How To Install A Subwoofer And Subwoofer Amp In Your Car – The DIY Guide With Diagrams

Installing a subwoofer in your car yourself feels great! It’s so much fun to finally enjoy the awesome bass you’ve been missing in your music.

I’ve seen a lot over the years as I’ve done hundreds of car audio installations – and unfortunately, I saw a lot of good people end up with a terrible sounding system or heard about them getting ripped off. I don’t want that to happen to you.

I’ve put together an extensive guide to help you get started along with buying information, diagrams, installation steps, and more. 

Infographic – How to install a subwoofer in your car

Infographic for how to install a subwoofer in your car

Before you get started

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

In order to help you understand the big picture I’ll explain the basic things we need for great sound and a successful installation:

Electrical connections:

  • +12V battery connection with a fuse
  • A good, solid connection to the car’s metal body
  • +12V “remote on” lead to turn the amplifier on or off with the stereo or ignition
  • An audio signal source (radio/head unit) for the amplifier
  • Wiring from the amp to the subwoofer

Subwoofer details:

  • A speaker made for producing heavy bass (subwoofer)
  • An enclosure designed for bass to install the subwoofer in (or a preassembled subwoofer box)
  • An amplifier with a low-pass crossover feature and enough power to drive your subwoofer (150W RMS or above is recommended)

In most vehicles, a +12V connection at the battery is relatively easy to find and route power wire to the amplifier mounting location you’ve chosen.

However, in today’s vehicles, it can be harder to find a +12V wire for the remote on connection that turns on and off with the factory stereo or the ignition switch (normally the accessory position).

This is because today’s vehicles have more wiring which is related to computerized signals and don’t use 12V. They’re often a lower voltage or are a data signal bus and can’t be used for this purpose.

There’s less time and frustration if you get the right parts and tools the first time so you don’t have to after you’ve already started. Try to get the basics you need first before starting.

As a side note, you can use a car subwoofer with a home stereo if you’re so inclined, too.

Planning time

Image of a young man working on car in garage

Try to allow enough time for daylight and to avoid rushing your work, especially if it’s your first time doing your own car audio installation. If you get stressed because of time you’re more likely to make mistakes and have to redo something later. Better to plan well or stop and pick back up the next day. If you can, however, borrowing a friend’s is a huge help.

Installing a subwoofer in your car is often hard work depending on the vehicle and what you’ll need to go through for installing and hiding the wire. If you’re adding a subwoofer to a factory system you should definitely prepare for extra work.

A good estimate is perhaps 3-5 hours or more for adding a subwoofer to an aftermarket stereo and 4.5+ hours for a factory system.

The right tools make all the difference! It’s worth it to wait a bit and get all the right tools together instead of struggling with the wrong ones.

You don’t have to spend a lot of money, but if you’re a careful shopper you can usually get most of what you need without going broke.

Most of them are basic tools and are relatively inexpensive. Just shop carefully and you’ll find good values.

Get the tools and supplies you need

Image of Scosche TK12A car stereo installation kitNeed an easy start? Consider picking up a car stereo installation kit like this Scosche KT12A budget kit from Amazon.

This is one of the single best steps. Without a doubt, buying the right amplifier, speaker enclosure, and subwoofer is critical for good bass sound.

The good news is that you have more options than ever these days!

Parts to gather before you begin

  • Amplifier wiring kit (see notes below) with fuse holder, remote wire, and connection accessories
  • Speaker wire for the subwoofer (and signal connections if using factory stereo)
  • Hand tools
  • Mounting brackets for mounting down the subwoofer box if needed
  • Cordless variable speed drill – not required but highly recommended
  • Good quality electrical tape (should say “UL Rated” on the inner roll)
  • Wire (zip) ties, small bag – 6″ or 8″ are great but others work well
  • A small package of 3/8″ length #8 self-tapping screws (if you have a drill)
  • Wire metal coat hanger (great for bending into a straight piece for pulling wire)

I’m a big fan of the Black & Decker cordless drills and they’ve done very well for me for installation jobs. Here's an excellent low-priced model I recommend from Amazon.

You might also consider planning ahead to upgrade your speakers to some better sounding ones while you’ve got your vehicle already apart, too.

Amp wiring kits

NVX XKIT42 4 ga amp wiring kitA good amplifier wiring kit like NVX True 4 Gauge AWG 100% OFC Amplifier Wiring Kit Without RCA Cable - XAPK4 includes a  fuse, fuse holder, subwoofer speaker wire, power cables, remote wire, zip ties, RCA cables, ring terminals, and cool accessories. They make your installation MUCH easier and help you avoid paying outrageous prices from local shops.

