of this guide, using high-pass crossovers will allow more volume with less distortion and will help protect the speakers from heavy bass.

For both front and rear channels turn on the high-pass feature and, if an adjustable dial is available, set it near 50 to 60Hz. Some models don’t offer an adjustable frequency for the cutoff but are likely preset to a good level.

Test and tweak

Once installed, test and tweak your amplifier as needed. A great way to mount your 4 channel amp is by using a board mounted to the car, covered with speaker box carpet or other material.

Play some music you’re very familiar with and adjust things like bass, treble, and the fader as needed. Using music you’re very familiar with (of high quality) means you’ll be able to notice any problems with the sound fairly easily.

If you don’t already have one, you might consider later upgrading to a head unit with built-in equalizer (EQ) functions to help tailor the sound.

Summary and recommended products

Hopefully you’ve found this post useful. Hooking up a 4 channel amp to your front and rear speakers takes some work and time, but it’s a great way to get sound you’ll love.

Considering buying an amplifier? You can find some great 4 channel amps (including the Alpine MRV-F300 pictured here) in my 4 channel amp buyer’s guide.

You’ll also need a good amp wiring kit – I’ve got a good amp kit buyer’s guide here.

If you find anything missing or have suggestions, just leave a comment below or send me a message!

Your comments are welcome!

  1. Thanks for your great write up. I only have 1 pair of rca outputs on my HU. Can I just use 2 pairs of y splitters to send the RCA signal to 4 channels or will I lose some quality?

    • Hi there, Taylor! I appreciate your comment and the question, too. It’s a good question!

      Yes, you can use 2 Y RCA cable adapters to send 2 RCA outputs from the head unit to 4 inputs on an amp. The amp is designed in a way that it won’t matter, and it won’t hurt anything.

      The signal quality should be basically exactly the same (unchanged) for all 4 inputs to the amp.

      You’ll just need to use the gain on channels 3 & 4 to set it like a fader when getting it set up. I would set the front pair first correctly and then worry about setting the rear channel levels.


    • WOW! The best info I have found! And I have been looking for a while. Many thanks! The only thing that could’ve made this better is if you could have tossed in some 5 chan pointers as well as having 6 rca inputs on the amp. I’m stuck but at least not as in the dark.

    • WOW! The best info I have found! And I have been looking for a while. Many thanks! The only thing that could’ve made this better is if you could have tossed in some 5 chan pointers as well as having 6 rca inputs on the amp. I’m stuck but at least not as in the dark.
      Marty, can you please, please maybe edit and talk about 5 channel amps? I’m getting sound that’s either L and should be R or Rear when it’s marked front… Bizarro world, man!

      • Hi Serge & thanks. Well in this case I was focusing on 4 channel amps as per the topic. I’d need a bit more info regarding your particular system.

        If you’d like to message me directly (see my Contact page) you can reach me there. Also, be sure your 5 ch. amp’s 2/4/5 input switch is set to 4 or 5 if you’re wanting separate front/rear fader inputs.

        Thanks. :)

      • Hi Marty im hooking up a 4 channel amp to my HU will I still be able to use the balance/fade and eq options from my HU? Thank you so much in advance. Your diagrams have helped me tremendously. I spent hours researching and thank god i came across your site.

    • Marty,
      Im new to this so forgive my ignorance, please.
      I have a Sony head unit with 2 rca plugs at rear. 4 6x9s and a 1500 watt 4 channel amp.
      I have speaker wire ran from the amp to all 4 speakers. The blue remote wire is connected from radio to amp everything is grounded good and I have power to radio and amp with the fuse holder. The amp is a blaupunkt 1404 and the rca plug labels are a little confusing. Should I be plugged into output or input on the amp end? Ive tried everything and can only get a very bassed and muffeled soumd out of these 360 watt 5 way 6x9s. I know they should be cranking. Ive tried adjusting the gains and switches. Please help

      • Hi Jerry. The head unit’s RCA outputs should be connected to the RCA input jacks on the amp. The outputs let you connect the RCAs to another amp if you like.

        If you’ve got the amp’s crossovers set to full or high-pass (“HPF”), and you’re still not getting sound as you should, my next thought is to be 100% sure you’ve got a good ground and power. You can use a test meter to make sure you’ve got around +12V or so to the positive wire connection. Similar for the remote wire.

        Then make the ground wire goes to a good bare metal connection attached to the vehicle body. Also be sure the Sony RCA outputs are not set to subwoofer mode if it has that option (some models can be switched between full-range or subwoofer outputs).

        If those check out, I would temporarily test the amp outside of the vehicle to make sure it’s ok. You can do this by using some small wire to hook it up to the battery or a +12V supply with a few amps of power. For the signal you can use your phone and a 3.5mm to RCA adapter to connect directly to the amp and play music.

        But I would be 100% sure the amp installation is right, as that’s most likely the problem.

    • I’m installing 4 channel amp with rca for signal. I wired it exactly like system 3 diagram. Getting nothing. I already had a sub hooked up with a line level adapter..sounded nice but I wanted more from my door speakers. Could my sub be affecting my 4 channel amp because of the line level adapter I used to hook it up. So far your diagrams have helped out tremendously but I’m stumped at this point

      • Hello, Louis. Ordinarily the subwoofer amp/etc shouldn’t be able to affect the 4 channel amp. Assuming everything is installed correctly and there’s no factory amplifier to bypass, there shouldn’t be any issues.

        So that leaves me with a few questions:
        – Have you verified that the 4 channel amp is installed & working as expected? You can you temporarily hook up a test speaker to one of the channels to make sure you’ve got sound
        – You mentioned that you’ve already got a line level adapter, so how are you connecting the signal for the 4 channel amp?

        Usually it comes down to one of the basic things. If you’re powering factory speakers like as shown in the diagram, you can use a 9V battery across the factory speaker wiring in the dash to make sure they’re working (and they don’t have a factory amp in between). I’m not sure what vehicle you have so that’s something to bear in mind.

