How To Wire A 4 Channel Amp To 4 Speakers And A Sub: A Detailed Guide With Diagrams

4 channel amps are great and have a lot of flexibility for the most part. However, they’re intended for use with 4 speakers or 2 speakers and a sub – not both.

However, it is possible to wire a 4 channel amp to 4 speakers and a sub! I’ve put together some really detailed information to help make this as painless (and inexpensive) as possible.

Read on to find out how! There are plenty of detailed diagrams to guide you, too.

What you need to know first

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

Let’s get a few things out of the way before we go any further. To drive 4 speakers and a sub with a single 4-channel amp you’ll have to make a few compromises.

I’ll explain here what I mean:

  • You’ll likely have to give up front-rear fader control ability as you’re giving up 2 channels for the rear speakers to drive a sub (2 front/2 rear).
  • Most but not all car amps today can handle speaker loads down to 2 ohms. If yours doesn’t, you’ll need a work-around I’ll show you. You may need a few extra parts.
  • Driving 4 speakers from 2 channels means the speakers are sharing the amp’s power, so you’ll have less power available to each of those.

That being said, don’t worry too much! You can still enjoy the music you love with a nice-sounding 4 speaker + subwoofer system.

What does the minimum impedance (Ohms) rating mean for an amp?

Image showing the minimum speaker Ohms rating for Rockville RXA-F1 4 channel amp as an example

Image showing a typical 4 channel amplifier’s minimum speaker load (Ohms) rating. Most car amps today have a minimum of 2 ohms per channel in standard (stereo) use and 4 ohms minimum when bridged. Never run an amplifier with a speaker load that’s lower than the rating! Your amp will run hot and possibly become damaged.

Today’s 4 channel (and other) car amplifiers have a minimum speaker load they can handle. The speaker impedance or “Ohms” rating of a speaker (also called the speaker load) is the resistance to the flow of electrical current that the amplifier sees at the speaker terminals.

Amplifiers are designed to handle a minimum speaker load. The rating shown on the amp or in the owner’s manual serves as a warning.

If you connect a speaker load below the amp’s minimum rating it can get hot and even become permanently damaged at some point.

I’ve seen this happen when people try to “get more power” by incorrectly wiring speakers to an amp. Don’t do it! Burning out your amp’s output stages is not a nice surprise.

Minimum speaker loads for wiring a 4 channel amp to 4 speakers and a subwoofer

Diagram showing series and parallel speaker Ohms calculation examples

Diagram showing how a car amplifier’s Ohm rating works with speakers. Speakers are usually connected in series or parallel (well, really, most often in parallel) which affects the total resistance an amp will see. That’s important because amps are designed for a certain minimum speaker load (Ohms rating).

As I mentioned above, most car amps today can handle a 2 ohm load per stereo channel (left & right channels) and 4 ohms minimum when bridged to drive an amplifier (called “mono”).

The real answer, however, is that it depends on your amp’s ratings. Always be sure to check to be sure. To keep it simple, I’ll summarize what will work for almost all systems & amplifiers you’ll come across.

The amp wiring systems I’ll cover here

In this post I’ll cover 3 types of systems as that should cover almost all amps you’ll find:

  1. 4 channel amps with a minimum speaker load of 2 ohms in stereo, 4 ohms bridged (for the subwoofer)
  2. 4 channel amps with a minimum speaker load of 2 ohms in either stereo or bridged
  3. 4 channel amps with a minimum speaker load of 4 ohms

#3 is less common but it’s one you’ll run across. Maybe you’ve got an older amp that’s been sitting around unused. If so, you’ll be glad to know there’s a work-around that I’ve come up with that will let you wire your 4 speakers up without damaging your amp.

4 Channel Amp Wiring Examples

Here are the speaker wiring and speaker (Ohms) loads possible for nearly all amps you’ll run across. I’ll describe 3 main system setups which I’ll cover in detail.

System 1: 2 speakers (parallel wiring) to each front channel = 2 Ohms x 2 + 1 subwoofer wired for 4 Ohms on the rear channels bridged for more power. This is the first and best choice for most modern 4 channel amps.

System 2: 2 speakers in parallel to each front channel = 2 Ohms x 2 + 1 subwoofer wired for 4 or 2 Ohms on the rear channels bridged for more power. 4 channel amps that handle 2 ohms bridged are less common but they are out there.

System 3: 2 speakers on each front channel (parallel wiring) wired with extra parts for 4 ohms per channel + 1 subwoofer wired for 4 ohms minimum. Because these kinds of amps can’t handle a 2 ohm load, it’s a bit harder and needs a different approach.