Amplifier wiring kits come in different price ranges and quality levels. Some only contain a fuse holder, fuse, power wire, ground wire, and the remote lead wire (typically an 18 gauge wire). Others also include RCA cables and speaker wire.

The best kits include installation accessories like ring terminals, zip ties, and sometimes wiring grommets.

I definitely recommend purchasing a kit that is complete. For the average amplifier, you don’t need to spend a huge amount of money for a good kit.

What you can expect to spend

If you shop wisely you can spend around $30 for a great 8 gauge kit and around $50-60 for a 4 gauge kit you’ll really love.

Note: Not all wiring is the same. Some misrepresent the wire size they contain and don’t actually contain pure copper wire or contain wire that is actually smaller than advertised but looks larger because of the wiring jacket.

Speaker wire

wire of 16 ga speaker wire

Don’t waste money on overpriced speaker wire. The main thing to remember is to buy quality wire – preferably a name brand type – with good insulation and good conductors. One wire is marked as the positive lead so you can connect it properly.

For an average subwoofer or pair of subwoofers, a small section of 16 or 14 gauge can work well. You can find 25 ft lengths or smaller for a good price.

You don’t need super-expensive brands, so don’t get talked into spending a lot of money. Just try to find a quality wire with enough length (normally on a roll) that’s priced fairly. Don’t spend excessive money on speaker wire as it’s a waste – you just need good wire.

Heads up! Speaker and power wire marked as “CCA” is not pure copper wire! Because of the rising cost of copper, manufacturers are now using copper-coated aluminum wire, which is lesser quality than pure copper wire (and less expensive).

For your speaker wire, it’s likely fine, but be aware when shopping. Sometimes the CCA note is in small print.

When connecting to a factory system with no RCA jacks, expect to also pick up a roll of small gauge wire (18 or 20 gauge is good) of sufficient length to go from the vehicle’s speaker wiring to the amplifier.

A 50 ft roll should work well for 2 pairs of speaker wire being run. If you’re wondering how much a good basic roll of wire costs, here's a good example of true copper speaker wire that's affordable from Amazon.

Amp selection

Pioneer GM-D9605 review test amp rack image

You don’t have to break the bank to get a good amp for your new audio system. Expect to spend around $100-$250 depending on the features and power you need.

This is very important but the great news is that these days most amps have the basic necessities for working with a subwoofer enclosure and producing good bass.

Remember that you can use both a single-channel (also called “monoblock”) amplifier or multi-channel amp that is bridged for more power.

Features you need for good bass are:

  • 150W RMS power for the subwoofer available (either a single amp channel or 2 bridged channels)
  • Low-pass crossover for passing only clean bass and no upper-range music
  • A mid to high-quality brand with good reviews
  • Speaker level inputs option (if using a factory stereo

Bridging an amplifier means wiring the speaker connection so that we take advantage of a built-in design feature which allows 2 amplifier channels to drive one speaker (or pair of speakers) for more power.

This typically allows 4 x the power of a single channel to be provided! (Always check the specifications to be sure of power available and the required speaker Ohms rating).

For the average person, an amplifier capable of producing 150W for use with a well-matched subwoofer and speaker is adequate. If you want real “thump” and heavy-hitting, loud bass, plan to spend more and get a model with more power.

Alpine MRV-F300 4 channel amp end viewModern car amplifiers like the Alpine MRV-F300 offer high or low-pass crossovers to block bass or upper-range music from being played as desired. The amp shown has adjustable frequency cutoffs to control what sound ranges are sent to speakers. The “Full” setting means all sounds are allowed to the speakers.

A low-pass crossover is a feature that will filter out upper-range sounds and will allow you to play only clean sounding bass. 

High pass crossover block bass and allow higher-range sounds like music to play while blocking bass that distorts small speakers.

Additional crossover options

Some also have added features like an adjustable crossover frequency (as opposed to a simple on/off switch) and a bass boost. Crossovers are a simple but incredibly helpful feature for getting the best sound and volume out of your system.

Regarding power, you can likely get by with less if using a small subwoofer (for example an 8″ or another small type of subwoofer in a premade enclosure).

For noticeably louder and better subwoofers, however, it’s best to buy the largest you can that will fit in the space you have.