        Mainly though I would start with the amp & makes sure you’ve (1) got a good signal input to it and (2) the amp is powered up right & producing sound for sure.

        I hope this helps!

        • Thank you very much I’ll give it a try and test the app again but I do have a line level run in the sub and I was going to use the line level to run to Fortuna Lawsona it’s for an F1 50

  2. So going off what you’re saying it seems like you run your speaker wire out put from amp back to behind stereo and then connect the to the wire harness which then is using the stock factory speaker wire to feed the speakers in doors. Do you find any difference in avoiding the factory speaker wires to speakers? Meaning run new speaker wire from amp directly to each speaker. I was going to run with 16g this way, directly from amp to each speaker. If I do it your way and run from amp to behind head unit and use the factory wire from behind head unit to speakers will I lose any sound quality or power?

    I’m not sure what size the factory speaker wire is running throughout the vehicle.

    Installing in a 2001 Ford ranger XLT extended cab

    Here’s my product information-
    -I’m using two sets of RCA
    – 4 guage power supply
    -Jbl GX862 speakers
    -Jbl GX-a604 amp
    -Pioneer DEH-6000BT head unit

    • Hello, Chris! Thanks for visiting the site & for the comment.

      Usually factory speaker wiring is around 18-20 gauge or so, which is fine for this kind of system. Yep, you can just run the speaker wire from the amp to the factory wiring. Ideally you can use a harness adapter to avoid having to cut the factory wiring.

      In this case you won’t lose any sound quality or power. It’s when you get to much higher power ranges that it makes a difference.

      That looks like some nice items you’ve picked up so I’m sure you’ll enjoy them. One comment I do have is that the 4 gauge power supply is larger than you need for that amp. If it’s not already installed and you haven’t run the wire yet, I’d use 8 gauge.

      That’s a bit easier to deal with especially when going through the firewall. Also, 4 ga. wire may not fit well on the power terminals on that amp.

      I hope this helps!


    • Recently installed a pioneer avh 211ex as well as all new speakers to a 4 channel amp wired with rca cables. We’ve tried everything and can’t get any sound to the speakers anything we’re missing? If you need more info let me know. All help is appreciated.

      • Hi Miller. As some details are missing, I’m assuming you’re trying to set up a system like the following:

        AVH 211EX -> [RCA cables] -> Amp -> speakers (directly wired). If that’s not the case please let me know.

        I would verify the amp is working ok by using a test speaker wired to it directly and also connect your phone or other audio source directly with a headphone to RCA cable adapter. That way you can be 100% the amplifier is fine.

        If that works, then connect the AVH211EX to another amp or home stereo (outside the vehicle) to verify the RCA signals are working. They should be, as that’s not a problem I’ve seen much.

        Also, be sure to make sure that audio outputs aren’t disabled in the menu settings. Check your manual. Some head units offer the option to turn off the speaker outputs or RCA outputs.

        Are you using the speaker outputs?

        What we would normally do in a case like this is do a “bench test”: Remove the stereo and amp and test each one separately with a separate ratio or speaker we know for sure works to see which one isn’t working as expected.

        Without more details those are my best suggestions.

        Good luck!


  3. Great info!
    I have a mrv-v500 5 channel amp hooked up and 2 subs. I’m using a jl fix 86 processor because I did not want to change my head unit so I kept it factory. If I want to change my head unit, using the rca out puts from head unit to amp is my best choose right? Also I’m guessing I would have to remove the processor since it would be a aftermarket head unit.

    • Hello, Julio! Glad to hear from you. I’m glad you like the content.

      Yes, if you change the head unit, using the RCA connections would deliver the best sound. However, the good news is that you won’t need to get rid of the FiX-86. It will accept a wide range of input levels and should work with RCA (line-level) inputs.

      However, you’ll need to use some RCA to bare wire adapters or cut cables to connect it, according to what I saw in the owner’s manual. There should be some items you can find that will do the trick.

      If you can’t find any let me know and I’ll look one up for you.

    • Hello!

      I am writing from Colombia.

      Thank you so much for this incredibly clear information it has been very useful!

      My car is a Toyota Prado land cruiser 90series. I bought a pioneer AVH-205BT headunit and 2 pairs of 165 vrs focal
      Components. The components are connected to the factory wires. Thanks to your article I understood how I could use de RCA audio with an amp to improve my audio quality, but I found out I have 2 subwoofer output in the head unit LSW RSW. All the guides I have seen speak about a single subwoofer, but don’t explain how to used this outputs.

      My questions are:

      1. ¿How do this subwoofer outputs work? In the case scenario that I just a 5 channel amp how am I supposed to connect the single subwoofer speaker to the amp out, and also how do I connect the amp input since there are two subwoofer output from the headunit?

      2. ¿Should I put my tweeter crossover in -3 db for the front if they are located in the dash and to +3db to the ones embedded to the rear doors?

      3. ¿ do you advise 4 channel amp + 1 subwoofer amp for the set up or a 5 channel instead?

      4. ¿How much power I need in my amos for the components to sound correctly ?

      5. ¿How big and powerful I need my subwoofer to be?

      Thank you so much for your help!

      • Hola, Andres! My apology, for some reason I did not see notice of your comment before.

        Thanks for your time here (gracias para tu tiempo aqui!)

        1. Generally, the subwoofers RCA outputs are MONO outputs, but not always. How you connect it to the 5 channel amp depends on the model & design of the amp. But generally you can just connect both of the head unit subwoofer RCAs to the amp’s subwoofer inputs.

        5 channel amplifiers have a mono bass channel it will produce a mono signal output. You will connect one or more subwoofers according to the owner’s manual and it should be fine.

        2. Yes, you probably should use -3dB, but really it’s best to try it and see. Most likely yes, it will be slightly better with +3dB for the rear doors since the highs are facing away from you and you lose sound on them.