Testing speaker ohms with a multimeter

Image showing an example of how to test speaker ohms with a multimeter

Shown: An example of how to measure speaker impedance (Ohms) with a multimeter. It’s a great way to know for 100% sure what kind of speakers you’re dealing with to avoid problems with your 4 channel amp.

Car stereo and home speaker speakers are very similar except for the impedance rating they use. A speaker’s impedance value, measured in Ohms, is just the total measurement of electrical resistance the amp will see from the speaker’s voice coil.

Partly due to tradition in the electronics world and partly due to various other electrical reasons car stereos are commonly rated at 4 ohms and home stereo speakers around 8 ohms.

The good thing is that all you really need to know is roughly what the resistance of a speaker is. If you can measure that you can tell what Ohms rating to go by!

How to measure speaker Ohms with a multimeter

Example image showing how to use multimeter probes on a speaker

To measure the Ohms (resistance) of a speaker’s voice coil, hold the meter probes to the speaker terminals, making sure to keep firm contact to bare metal Paint, insulation, dirt, and solder flux can mess up your reading otherwise.

For example, we usually have a label on a speaker telling us if it’s 2 ohms, 4 ohms, and so forth. However, as crazy as it sounds, some speakers don’t!

That’s why it’s excellent to have a multimeter handy – you can find out 100% for sure.

Measuring speaker Ohms with a multimeter
  1. Set the multimeter to the Ohms setting. If the meter has an auto-ranging function you should be fine. Otherwise, set it to the lowest setting like the 10 Ohms or 200 Ohms range, etc.
  2. With the speaker disconnected, touch the speaker terminals with the meter probes. Be sure to touch bare metal on the terminals and make good contact.
  3. Read the measured value. The general range will tell you the Ohms rating of the speaker (Example: 3.6 ohms resistance would mean a 4 ohm speaker)

It’s important to be sure you’re not measuring across substances that can interfere with your measurement.

Things like the following can cause problems (I have seen this happen many times!):

  • Leftover solder flux or solder coating from manufacturing
  • Heavy oxidation
  • Heavy dirt, dusty, or other contaminants that build up over time
  • Paint or other coatings that don’t conduct electricity

If in doubt, you can rub them gently with a bit of sandpaper or even scratch the meter probes against the terminals to make better electrical contact.

Note: If a speaker is “blown” or burned out from abuse or physical damage to the voice coil you’ll never get a reading. That’s because for blown speakers the voice coil no longer has a complete electrical path you can measure.

Multimeters show an open circuit condition as “infinite” Ohms, which just means there’s no reading to be made.

Speakers don’t measure exactly 4 or 8 ohms!

Car and home speakers are rated by their general Ohms (impedance) rating. For example, 2, 4, and 8 ohm speakers are never measure exactly with those Ohm measurements.

That’s because each speaker’s design is a bit different from the next. The resistance you measure from a speaker is due to the voice coil’s resistance thanks to the long wire it’s made of.

Here’s an example chart to help you know what to expect when measuring speakers.

Speaker Rating Typical Measurements
2 Ohms 1-1.8 Ohms
4 Ohms 3.2-3.6 Ohms
8 Ohms 6 Ohms or more
16 Ohms 12 Ohms or more

As you can see, you won’t measure exactly 4 ohms for a 4 ohm speaker. It will be in the general range and close to its advertised rating, however.

What is “bridging” an amp? Why is this best for driving a subwoofer?

Diagram showing a 4 channel car amplifier bridged to 2 channels

Shown: Example of a 4-channel amp bridged to 2 channels.

Bridged mode (mono mode) is a built-in amplifier 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).

When this happens the result is that you’ll get substantially more power with them working together than you would with one channel alone.

Bridged mode is a flexible way to get more power from 2 channels (in this case the rear channels, for example). That’s especially important because subwoofers are big, heavy speakers that need more power than small speakers to produce the bass sound you want.

DIAGRAM – How to wire a 4 channel amp to 4 speakers and a sub

Note: Most standard aftermarket car speakers are 4 ohms each so I’ll use that assumption for my diagram. Always be sure to check your speakers before you wire them to your amp to be sure they’re compatible.

(Or click on the image to enlarge & zoom)

Detailed diagram for how to wire a 4 channel amp to 4 speakers and a subwoofer

Using power resistors for harder installations (4 ohm min. amps)

Image showing examples of higher power resistors (4 ohms) for use with speakers

Shown: High power resistors that can be used with a 4 channel amp when adding more speakers. Using these will allow you to keep the total speaker load (speaker Ohms the amp sees) to a safe level so the amp won’t get damaged. They’re inexpensive and are easy to use.