Using multi-channel amps vs. single-channel (mono) amps

Both types of amplifiers have their pros and cons to consider.

If you plan to power

more speakers in the future and expand your stereo system, think about buying a 4-channel stereo. Even if you don’t use all 4 channels right now that’s fine – you can always use them later.

This leaves 2 channels to power front speakers and 2 you can use later for more speakers or bridge for driving a subwoofer.

Multi-channel amp pros and cons:

  • Flexible and great for multiple speaker systems
  • Lots of brand and models available
  • Can be used in 2, 4, and other channel modes (bridged)
  • Popular, so often many reviews are available
  • Tend to have lower power ratings
  • More power connections to deal with
  • May not be as compact as a mono amp

Mono amp pros and cons:

  • High higher power available for subwoofer use
  • Often can be as compact as or smaller than multi-channel amps
  • Simpler controls in many cases
  • Not flexible – useful only for subwoofers in most cases
  • Model choice and options tend to be more limited
  • Many are low-pass only, no full range possible

I recommend you buy a good quality 4-channel amp with 50W x 4 or 75W x 4 (at 4 ohms) that is bridgeable to 150W or more. You’ll have more flexibility in the future and won’t have to buy another amplifier.

It’s the best bet for the beginner and the average person. It’s always smart to plan ahead.

Subwoofer selection and things to know

Boss Audio CXX12 car subwoofer product image #1

When shopping for subwoofers, don’t go for the cheapest right away. Look for a good combination of price, power rating, and features. Good reviews are a must, too.

If you’re buying your electronics and subwoofer for the first time, it’s best generally to avoid buying an enclosure and subwoofer separately unless you know the recommended enclosure volume size (in cubic feet) for the subwoofer speaker or speaker pair.

Also, I recommend you buy a sealed enclosure as mismatching a subwoofer with the wrong vented box can result in terrible sound! I saw this many times, and it’s incredibly disappointing to see.

Not every subwoofer works with every box

I’ve done many speaker designs of various types, and here’s a simple explanation of why it matters: Every speaker has certain parameters that determine how it performs in certain types and sizes of speaker boxes.

If the speaker is not matched correctly, the sound produced can be far below what it is cable of.

This can result in “bottoming out” early (the speaker has little resistance to movement and begins to reach its limits when moving) or simply can’t produce bass sounds at a normal volume.

Your hard work will have been for nothing if that’s the case, and it feels terrible to work very hard only to get bad sound.

Example loaded car subwoofer enclosuresIt’s best to start with a subwoofer combo in which 1 or 2 subwoofers are correctly matched to the box. In most cases, a brand name box with speakers is designed specifically to work well with the speakers based on their particular characteristics. This is the most convenient option for some people. 

My advice is to buy a brand name pre-assembled (“preloaded”) or matched subwoofer speaker/box combo. It will pretty much guarantee you’ll get good sound.

If buying a preassembled box, you can’t also buy a vented (ported) model if you wish.

Ported speaker boxes generally have slightly less “tight” sound but can often play louder and deeper vs. a sealed box for the same amount of power. So it’s generally your preference.

Many small subwoofer combos are ported to get more sound from a small size.

Generally speaking, you’ll need to buy 4 Ohm subwoofers

Many amps, both single channel or bridged multi-channel amps, require a minimum speaker impedance (Ohm rating) of 4 Ohms, so bear this in mind when shopping. You can learn more about that here.

Consider buying a car powered subwoofer

A car powered subwoofer is one that is an all-in-one bass system made up of a special enclosure, matching subwoofer, and has an amplifier already built-in.

They’re easier to install than a separate amplifier/subwoofer system.

Additionally, they’re a great choice for people who may later change vehicles especially people who own leased cars. The total cost for a powered subwoofer vs. separate items may be lower, too!

Image of MTX AUDIO RTP8A powered subwoofer side viewA powered subwoofer is an all-in-one solution for subwoofer bass. Although many are extremely compact to fit in space-limited vehicles, some like this one offer bass nearly as good a more expensive amp & speaker box. Typically their overall cost is less or the same as buying the items separately. There’s also no amp to worry about mounting, too!

They do have drawbacks, however: while they offer a more convenient way to install and remove the audio system, they tend to be more likely to have lesser performance than by using a standard amp and box system.

Car powered subwoofers tend to be more oriented to solving the problem of limited space in a vehicle and may be more limited in their speaker size, amplifier power rating, and the bass volume they can produce.

Note that they’re generally great choices if you want good but not extremely loud bass in your vehicles.