        3. This is a “it depends” situation. For some people a 5 channel amp is plenty, especially the new models like Pioneer GM series with so much power. If a 5 channel amp has enough power per channel + the subwoofer channel, I would say yes.

        However, for people who need more power in the main channels and/or subwoofer output, 2 amps may be better. However, a 5 channel amp saves spaces and makes installing easier to. It depends on what your needs are.

        4. I recommend 50W RMS per channel at least for regular component or coaxial speakers

        5. ~150W RMS subwoofer power at least for decent bass sound, but 200-250W RMS or higher is much better. I would always use a 10″ or larger. I wouldn’t recommend 8″. (When picking a subwoofer or pair of subs, the larger the size the better in general since larger cones = moving more air for more bass).

        Thanks for stopping by!

    • Sorry one more question. On the back of my HU it has two blue inputs that say sub 1 and sub 2 does that mean i can hook a two 2 channel amp to those for an sub?

      • Good morning, Nicole! I’m glad you found my diagrams helpful. I work very hard on them and I try my best to make them easy to understand and useful.

        That’s odd that your head unit has blue inputs, as RCA jacks are (nearly always) white (left channel) and red (right channel). Without the brand and model number it’s a bit harder for me to say.

        If your head unit has front AND rear outputs yes you can use a front/rear fader control when using a 4 channel amp. If a head unit only had a single pair of RCA outputs (usually rear and/or subwoofer output) then you can’t. In that case you could use speaker level inputs on an amp or a 4 channel line level converter to connect both front and rear channels to provide a fader.

        I hope this helps! Thanks.

  4. Hi, i have pair of focal 165 vrs (60rms) running through hertz he-4 (75watts rms x 4 at 4 ohm) and the speakers sounds bad no bass. I have connected them on channel A and have sub on channel b bridged. Any idea why they dont sound good. What possible i have done wrong ? Btw i run 16g wire from amp to front hu wiring harness then using factory wiring. (Audi a3 8p). Thanks!

    • Hi Pawel. You don’t mention what stereo you’re using and a few other details like that, so I’ll answer the best I can based on what you wrote.

      1. Are you using the high-pass crossover function on the front speakers? If so, switch it off and see the result.

      2. How did the factory speakers sound? Was there good bass for those? If yes, that leads me to believe it’s either installation related or the speakers won’t perform well in the doors as they are now.

      3. You need to be 100% sure that there’s nothing in the factory speaker wiring that could be causing an issue. To verify this, temporarily use some speaker wire to bypass the factory wiring you’re currently using. If that changes the sound, there’s likely some type of crossover component in the factory system causing the problem.

      Unfortunately, not all speakers will sound good in all car doors. If there’s not a decent enclosure (if there are bad air leaks, etc) poor bass happens. In that case it’s installation-related and you’ll need to try to seal off the doors where the speakers are installed.

      Don’t worry about the speaker wiring size – that’s not going to cause poor bass response.

      Hopefully this helps. :)

  5. Nice site – I’ve got a related but slightly different question that you may be able to address. I have a 4 channel amp (JBL GX-A604 435W) that I haven’t connected yet, a total of four JBL Stadium GTO 620 speakers in the doors, and a pair of JBL Stadium GTO 750T tweeters in the dash, for a total of six speakers. I’m currently using the factory wiring with an aftermarket head unit and everything sounds OK.

    This is a temporary situation – I bought the amp with the intention of running new speaker wire and RCA cables for signal and connecting all the speakers. Easy enough, right? I had planned on just hooking up the two front door speakers to the tweeters in parallel (two channels) and then hooking up the rear door speakers to the other two channels.

    The problem is that all six speakers are 2ohm, and while the amp is also 2ohm, it’s my understanding that connecting in parallel would drop that down to a total of 1 ohm, or wiring in series (which is a bit more complicated in tight spaces) would increase it to 4ohm and may reduce sound. Am I overthinking this or is this a problem?

    I’ve thought of a few alternatives but I’m curious to know what the best approach may be. One idea I had was to just leave the dash tweeters on the factory wiring and let them get a signal / power that way, while using the RCA output to the amp to drive the four door speakers on each of the four signals. Not sure if that would even work, or if it would introduce problems with delay or something else. What’s the best approach to get the most sound out of the 6 speakers? Thanks!

    • Hi MJ and thanks for dropping by! I took a look at your speakers & etc. (thanks for providing enough detail, it makes a huge difference!)

      So there’s not a “perfect” way to approach this, but I can think of 2 solutions at this moment. As you might expect, both have pros and cons. And to answer your question, yes using speakers in parallel does drop the total speaker load the amp will see. It will be 2 ohms/2 in this case, or about 1 ohm, which is too low for an amp.

      Here are 2 ideas:

      1. You can use both the tweeters and the GTO 620 speakers on the front channels by adding inline (series) power resistors, 1 per speaker. By doing so you’ll be able to raise each speaker’s total impedance load (resistance) to 4 ohms. Therefore if we do this for both the tweeter and GTO620 speaker on each channel, when wired in parallel the amp will get a safe 2 ohms load.

      You can see an example of the wiring set up in section #3 in my wiring diagram here: Wiring diagram for adding inline resistors for adding more speakers safely.

      In this case you’ll 1.5 ohm resistors with a 35W (or higher) rating. You’ll need 4 total. The trade off here is that while it lets you use 4 speakers on the front 2 amp channels, the resistors will consume a good portion of the available power. So it’s wasting power, basically.

      2. (Ideal solution) You could get a 2nd amplifier just for the additional 2 GTO 620 speakers. There are many good budget 2 channel amps that would be great for this. While it’s not always fun wiring a 2nd amp, you’ll get more control over the gain/volume for the tweeters and front speakers by using the JBL just for them, then use the 2nd small amp for the rear speakers.

      Note: While you can use the tweeters directly from the head unit, the power output & volume after a certain point won’t match that of the amp. Head units are very limited in power they can provide (15-18W usually). There won’t be an issue with delay, though.