Power resistors are larger versions of the resistors used in many electronic products. Unlike their smaller siblings, they’re designed to be able to handle a large amount of heat.

Because of this, they’re a great way to deal with more difficult speaker and amp systems. In example #3 I showed you earlier, it’s not possible to use two 4 ohm speakers in parallel with an amp that can’t handle 2 ohm loads.

We can use 1 large resistor for each speaker as a work-around for this.

This workaround won’t be necessary for most modern car amps. However, since a few amps out there can’t handle 2 ohm loads (especially older amps you might have that you’d like to use) I’ve included this just in case.

Diagram showing how to wire speakers with power resistors for 4 ohms total

In the case of a car amplifier that can’t go below 4 ohms per channel, there’s no other way. However, if we add one 4 ohm power resistor in series with each speaker we can use the math to our advantage.

By doing so, we’ll end up with two 8 ohms measurements in parallel which will give us a nice, safe 4 ohms per channel!

However, you’ll want to buy the right kind of resistor. I recommend at least 25 watt (25W) 4 ohm resistors. While you won’t find them in many local stores, the good news is that they’re affordable. I’ve used them many times for speaker problem-solving.

I’ve used some like these over at Amazon.

How to get around the lack of a front/rear fader

As I mentioned at the beginning, if you’re using a 4 channel amp to drive both 4 speakers and a subwoofer, you’re going to have to make compromises. There’s simply no way around it.

The biggest one that comes to mind is losing the front/rear fader control. However, I’ve come up with a sort of solution that helps a bit!

By adding inline resistors to the rear speakers you can drop their volume and it acts as a “fader” already. You can use an L-pad (speaker volume attenuation) site like this one here to calculate resistor values for you.

I’ve already done the work for you, and here’s a great example. If you’re wiring 4 speakers and a subwoofer to a 4 channel amp, by adding 60 ohm resistors to the rear speakers you’ll drop the volume by 24dB (decibels).

The result will be that the sound is “faded” to the front and the rear speakers won’t be too loud.

Image showing to how to create a fader to rear speakers using resistors

Following the example I’ve provided here in the diagram above it’s pretty easy. You’ll need to pick up some 15W-20W (or higher) resistors. I recommend about 60 Ohms as it will give a volume reduction of 24dB.

That should be enough in most cases: Not totally silent in the rear, but most of the volume towards the front speakers.

What crossover settings should I use on my 4 channel amp?

Close up image of a car amp crossover controls

As most modern car amplifiers include very nice optional crossovers, for good sound it’s smart to take advantage of those.

Here are some good recommendations for the 4 main speakers and the subwoofer:

Speaker Crossover Settings
4 main speakers Flat (crossover off) or 56-60Hz high pass
Subwoofer 80Hz low pass

By using a high-pass filter for the 4 main speakers you can crank the volume when you want for more power & sound before distortion happens. When using a subwoofer, it’s really important to block vocals and upper-frequency music from getting to your sub.

The idea is to get “pure” bass sound as that’s what subwoofers are best suited for: Just purely producing great-sounding bass you’ll love.

What if my amp can’t be bridged?

Image with diagram of how to bridge an amplifier

While it’s true that nearly all amps with any “real” power today can be bridged from 2 channels to 1 channel (called “mono”, or bridging) for more power, some can’t. That’s especially the case for some older “old school” amps you might have in your closet but still like to use.

In that case, unfortunately, you’re really limited. Sorry! You have just a few options:

    1. Buy another small amp just for the subwoofer/subwoofers
  1. Run one small subwoofer from each of the rear channels

The problem with option #2 is that subwoofers need a lot more power to drive them well and sound good. There’s just no way around it.

8″ subwoofers are an option or a dual 4 ohm voice coil subwoofer could be used. That way you can safely drive each channel with a 4 ohm load even older amps can handle. These days, though, it’s usually easier just to get a cheap budget amp and avoid the headaches.

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

If your stereo doesn’t have output channels that’s ok! You can still connect a head unit car stereo with only 2 channels (left and right) to a 4 channel amp easily. In most cases, you only need 2 RCA Y adapter cables. The head unit’s left channel RCA jack is connected to the left front and left rear amp inputs. Then the same for the right channels. If using speaker level inputs on the amp, use the connections shown above. NOTE!: Use only ONE of the two connections shown. Never connect both the speaker level and RCA jacks at the same time – speaker level signals can damage your head unit’s RCA outputs.

If you’re wanting to install a 4 channel amp for 4 speakers and a subwoofer but only have 2 stereo channels available, that’s ok.

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

RCA y adapter cable image

All you need is a decent quality pair (2 total) 1 female to 2 male RCA “Y” adapters like these inexpensive ones from Amazon.