      You could use a very compact class D 2 or 4-channel amp for the rear speakers for example. If it were me, for the best sound quality and ability to adjust the sound I’d go with option #2.

      My advice would be if you’re strongly considering using the tweeters with the factory wiring, try that temporarily to see what you think.

      Then go with one of the other 2 options if that doesn’t make you happy. Personally I would use #2 from the get-go as it’s a sure thing.

      I hope this helps! :)

      • Thanks, big help! If you can drop a few links for compact amps that would pair well I’d be happy to click through.

        That sounds reasonable if I can fit everything – I’ve got a compact sub under the passenger seat so I’m trying to fit anything under the driver’s, space is limited.

        I’m assuming I’d need to re-run something like a 0/1 power cable from the battery to the block and split it out via distribution block to three 8 gauge power cables for the existing amps, and then find a single ground point to tie in all three… And the grounding is another question. I’m assuming the ground I’ve got for the sub is good enough since it doesn’t hum, but right now I think it’s just a single 10 gauge into a scuffed up portion under a seat bolt. Think I’d need to use a distribution block for the grounds too, or can stuff like this be grounded individually in a car without too much worry for ground loop noise?

        Again, very happy to take any links if you have recommendations. I’m thinking I’ll end up having to pull out both front seats this time after all.

        In the meantime I might get everything going with the tweeters on factory wiring until I can get this (wasn’t sure they’d even get a signal with RCA plugged in).

        Also, I found that with my car (Impreza) I can run cables through the rubber door boots without disconnecting anything but trim, by using a heavy duty 3 foot long zip tie with the tip bent up slightly like a ski and the other end snipped off, and a little windex for lube. MUCH faster technique than most guides I’ve read.


        • Hi MJ. Sorry for the delay as I was having Wi-Fi problems last night. There’s a lot to cover here so I’ll try to keep it organized.

          1. Here are 2 very good amps that are both good values and compact:

          Alpine MRV-F300 4 channel amp (bridgeable). It’s fairly compact, and sounds very good. It’s also just a good value.
          Alpine KTP-455U micro amp 4 ch./bridgeable. This is a super-compact amp (a tiny 7-7/8″W x 1-1/2″H x 2-9/16″D) and can fit in a LOT of small spaces. It’s 45W x 4 or 90W x 2 & also has a high-pass crossover option.

          The KTP-455U won’t need very large power wire so that’s another plus. Both amps are class D so they’re around 84% efficient and won’t draw as much current/you can use a smaller wire gauge typically.

          2. Yes, ideally it’s best to at least ground the amps to a single point, although even if you try to do things “perfectly” you can still get ground loop noise. It happens.

          I would say since you’re going to use distribution blocks anyway, just run the amps to the ground block and then out with a single ground wire to a good ground point such as:

          • Seatbelt bolt location (brass/finished bare metal bolt to the body)
          • Another clean metal bolt or screw on the body
          • By using a self-tapping metal screw and cordless drill (my preferred option as it’s fast, easy, and works basically 100% of the time). This also lets you find many places closer which is important if the ground wire is short. Often times many in wiring kits are 3-5 ft long etc.

          In all cases I would use a good quality crimp ring terminal on the ground wire. Amp wiring kits include these and make installation a lot easier.

          3. You won’t need to spend a ton on wire or terminal blocks. In your case I think you’d be fine using 4 or 2 gauge in and 8 gauge out.

          You can do it this way to save costs:

          • Get a good quality amp kit like this one, to run to the dist. blocks: KnuConceptz 4 gauge kit
          • Get enough additional power, ground, and remote wire to go each amp. You can buy this by the foot or on rolls reasonably priced.
          • Some good quality/good value dist blocks are these here: InstallGear 4/8/10 ga. blocks

          4. That’s a good idea about running your wire in the doors! Good thinking. You can also straighten a thin coat hanger and bend the end in a round loop so it won’t snag and use that, too. :)

          Have a good Saturday!

  6. I have a Sony MEX N4200BT so do I run the rca cables from the radio to the amp and use some speaker wire from the speakers that’s in the doors to the amp? I ran the power from the cars batter to the amp and the ground from the chassis of the car to the amp just wanted to know about the speakers and I got the remote turn on wire ran from the aftermarket deck to the amp just was wondering how do I get the speakers to the amp because I’m new at this?

    • Hi Donzel. Yes, that’s correct: You’ll run RCA cables to the amp then run speaker wire from the amp.

      However, it’s MUCH easier to just run the speaker wire from the amp to the factory speaker wiring where the original radio was. This works if you don’t have a factory amped system.

      Usually what works best is using a stereo harness adapter to connect power for your Sony, then just connect the amp’s speaker wiring to the harness adapter’s speaker wiring (they’re labeled and color-coded so you’ll know which wire is which).

      Really it should be very straightforward in most cases. Just be sure to plan for getting enough speaker wire. I would measure the length from where you’ll put the amp to the center of the dash, then multiply x 4 to find out how much.

      Usually you’ll want to round up a bit to be sure you don’t come up short just in case.

  7. current 4 channel amps do not the list the output of the channel i.e., RF/LF, RR/LR. Besides trail and error is there anyway to know which output is driven by which input?

    • Hi Mike. That’s odd that your amp doesn’t have its outputs marked, but I’ve seen that before.

      Generally it’s inputs #1/2 = Left front, right front, and inputs #3/4 = Left rear, right rear if the RCAs are numbered. Otherwise, yes it’s trial and error if you don’t still have the owner’s manual with the speaker connection diagram in it.

  8. You have a very nice write up, very easy to understand. I was wondering if you could help me out with my situation. I have a 2006 Tahoe Z71 with Bose and Onstar. I’ve replaced the headunit with a Pioneer and the Pac Radio Pro 5 wiring harness, added two 12’s and an amp, and replaced door speakers with some NVX coaxials. Everything has been fine. However, I still wanted to add more power to the door speakers. So, I ran new speaker wire through all the doors directly from the speakers to the 4 channel amp. I add power and ground distribution blocks. After everything was finished and cut on the subs are working fine and the only speakers working are the tweeters in the A and D pillars, which I did not touch. So I’m lead to believe it must have something to do with the Bose amp or something similar. Any suggestions or places to point me in the right direction?

    • Hi Kayla & I’m glad you like the article!

      I’m not 100% clear on your installation and problem. Did you keep the Bose amp originally and replaced the door speakers…then added the 4 channel amp/wired directly to the doors later?

      The first thing I would do is to make sure the 4 channel amp is working right. If you’ve wired it directly to the new (NVX) door speakers correctly and the amp is ok, there shouldn’t be a problem.

      I would disconnect the door speaker wiring from the amp and use a test speaker right at it to check it. Also check to make 100% sure you have a good ground, +12V, and remote connection. If that’s all good then check the wiring to the speakers & make sure you get close to 4 ohms for each pair of speaker wire.

      It sounds like you’re just wanting to bypass the Bose system and drive the door speakers directly. That shouldn’t be a problem if the amp is ok and wiring is good.

  9. Hi after reading what you wrote I’m a little confused about the speakers wire set up. I have an aftermarket Enon G2110F with Qpower 300 watt front speakers and Qpower 700 watt rear speakers ( cheap I know but they sound bad ) and have a crunch 1000.4 channel amp I want to install. my question is are you say to run the speaker wires from the amp straight from the amp to back of the head unit? if so do I still leave the factory wires hooked up to my speakers? could I also just run speaker wires from the speakers to the amp? I’, sorry I’m new to this so any help you can give would be very much appreciated. Thank You.

    • Hello Tom and I’m sorry I somehow missed your comment some time ago. The comment system doesn’t always work right, unfortunately. :( I’ll reply in case you haven’t found an answer to your question still.

      You can definitely run wire to each speaker from the amp and in some cases you have to (bad factory wiring, bypassing a factory amp, etc). However, it’s usually fine and a LOT easier to leave the factory wiring in place and connect to it behind the head unit in the dash.


  10. Great article. Very helpful. Can you assist in a suggestion for the following marine installation (all 4 ohm)….replacing radio with a 4 channel head unit (MOFSET 240Watts …60×4 channel..And replacing amp with an 8 channel Rockville RXM8BTW.

    Installed speakers are….Six speakers 8in 100W/300 Peak Watts….One Subwoofer 10 In. 150W/300 Peak Watts. I also have the original 2 channel amp. Should I ditch the old amp or can I use it to drive the sub-woofer? or it it too powerful? Let me know your thoughts. Thanks Rex

    • Hi Rex how are you? I’m glad you found my article helpful! (Note: I edited your comment to keep it small)

      If you’re planning on using the RXM8BTW for six speakers + one subwoofer that’s great. I would just use that amp for all of them.

      However, it gets a little bit more complicated since all channels #5-8 use the same crossover, it appears from the manual. That means you’ll want to connect 4 of your 6 8″ full-range speakers in parallel for channels 1-2, and one speaker each on channels 3 & 4.

      Then you’d connect your subwoofer bridged on channels 5/6 or 7/8 and set the crossover to low pass. Unless you just want a lot more power for the subwoofer I think you’ll be fine using only the Rockville amp.

      So to summarize using it like this should work:

      – Channels 1-2: 4 speakers connected, 2 in parallel to each channel
      – Channels 3-4: 2 speakers connected: 1 each per channel
      – Channels 5 & 6 or 7 & 8: Bridged to the subwoofer


  11. Great article. I have a question. I’m hooking up an old Rockford 4.6x amp to an older vehicle. The amp has both high level and low level inputs. The headunit only has 2 channels and no rca outputs.

    I would like to use all 4 channels on the amplifier in order to use the built in crossovers for components on 2 channels and the 8″ sub on the other 2. On the amplifier my high level inputs only have 3 connections for each channel. They are labeled L, com, and R.

    All videos I have watched showing this amp have 5 connections L+,L-, com, R+,R-. Not sure why mine is different. Any suggestions on how to use this setup. My other question is would I be able to use a Line level convertor and use rca Y adapters off of it to send signal to all 4 channels

    • Good morning, Mike! I’m glad you enjoyed the article.

      That’s interesting about the amp you have not having the same high-level inputs as the others. Maybe it’s a short-run production model you have that they changed later.

      At any rate, to answer your questions:

      1. You could try using the L+, COM, & R+ high level inputs, and you’d need to connect both speaker negative leads to the COM connection. However if it were me I’d use a decent line level adapter instead.

      2. Yes, definitely you can use a 2-channel line level adapter and then just go from the RCA jacks to the amp with inexpensive Y adapters if you like.

      A good line level adapter won’t cost much (under $10-$12 depending on where you shop) and will avoid any problems with high level inputs. You could run a pair of RCA cables to the amp and then connect the Y adapters there if you want (as opposed to running a 4 channel RCA cable to the amp)

      Thanks for dropping by!

  12. Hi Marty, What do you think about the Pioneer GM-D8704. This seems to be in my budget and I am keen on getting this amplifier instead of Pioneer GM-D9705 – which you have reviewed and recommended. Please let me know about Pioneer GM-D8704. Thank you.

    • Hi Sam. I would go for it, and I’m sure you’ll like it just as much as the 5 channel model.

      It’s great that you still have an included bass remote like the GM-D9705 in case you bridge it to drive subwoofers.

      It’s a nice amp. I really like how compact they are, too.

  13. Hi Marty, I have a JL XD600/6 amp powering JL front door speakers in my 2015 Ford van (there are no rear speakers or unused rear speaker feed wires behind the deck. I’m using the standard deck and using a 2 channel line level converter. I’ve cut the speaker wires behind the deck and ran them to the LLC and then RCA into the amp, then wires from the door speakers run to channel 1 & 2 screw downs on the amp.