The sound quality will be exactly the same. Modern car amps are designed in a way such that all 4 inputs will get the same signal and there won’t be any problems.

After connecting the stereo to the amp, you’ll need to adjust the gain controls for both the 4 main speakers and the subwoofer output. My advice is to use a high-quality music track you know well already so you can easily tell when music sounds correct.

Additional suggestions & parts you may need

An amp wiring kit like this one will make your life easier! A a great (but affordable) amp wiring kit like this Belva 8-gauge complete kit includes not just the basics but a lot more. You’ll also need to pick up a 2nd pair of RCA cables (if using them) and maybe some extra speaker wire, too.

I can’t stress enough how important it is to be ready to install your 4 channel amp. While there are several ways you can go about it, wasting gas, time, and getting stressed out isn’t worth the headache.

It’s a lot better to start on the right foot and be ready at installation time. My advice is to pick up a good amp wiring kit and the tools you need beforehand.

I’ve also got some great guides ready, too, if you’d like more ideas:

Need advice on finding the right installation wiring? Check out my post with some of the best wiring kits for the money here. You’ll not just save a few dollars but avoid getting ripped off on fake wire gauges.

Your comments are welcome!

  1. I have a 4 channel 3000 watt amp. That can be bridge and run any ohm. I have 2 component speakers 4 ohm with crossover and tweeters. And 2 subs 4 ohm dvc. Can I wire this to this amp.? In parallel?

    110 Watts RMS x 4 @ 4 Ohm 1%THD+N 150 Watts RMS x 4 @ 2 Ohm 1% THD+N 300 Watts RMS x 2 @ 4 Ohm Bridged 1% THD+N Amp spec.

    Subs 600 rms
    Components are 200 watts paired.

    Rn 200 watts paired sorry

    • Hi, with a power rating of 150W x 4, it’s a 600W amp, not 3,000. Those specs like “peak” and “maximum” are misleading.

      At any rate, you can either use one DVC sub wired for 2 ohms, one per channel, or bridge the rear channels and wire both subs in series. If using it bridged you’ll have to wire them for 4 ohms total. That’s each wired for 2 Ohms then in series for 4 ohms total.

      Probably easier just to wire one per channel. Best regards.

  2. I bought a system that the previous owner had set up with an amp wired for bridged use to a subwoofer. The amp is a JL MHD600/4.
    There are 2 wires connected to the left rear (+) and 2 wires connected to the right rear (-).
    These 2 sets of wires are then connected to the subwoofer in what looks like a redundant setup.
    Any idea why this would be?

  3. All of this is a Pyle system.
    I have a very in expensive radio and amp.
    Amp is 400w and 4 or 8 ohm only
    And my radio ask to use only 4ohm speakers.
    I have a 4 ohm 8in sub, all of this is going in my pontoon.
    So do I use your wire set up #3 with the 4ohm resisters my amp does not have a bridge description
    PYLE Amp – PLMRA400

    • Hi Dean. That amplifier is not very good I’m afraid. You won’t be able to use it for good sound with a subwoofer. There’s no low pass crossover built in and in general, it’s a pretty poor amplifier compared to others on the market.

      You’ll need to either add a 2 channel bridgeable amp with a low pass feature or a mono sub amp to get the sound you want. In setup example #3 you’d want to use a low-pass filter for good sound and it also assumes the amp is bridgeable (99.9% of 4 channel amps these days are bridgeable).

      That Pyle amp will realistically provide less than 200 watts RMS total (about 45W/channel). As the Pyle amp isn’t bridgeable, you’re very limited as to what it can be used for. Rockville has some much better marine amps for the money with the features you’ll need for good sound but at a good price.

      Best regards!

      • Thanks Marty I’ll just use this amp for the 4 speakers. And I’ll pick up another 2ch for the sub.
        I guess while I’m at it I’ll throw in a second battery and maybe a solar charger cause I don’t know if the 50h- 4stroke will charge both.

  4. I have a 09 tacoma with a boss BV755BLC with Alpine tweeters in the upper doors that replaced the stock ones. Running 6×9 Infinity 9632 100 watts 3ohm in doors. Have 6.5″ Rockford Fosgate in rear doors along with the pioneer GM-A6704 4 channel 80 watt amp.

    I have the front speaker wires connected to channel A and the rear speaker wires connected to channel B. All the speaker wires are connected to a different terminal on back of the amp. Like the top 2 connections are one speaker left front. Under neath them are the other 2 left connections for rear.

    Same for other side next to them. I have 2 bottom connections for the front right underneath them is the other 2 connections for the right rear. I have no subwoofer.then on front side of amp I have my RCA cables from stereo connected to my channel A left and right and channel B left and right.

    When I first started adjusting the gains I turned them all down and raised the volumn on stereo up until distortion but never heard any. Cranked it to 40 and it was still clear. So I just backed off to 75% then moved the fader to front speakers and turned up gains till distortion then backed off.

    he gain is set a little more then half way. Did the same for rears. It’s always sounded good. I don’t use the Hpf freq switch or the lpf switch. I keep it on 4 channel and keep the base boost in the middle. Is this all connected right?

    I don’t use crossovers except on the tweeters that came with them. What I found weird was hearing no distortion on stereo with the gains off and stereo eq set in the middle. Is that right? Because the amp runs the stereo? You can reach me at jameswhomer@ this
    [Comment edited for paragraphs]

  5. I have a unique situation that I haven’t been able to find anywhere on the Net.
    I have a wrecking yard Monsoon amp from a 2004 Grand Am, and a Pontiac Head Unit from a 2000 Grand Am. The Head unit needs the Monsoon amp to work. (more on why I’m going with this setup later)
    Basically, the speaker connections from the head unit (4 speakers total, front and Rear/ Left & Right) are the INPUTS into the Monsoon amp. Then, within the amp it self it breaks out the speaker connections to 8 channels.
    -Front Tweeter right (+/-)
    -Front Tweeter Left (+/-)
    -Front Midrange right (+/-)
    -Front Midrange left (+/-)

    – Rear Tweeter Right (+/-)
    – Rear Tweeter Left (+/-)
    – Rear Subwoofer Right (+/-)
    – Rear Subwoofer Left (+/-)

    Essentially, the amp has a built in Crossover and splits out the frequencies to each output channel. I’ve tested each speaker pairing to verify that the Tweeter are only high frequencies (although very quiet) and the Woofer lower frequencies (with some mid-range bleed in there as well)

    I’m putting this in a car with 4 Speakers (2 front, 2 rear), and would like to ‘recombine’ the tweeter/Midrange channels for the Front and the Rear tweeter/subwoofer channels for the rear AS WELL as add a single Subwoofer. I can’t just take the right front tweeter and Midrange ‘+’ leads and connect them together and the same for the ‘-‘ leads to the other side of the 2 -way speaker. Doesn’t work…
    I also don’t want to add tweeters as then I’m altering the interior of the car, which I want to have stock looking as possible. (it’s a ’86 Fiero GT). This is why I want to use the Pontiac Head Unit as it fit’s the stock look and feel of the car (correct backlighting/’Pontiac’ badging etc..)

    Everything I read on the net is the opposite…putting 8 speakers in a 4 channel amp (which is simple)… I want to go backwards and ‘recombine’ everything WITHOUT spending more than I paid for both the Header Unit and Amp…

    Documentation for the Monsoon amp is next to nowhere…. I’ve tested to see if I can bridge the Woofer outputs (right side +/ Left side -) and it does work, but am unsure if the Amp is truly capable of Bridging.

    Is there a passive device that can ‘recombine’ the outputs from the Amplifier, or should I just connect the Front and Rear speakers to the front channel (in Parallel… apparently the Amp is rated for 2 ohms) and just use the rear for a Bridged Woofer and forget about the Tweeter connections all together? I feel I’d be missing out on some high end though by ignoring these outputs.

    Thanks in advance,


    • Hi, no, sorry what you’re wanting to do will require spending money and adding more complexity. Tf you’re not wanting to use separate tweeters & woofers as the original amp is designed for you can recombine the amp outputs using a device like an AudioControl LC6i then out to an aftermarket amplifier.

      A second option is using two 4 four channel aftermarket amplifiers then wire them in bridged mode (2 channels each speaker) to each front and rear speaker. The left & right inputs for each stereo channel pair will combine that way also.

      You’re better off using component speakers similar to how the amp was intended for. Or just skip it all and use an aftermarket amp and radio and eliminate the problem altogether. Best regards!

  6. I have 4 6×9 with 4 tweeters with 4 crossovers and would like to run a sub with a 1800 Boss amp. Is this possible? and how would that be wired?

      • Rockville RV68.2C speaker package. 4 6×9 speakers 4 tweeters 4 crossovers
        Boss PF1800 4 channel amp
        Skar twin coil 10″ sub

        • Hi, well you left the specs off of the subwoofer so I’ll have to speak in general terms in that case. You have somewhere around 120W per channel available with that amp which should be adequate.