    I have a non-powered 12″ JL sub woofer I want to add to the system bridged on channel 3 & 4 screw downs. How will I get a signal to the sub woofer? Should I get a 4 channel LLC and split the front speaker feed before it goes into the LLC?

    Many thanks!!

    • Hi James. The great news is that you don’t need anything else.

      Just set the XD600/6’s input switch to the 2ch. mode and all 6 channels will be fed a signal from the 2 channels you have.

      • Hi Marty

        Thanks for the brief explanation.
        I have managrd to connect up everything in order.
        HeadUnit = DEH-X4750BT
        Amp= Targa da Warrior (5800W)
        Pioneer 600W (6×9)
        and a Pioneer 12” Sub (bridged on channel 3&4)

        Now I have received XTX Da Brat Spilts for front doors. How do I hook them up on the amp. Or how would I bridge the subwoofers if I used channel 3&4 for the spilts.

        Please and thank you

        • Well, I can’t really offer much advice with the specific amp model number, sorry. It’s very important to be specific when mentioning an amp or other components.

          However, if it’s 2 ohm stable in stereo mode and if it has sufficient power per channel (it’s not really a 5800W amp, more like 75W-100W RMS per channel) you can connect the component speakers and 6x9s in parallel on the front channels then bridge the rear channels for the subwoofer.

          You’ll lose a front/rear fader doing that, but you can drive all speakers that way. If using the front and rear channels for speakers you can’t drive the subwoofer properly and will need a 2nd amp (or use a single 5 channel amp).

  14. Nice write up what I can’t understand I got a pioneer sb100something forget anyway the hu has 6rca output now I just got boss t1004 riot 4channel amp now from the hu speakers wire harness do I still use them cause when I wired up the amp I’m getting wining sound from the front and the rear speakers I look at your diagram don’t understand it

    • Hi Stephen. I don’t understand your question 100%, but it sounds like you’re saying that you have a whining noise like “alternator whine” after connecting the amp using RCAs. Is that right?

      Here are a few notes:

      – Alternator whine (ground loop noise) is a pain to fix, and is happens more often with cheaper amps like the Boss. Otherwise you may need a ground loop isolator (for RCAs).
      – You could try connecting the speaker outputs to the inputs on the amp instead of the RCAs, and it may fix that, yes. (Don’t use both the RCAs and speaker leads at the same time. You can damage your head unit or amp)

      I hope this helps. :)

  15. Hi Marty, thanks for taking the time to help us all. I’ve installed a 4channel and using two RCA cables to power my four speakers front and back seat area say, I’m hoping too connect a pair of 6x9s now but not sure where they wire too? Daz. Happy new year 2020 btw

    • Hi there Darren & Happy New Year to you, too!

      Basically, if you want to use all 6 speakers you’ll need to connect 2 pairs in parallel on the amp. To do that, the amp needs to be 2 ohm capable (else it can’t handle the load). If your amp isn’t 2 ohm capable, let me know.

      It depends on where you’re going to put the 6x9s. You kind of have to choose based on your setup and the speaker outputs. If you need separate level control (separate gain control) for the 6x9s then use them alone on the front or rear channels.

      If they’re going to be mounted closer to the rear I’d say connect them in parallel to the rear speakers. This way even though you can’t adjust the 6×9’s output level separately at least you still have a front/rear fader possible on the amp.

        • Hi Marty am from Mauritius and have a question concerning wiring.
          I have a Pioneer GM D8604 amplifier. Can i run my 2 rear 6×9 speakers (80w nom/450w max) on bridged and my 2 front 16cms speakers + 2 tweeters together on the remaining 2 channels? Or can you suggest how I should do the wiring please?
          Hope to hear from you soon. Cheers!

          • Hi Ben. Bridging 2 of your 4 channels is possible for driving your 6x9s, however it really doesn’t make sense to do so. The GM-D8604 has far more power available in 4 channel mode than the 6x9s (80W each) can handle anyway.

            Your particular amp can handle a lower load than some other amps, so you can (1) run both the 6x9s and the tweeters off of 2 channels, or (2) run the tweeters and the 6x9s off of front/rear channels.

            I would use option #2, as you’ll have independent level controls for the speaker output level plus the ability to choose separate crossovers if needed for the tweeters vs main speakers.

            You can always change the setup later if you decide to bridge 2 channels for adding a subwoofer.

            Thanks. :)

  16. Marty, I’ve read your articles on wiring amps + read a lot of other people’s questions, still I haven’t came across the small issue I’m having, or most likely not understanding. When running speaker wire from the amp to the wiring harness behind the radio. Do i run the speaker wire from the amp to the harness that came with my aftermarket HU, or do i run the speaker wire from the amp to the factory wiring (in my case the Metra harness kit)?
    I’m just confused because both harness’s, aftermarket HU & Metra both have speaker wire.
    I hope you can help me out with this or have the time to. Thank You

    • Good morning, Melissa.

      In this case (since you would like to drive the speakers from the amp) you’ll run the wire from the amp to the Metra harness. This avoids having to cut the factory wiring. *[Note: For installations, I use crimp connectors and a crimp tool (available affordably at many stores) to make a reliable connection unlike twisting it & covering with tape.]

      You would only connect it to the head unit’s wiring (speaker outputs) if you were connecting the head unit to the speaker-level inputs of an amp instead of RCA cables for the signals.

      By the way, be sure to tape off or use crimp connectors to protect the head unit’s bare speaker wiring from shorts to each other or the vehicle’s body. A short can permanently damage the output stages of the head unit.

      I hope this helps! :)

  17. Hey Marty – You rock, thanks for the great info.

    I’m installing a Pioneer DMH-C2550NEX head unit in an old Land Rover with no previous stereo. I’ve got a new powered sub and a separate four channel amp.