          You’ll wire 2 pairs of speakers to each of the front channels. Then either one channel to each DVC coil *or* bridge the rear channels if the speaker Ohms of the subwoofer will meet the 4Ω min. requirement for the amp in bridged mode.

  7. Hello,

    I have a small question – I have 4 speakers and a 4 channel amp. The speakers are 100 watts rms. If I connect my speakers to ch 1 and ch 2 in parallel, it will require max of 200 watts rms to run them at its full potential right ?
    Also if I bridge my 3 and 4 channel to produce mono and connect a 4 ohms svc subwoofer, will the amp still be delivering 4 ohms or will it deliver 2 ohms ? I only have the speakers rn and deciding upon the sub and amp.

    • Hi, for the speakers wired in parallel, they’ll share whatever power output (RMS/continuous) that the amp is rated for. Your speakers are rated for *up to* 100W but that’s not required. Just a decent amount of power is needed at least (although it’s nice to have plenty of power available if you want to drive them at full capacity).

      Regarding bridging, well the question isn’t quite right. The amp doesn’t deliver impedance – the speaker impedance is what the amp “sees” or what affects how much power the amp can deliver.

      When bridged the amp will see whatever speaker Ohms load you have (in this case 4Ω). Bridged amps nearly always must be used with 4Ω at least. Best regards.

  8. hi I have a 4 speakers and 2 subs a 4 channel amp. it has a built in cross over and it’s A/B also I have a plug N play adapter so no splicing wires in car what is the best way to hook up????

    • Hi well it’s hard to answer without specifics but basically you will have to run the 4 speakers off of the front channels in parallel if the amp is 2 ohm rated. Then the subs either one per channel or in series depending on their impedance which you didn’t specify.

      Really though you’re not going to have a lot of power the subs and you’re better off adding a 2nd amp if possible for them. The power each sub gets will be whatever the amp’s power is per channel. Best regards.

  9. Hello, I have a 2009 Searay 270 Sundancer I just bought and was looking at the wiring of the stereo and would like your opinion on it.
    The head unit is a Sony CDX-H905IP and the amp is a Panasonic EAA0468. There are 2 speakers and a sub powered off the amp. It seems like it is wired wrong in my opinion.
    Off the head unit there is Rear/Sub RCA L/R out and a Front RCA L/R out. They are only using the Rear/Sub out with Y splitters/adapters going to the amp which are then plugged into the L/R rear and the L/R front RCA inputs of the amp. Then on the amp they have the sub Bridged off the rear speaker connections (which is normal) but they have the 2 speakers connected in parallel off of the left side instead of 1 speaker on the left and 1 speaker on the right. Thanks for your thoughts in advance.
    The system was working (at least playing music) but the 2 speakers quit and would just randomly start them stop. That’s why I looked into it. The crossovers were in HPF for both. When I put the crossover for the 2 speakers in Full they worked. Also when using the balance they only played in left since they were wired that way I believe. So I’m not getting stereo probably.

    • Hi Bob. I can’t find any amplifier with that number so I don’t think that’s the correct model number (?). At any rate, it sounds like you have a 2 channel amplifier and they attempted to make do with that which isn’t going to work out well for adding a subwoofer. Also, I’m not sure why someone set the crossover to high pass (HPF) as that’s definitely not correct.

      I would consider replacing the amp with a 4 channel model and use the (bridged) rear channels for the sub (LPF on) and the L/R on the front channels. You’ll have much better sound that way. You can use the HPF in that case for the front speakers in order to get even more volume without them distorting (set to about 56-60Hz HPF).

      Alternatively you could add a second amp just for the subwoofer. There are some good budget mono amps out there which are pretty small in size these days. Best regards.

  10. Hey Marty ,I’m working on 2 sundown 4 Chanel amps (4 by500 watts connecting to 12 ,8 ohm 140 rms speakes, what’s a safe but high power connection

    • Hi, to be clear you’re wanting to connect 12Ω and 8Ω speakers? How many of those? I’m not 100% clear on what you mean. I can tell you though that speakers above 4Ω are best connected directly to the speaker output terminals (not in series, etc.) because they’ll develop less power than 4 ohm speakers.

      If you only have a few speakers then bridging them would be the best if you’re using speakers above 4 ohms. Bridging will provide a higher output voltage and more power to higher Ohms speakers than otherwise is possible.

  11. amp—–2 Ohm Stero Stable Class A/B 4-Channel Amplifier
    RMS Power @ 4 Ω: 150 Watts x 4 Channels
    RMS Power @ 2 Ω: 250 Watts x 4 Channels
    RMS Power @ 4 Ω (Bridged): 500 Watts x 2 Channels
    would like to run 4 @ 250 rms
    2 8s mid. @275 rms 4 or 8 ohm
    2 6.5s mid. @250 rms 4 or 8 ohm
    1 10 mid. @300 rms 8 ohm Can this be accomplished???