    Do I gain anything by connecting two pairs, say the front, to the head unit and the rear speakers to the amp? It feels like by just using the amp I’m wasting the built in amplification?

    • Hi, David! Yes, by using an external amp you’ll get (all things considered) much better power, volume, and sound quality for the speakers. That assumes, however, the speakers are good enough to hear the difference. If they’re poor-quality single-cone speakers for example you wouldn’t notice it much – but you’d have more volume capability, at least.

      The Pioneer you mentioned is very nice but the “50 W x 4” power output listed is misleading. In-dash head units can’t produce more than 15-18W RMS per channel. So even a decent quality amp can greatly outperform them.

      I would say it depends on your goals, but speaking from experience, using a good amp to drive decent quality speakers is worth the effort.

      If you only want medium listening levels and don’t care about the sound quality as much, then you can stick with the Pioneer’s speakers outputs.

  18. Hey marty,
    Just a quick question I have a 4 channel amp and am planning on running the front and rear speakers through it.
    Can i run just the 2 RCA cables from head unit to amp and then wire the speakers to the amp or do I need to do both as in
    Run RCA cables from head unit to the amp and run speaker wire from head unit to amp then run the speaker wire from the amp to the speakers themself
    I Already have a set of RCA running to a single channel amp thats running the sup but my head unit has the other 2 ports for front and rear, Just not sure if i have to run both or just the RCA cables.
    If you could let me know that would be muchly appreciated as im a bit stuck

    • HI Richard. You would (ideally) add a 2nd pair of RCA cables to the amp so you can use the front/rear fader. You can get by with just the one pair you have now if you don’t need a fader. In that case you could use Y adapters at the amp or if your amp has a 2/4 ch. input switch.

      Don’t ever use an amp’s speaker inputs and RCA inputs at the same time: only one or the other (RCA inputs are best). If you connect speaker inputs and RCA inputs too it can damage the head unit.

      So you would 1) run RCAs from the head unit to the amp and 2) run speaker wire from the amp to the speakers or factory speaker wiring in the dash, depending on your installation.

      I hope this helps!

  19. Hi Marty,

    Just leaving some feedback here for your attention and that of other’s visiting your site.

    Marty was extremely helpful right from the start.
    At first I wasn’t very optimistic about receiving a reply to my email, especially as I am from the UK.
    To my delight I received a reply the very next day. Can’t say the same for the audio companies based closer to home.

    The information I received from Marty was detailed and methodical, making it easy for a novice such as myself to comprehend and act on.
    Furthermore, I sent a second email requesting more details about the setup i wished to pursue, and Marty once again willingly responded to a number of my questions.
    Not only can I now start work on my car audio system, but my understanding on the subject has tremendously improved, thanks to Marty.

    To other’s reading this feedback, you have my word that Marty is somewhat of an audio samaritan.
    Great guy.

    Once again Marty, thank you ever so much for your help.

    Best regards,


  20. Good Day

    I am hoping you can assist me. I am struggling with the following issue for days on end, and my car audio install is still not working right. I am installing a Phoenix Gold 4ch amp with 2 Pioneer 6×9″ speakers on a back board in my 2018 Honda Fit Sport using a passive LOC so I can keep my stock head unit. I have all of the wires run and have checked to make sure they are all wired correctly that I know of. I have the rear speakers hooked up to my LOC then I have a set of RCA’s running to my amp. The left output on loc, which i’m assuming is where the problem is coming from is not working while the left rear speaker still works. All of my speakers work if I move a working rca to each individual input on my amp though even if i use the left rca cabl. I have tried switching out my RCA wires completely as well and it didn’t fix the problem. All of my gain adjustments are turned halfway on the LOC and amp. If i change the sound to the left side of my car on my head unit i can hear very faint almost no sound coming from the speakers. another weird thing is that if i touch my left rca to the inputs on my amp i can hear audible sound (but still very quiet) coming out of the speakers, but as soon as i plug it in i can’t hear anything. sorry if i made this confusing, but i’m trying to give all of the details. any help would be great!

    Kind Regards

    • Hello Colin and I’m sorry I somehow missed your comment. The comment system sometimes misses notifying me, unfortunately. :( I’ll reply in case you haven’t resolved this yet.

      I think your LOC may be defective – it’s definitely possible. You’ve ruled out the amp, which is good, as I was going to recommend doing that.

      If you can, try to get another LOC and keep the receipt in case you need to return it and try that. Some lower-quality LOCs are more prone to problems like you’re having than the ones with a better electronic design.


  21. I installed a 4 channel amp using the 2 pairs of rcas rcas but I have one problem when I use the fader on the head unit it seems as if fronts work with rears any suggestion,?

    • Hi there. If your amp has a 2/4 channel input switch, it should be set to “4.” That could explain what’s happening.

  22. Hi Marty, thanks for offering so much great information on your site. I have a question about the remote wire. I use a car stereo head unit (pioneer mvh-x380bt) that powers 4 speakers on an grilling island in my backyard. Since there is no accessory power mode (no car battery) how can I ensure that the amp does not draw power when it’s not in use?

    • Good morning, Ed, and I appreciate the “thanks” too.

      If you’re not using a car battery I assume you’re using an AC-DC power supply, is that right? If the power supply is always on, you can wire an on/off switch to the +12V output, then go to the Pioneer’s ACC wire to act much like an ignition switch on/off wire would.

      You mention an amp, so can you clarify if you’re using an amplifier also? If so wiring the Pioneer the way I mentioned then connecting the amp to the Pioneer’s remote-on wire would work.

      Optionally you could use an inexpensive relay timer board wired to turn the Pioneer’s ACC wire off after a set time once it’s switched on. That way it will turn itself off and if you forget it’s no problem.

      • Thanks for your reply! That’s correct I am introducing a 4-channel amp to the backyard set up. And the power source is an ac/dc power supply as you guessed. Based on your images I’ll now power the amp with the 12v line and use the remote lead from the amp to the Pioneer’s remote-on wire to power the head unit. Does this sound right?