    • Hi, you could parallel the 8″ and 6.5″ in pairs on the front channels which would leave you with 2 channels free. Hving just one 10″ midrange is unusual but it could be used on one rear channel or bridge the rear ones to drive it.

      It really depends on what you’re wanting to accomplish. If they’re not all going to be used for full range sound or bass, etc., it’ll be more complicated. Best regards.

  12. Hello Marty, thank you so much for this write up, you really clarified it for me.

    I just want to check to make sure

    I have a Sony xav7000 4ch head unit with built in amp, 4x fosgate 4ohm component speakers w/ a crossover & tweeter. & I’ve found a good deal on a sub I like that’s a 10” 4ohm SVC subwoofer.
    I’m just not sure if my amp falls under option 1 or 2? Since I’m reading that my XAV has a setting to change speaker impedance from 4ohm to 2ohm when wiring your speakers in parallel mode, what does this setting classify my amp as, & would it be ok channel 3/4 bridged using said sub??
    Thanks for being such a valuable resource & best regards!

    • Sorry for the multipost.
      Well so I found this guide from the manufacturer regarding my model:

      I was hoping you could do me a huge favor & maybe take a look/decipher some technicals for me before I waste any more recourses.
      So while it doesn’t mention bridging specifically anywhere, please correct me if I’m wrong, but do you think any of the references to the manners of connections & specific plurality of “subwoofer(s)” means bridging comparability?

      • Hi it doesn’t appear to be bridgeable, so you’re stuck with what it can provide unless you get a separate subwoofer amp which would work much better. However, my understanding is that you can wire the rear speaker positive leads together to the positive terminal of your SVC subwoofer, then likewise for the negative side. Then set the impedance option to 2Ω.

        Personally it’s not something I would do (wiring a subwoofer to a head unit) on the job for several reasons including avoiding potential problems with the head unit. Assuming all goes well, that’s only 90W RMS which probably won’t be enough power depending on the circumstances, although it’s enough to get some bass.

        I wouldn’t use less than 150W RMS with a 10″ or 12″ sub. But you can certainly try it out and see how it sounds then go from there.

        Have a good weekend & thanks for your kind words. :)

  13. Marty,

    On our boat, we have a current Fusion MS-RA55 headunit and I’m looking to add the Kicker 45KM654L (2 pairs) with the Kicker 48KMA3604 amp. I feel I will want to run this bridged to supply speakers with proper power, correct?

    If I wanted to add the Wet Sounds Stealth AS-10 to the system, is this possible? How do I provide the unit input from the headunit?


    • Hi,

      1. You’ll want to run the amp in 4 channel mode if you have 4 speakers. Bridged amps aren’t stable to 2 ohms so there’s no advantage to be gained in this case.
      2. Yes, as your head unit have 4 RCA outputs you can use those and use a “Y” adapter if you need to in order to connect to both the subwoofer and your amplifier.

      Best regards.

  14. Hi Marty,
    I have an 02 Chevy Silverado stock unit and just replaced, the stock speakers with like JVC’s front and rear. Still not enough bass. I’m really not into dumping a lot of money into a car stereo, and got a subwoofer from the local pawn shop. you know the ones that fit in the spare tire of a car. Anyway my thought was, run series from the rear speaker or both if possible, my concern is if I connect to one side or other won’t it affect the balance? And how do I remedy this? best possible way?

    • Hello Al. I’m assuming the subwoofer you bought has an amplifier built in? Because if not you’ll need to install an amplifier to drive it as well because an in-dash car stereo can’t drive a subwoofer.

      Regarding your question, it depends on the particular amplifier. If you’re using the speaker level inputs on an amplifier, some work fine for bass with only one channel connected and some don’t. It’s best to connect both the L & R channels to the amplifier inputs. Best regards.

  15. would this amp suffice for my purpose?
    BOSS Audio Systems R1004 4 Channel Car Amplifier – Riot Series, 400 Watts, Full Range, Class A/B, 2 Ohm Stable, IC (Integrated Circuit) Great for Car…

    • Hi there, Al. It would be ok for small speakers, yes. However, just be aware that the power ratings seem to be inflated. It’ll be somewhere around 33-35W RMS/channel for that amp, not up to 75W/channel as listed.

      That’s still enough to do the job with standard speakers, however. If you’re after more volume & power you’ll need to pick a different model though, so it depends on what your needs are.

      Best regards.

      • Thanks Marty.
        I’m on of those that are of the mindset that that is plenty of power for a car stereo as long as there is base to go along with it. by the way my speakers are rated 200 and 300 watts so i don’t any problems, Thanks for your help and advice.

  16. I have a JL400XD in my moto fairing, I want to wire Bridged Parallel to get most power I’m using 4- 4 Ohm speakers currently Have wired with FrontR + and RearR + on positive side of channel. 1, Front R neg and RearR neg on negative channel 2 Also Have Front L+ and Rear L+ on positive of channel 3 and finally Front L- and Rear L- on channel 4 negative I believe this makes a 2 ohm load sounds good just want to be sure im ok here

    • Hi Robert. It sounds like you’re saying you’re wriring the speakers for 2 ohms bridged which the XD400/4 doesn’t support according to the JL Audio specs. You’d simply wire one speaker to each channel.

      Based on their power ratings, you’d actually have less power available at 2Ω (100W/2) to each speakers versus wiring them for 4 ohms (75W/channel). RE, “Stereo, all channels driven: 75W RMS x 4 @ 4 ohms, 100W RMS x 4 @ 2 ohms” Best regards.

  17. My amp goes down to 2ohms for parallel connections is that st ill safe and would a speaker junction box for the connections be advisable for speaker connections and would this add to resistance? As I stated this is a stock radio/cd in my vehicle but speakers have been updated and I want to ad a single subwoofer as well

    • It depends on the impedance of the speakers you’re using. If the amp can handle down to 2 ohms, that’s two 4 ohm speakers wired in parallel. A speaker junction box is normally just one way to connect them electrically, but normally not needed for car audio.

      You’ll want at least one separate amp channel in order to drive a subwoofer with good, pure bass (low pass crossover).

  18. i have i nano amp rock series d rsk p 800.4dm
    80w x 4 at 4ohms
    160w x4 at 4ohms
    and 320w x 2 at 4ohms bridge
    for speakers i have 2 pairs of focal auditor + witch i believe they are 75w at 4ohms and for a subwooofer it a ds18 slc 8s 200rms at 4ohms single coil
    will this amp work for this speark and what setup you recommend

    EDIT: sorrry its 160w x4 at 2ohms

  19. I’m just getting into the whole sound system game but I’m on a budget. I’m trying to power 4 6×8 jbl speakers and a 12″ jbl sub. Do you recommend a good amp to power them all for a budget price?

    • Hi Moe. You have 3 options, ultimately: 1) use a 4 channel amp with the rear channels bridged (not front/rear fader), 2) use a 5 channel amp, or 3) use two amplifiers like a 4 ch. plus 2 ch. or mono amp.

      I think a decent/good 5 channel amp would be the best option and best value overall. Check out the Skar Audio RP-600.5 as it’s 60W x 4 + 200×1 which will be enough to get the job done. There are other budget 5 ch. amps as well such as Boss or Planet Audio but I can’t recommend them. Also their power ratings are not always honest.

      Using a 5 channel amp means you won’t have to give up the front/rear fade ability. You can also bridge the main channels if needed, too. Best regards.

  20. Hi Marty,

    I just thinking about this…

    I have amp which in chanell 1 and 2 are connected front speakers.. Also crossover between twitters and midbass… Speakers are 3 ohm impedance.. My amp is ready for 2 or 4 ohm impedance..
    Also on chanell 3 and 4 bridged i have subwoofer which have 400W RMS one voice coil…

    Question :

    1. So it is good idea connect front speakers with subwoofer i to one 4 chanell amp?

    2. On 3 and 4 chanell bridged so my amp delivering 400W RMS for my subwoofer which needs 400W RMS? I have set amp on 70% of his power.
    I want all of those 400W deliver for my subwoofer not only half or etc..

    3. And also i have 3 ohm speakers connected into my amp which is ready for 2 or 4 ohm and 3 ohm?? Or it is connected on 3 ohm approx 150W rms from amp for my speakers?

    My amp spec are :
    RMS power 4 ohm : 4x110W
    RMS power 2 ohm : 4x200W
    RMS power 4 ohm bridged : 2x400W

    My speakers are :
    130cm and 100W RMS
    3 ohm impedance

    My subwoofer is :
    400W RMS
    1 voice coil
    4 ohm impedance

    • Hi Mats.

      1. Yes, it’s fine to do that, they’re designed to be connected that way if you like as long as the impedance is at least the same or higher than what it can handle.

      2. The power depends on the model of amp you have and is listed in the specs, so in this case yes you can get up to 400W (if that’s the RMS/continuous power).

      3. Yes, the power will be somewhere around 150-160W if you’re using 3Ω speakers.

      Best regards.


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