        I also have just two RCA inputs in the back of the head unit so i ordered two all-male RCA y splitters to connect as you show in your diagram.

        • Hi Ed, yes that sounds right about the remote wire. Ok, sounds great and I hope you enjoy your music soon!


  23. Hey Marty,
    A very well written article… But I have a question… Trying to hook up an amp to my campervan stereo, but I have a continuous thumping like a very fast heartbeat when I turn the system on and try to use the stereo…. I am obviously doing something wrong lol

    I have a kenwood kdc-bt600u head h it, and at the moment I have the amp hooked up with 4 rca plugs to the 4 inputs on the amp… And then 4 speakers coming out of the amp… I Do still have the front speakers hooked up to the car stereo… Could that be the cause? I am not getting any audio from any of the 4 speakers coming out of the amp, only the factory door speakers…. It’s prob something very simple, but my brain is feeling fried tonight lol

    Any help would be appreciated.

    • Hi Mark. Thanks for the feedback & comment. I’ll message you at the email address you provided.

      Have a good day. :)

  24. Hi

    I have bought a Hertz hmr 10 for my boat, with 4 speaker rca. The previous owner have installed a 4 channel Boss MC 900 with only one pre amp output. How do I take advantage of both amps and how do I connect them? Is there any way of keeping fade control with this set up?


    • Hi Arnfinn. I’m not 100% clear on what you meant by “both amps” as you only mention one (the Boss) and also don’t clarify what the “one pre amp output” was referring to.

      Basically, yes if you connect both pairs of RCA outputs from the HMR 10 to the Boss you will have front & rear fader controls if you’ve got all 4 speaker outputs from the Boss amp in use. You can also use the speaker outputs of the HMR 10 at the same time, although they’re weaker and won’t have much power compared to an amplifier.

  25. Hi ya,

    Instead of LEft front, right front, left rear, and right rear, my Boss R1004, has the 4 RCA inputs labeled ch1, ch2, ch3 ,ch4 … I’m using male to male splitters from the two channel radio, and just want to make sure that i get them connected the same as your diagram above .. Please advise asap,


    • Hi there Paul. Typically channels 1 & 3 are left and 2 & 4 are right. So you’d connect your RCA splitters like this:

      Left channel: to 1 & 3
      Right channel: to 2 & 4

  26. so I hooked up the white with the splitter to channel 2 & 4, the red to channels 1 & 3 …. is that right ????

    • Actually it would be white (left) to channel 1 & 3, and red (right) to 3 & 4. On head units, often the white is labeled “left” or “L” and similar for the red RCA jack.

  27. Hi Marty!
    My head unit has 1red 1white RCA bought 2 Y adapter 2female 4male so base on your reply to previous inquiry 2Whites goes to 1&3 while 2Reds 2&4. Is this true?
    Thanks and keep safe!

    • Hi, Angelo! Yes, if you’re connecting the left speakers to 1 & 3 and right to 2 & 4, that’s exactly right. (Assuming your amp doesn’t have a 2/4 ch. input switch to do the same thing…not all amps do, sadly).

  28. Hi Marty, great article and the diagrams are easy to follow. I had a question about my planned setup. My receiver has 2 speaker outputs and 2 tweeter outputs. I will connect to a 4 channel amp and I will do that according to your diagram above. Only problem is how will I connect a self powered sub ? I’m using high level inputs since receiver has no RCA’s. The self powered sub needs 2 speaker inputs. Where should I tap ?

    Thanks in advance, Vic.

    • Hi Vic. Thanks for the feedback regarding the diagrams as I’m continually trying to do my best with those. This is a home receiver you’re mentioning, I assume?

      For the self-powered subwoofer, you’ll connect it to whichever speaker outputs have bass in the audio. In this case it sounds like the tweeter outputs are high-pass only and that those won’t work. If you’re also connecting an amp in addition to the self-powered sub, you should be able to connect both of those to the same speaker level outputs if you need to.

      That’s because speaker level inputs are usually very high impedance (high input resistance) and can be connected at the same time. Optionally, you can also use a line level converter to provide RCA outputs and use the RCA connection(s) if you like. I’ve got an example diagram you can see here.

  29. Hi Marty, Great article! Here is my project…
    I bought a Boat that had a sound system that was installed 15 years ago with a alpine pdx4.100 amp, Arc 2way powered crossover on the input of the amp, subwoffer, and external bass knob.
    My issue is one side of the amp is dead…so i bought a new alpine pdr v75,100w rms 5 channel amp to replace it …also I also bought a boss 3way powered crossover to replace that since it was 20 years old! …
    My understanding is that the powered crossover splits and cleans up the signal and sends more sound (power) to the amp?
    The install is pretty straight foward except the bass output on the 4.100 amp, the 2 lead wire on the bass output is channel 3&4….1 wire on on the + side is #3 and one wire on on the minus – side is #4…im assuming that might go to the external bass knob? I hope you follow me on this one…haha! I’ve just never seen that before.
    I also bought a SMD distortion detector to tweak the final insulation!
    Any input would be greatly appreciated!

    • Hi Bob. Powered crossovers used to be fairly common since back in the day, not all car amps had built-in crossover functions or they were more limited. Unless there’s something you’re doing that’s different than most people use, you probably don’t need an external electronic crossover at all. The amp should be able to do what you need already.

      Basically, that’s what they did/do: split the audio signal up. Not anything to do with cleaning up the sound. A few units were able to act as “line drivers” and help the signal yes, but that’s not usually important these days.

      Since the PDR-V75 has a dedicated subwoofer speaker output you’d wire your subwoofer wiring to that (no need to bridge channels like on the old amp). Also, be aware that your old bass knob probably won’t work with the PDR-V75 and you will most likely need to see about ordering one of those since it’s sold separately.

      I hope that helps! :)


Leave a Comment