Some models, however, feature larger speakers and high power built-in. I’ve covered this topic and show some great examples here.

Pro Tip
Whenever possible, if buying a powered subwoofer, get the largest model you can fit into the space you have available. Under-seat and other ultra-compact models produce some bass that adds a good extension to your music, but there’s no substitute for true air displacement like from larger subwoofers. The best sound generally comes from larger speakers like 8″, 10″, and 12″ speakers.

Tools I recommend for a successful installation

Example of a toolbox full of tools

I’d consider the following tools essential:

  1. Phillips & flat head screwdrivers
  2. Good & inexpensive wire cutting pliers
  3. Needle nose pliers
  4. Utility knife with a retractable razor blade
  5. Miniature flat head screwdriver or another similar tool to pry apart plastic trim panels and adjust the amplifier gain at the end

Ideally, you’ll have access to these as well, although I realize sometimes they can cost more than they should:

  1. Digital multimeter (test meter) for measuring voltages
  2. Cordless variable speed drill with clutch (absolutely FANTASTIC for speeding up work, drilling holes, and driving screws!)
  3. A good crimp tool & crimp connectors
  4. Wire stripper (not a need but greatly simplifies work effort)

Some of these can be bought at stores like Wal-Mart or Harbor Freight for a discount price. However, it’s hit-or-miss whether they carry all the items you need. Most can be bought for cheap on eBay or

I’ve been very happy with my digital multimeter from Harbor Freight. It was a great deal, and has lasted well! (Note: they also carry a cheap $3-5 budget version that will work also for installation troubleshooting).

Image showing example crimp tool and crimp connectorsA crimp tool (shown with crimp caps) is a great tool for a professional-quality installation to avoid having issues with wire connections later. I recommend blue butt connectors (right) as they’re a bit easier to use and fit 16-14 ga. wire but can also be used with smaller gauge wire if you fold it underneath itself before inserting it.

Installing subwoofers into a box

If you’re following my recommendation for buying a preloaded subwoofer box, then the work should be done for the subwoofer itself. If you buy an enclosure and subwoofers separately, you’ll need to install them securely.

Image of subwoofer installed in box and drywall screw

Install the subwoofer in the box.

I highly recommend using a cordless drill and drywall screws as they go quickly into the wood material of the box.

Most subwoofers use 8 screws. Don’t skimp on this! Subwoofers are heavy and have a lot of vibration when in use. It’s best to make sure they’re securely fastened.

If the cordless drill has a clutch set it to one of the first or lowest acceptable settings to make sure you don’t strip out the box material when fastening down the speaker.

Installing your amp & subwoofer

Here’s a general diagram to help you visualize the installation:  (Click to enlarge or click here to get the .pdf you can view or print)

How to install subwoofer and car amplifier infographic diagramInstalling an amplifier consists of several basic steps:

Route the positive wire cable to the car battery and hide it underneath the carpet and interior trim on the battery side of the vehicle.

In order to do so, you’ll need to pull up some of the interior plastic trim like rocker panel covers which usually snap off and snap back into place. Always be careful, and if necessary, carefully use a flat head screwdriver between gaps to help pry them off. Pull back the carpet to find room to hide your amp wire.

You can then find the edge of the carpet which is usually easy to pull back and tuck wire into.

Running wire to the car engine and battery

Honestly, getting the wire to the battery is usually the toughest part you’ll face. But don’t worry, there’s nearly always a gap, hole, plug you can remove, or a rubber wiring harness seal you make a hole in by pushing a screwdriver or similar tool through.

With a flashlight, look underneath the dashboard and try to find a plastic filler plug that can be pushed out (exposing a free hole you can use) or a rubber seal with a factory wiring harness that goes into the engine compartment.

If you need to do this, use a punch, pointed object, or even a very strong and long screwdriver to put a hole in the rubber seal. Then use the “coat hanger trick” to act as a wire snake for help pulling the wire through.

Image of positive amp wire pushed through firewall grommet

If possible, push a hole through a firewall wiring harness seal (“grommet”) and push the amp wire through that.

If by chance you find a plastic hole plug like this pop it out using a screwdriver and use it as a ready-made power cable hole. That makes things MUCH easier!

Image of engine compartment wiring harness rubber seal amp wire install

If you’re going through a factory wiring harness seal as pictured in the 1st pic, push it through until you can grab the wire and then from there pull it through the engine compartment. Then you’re past the hardest part!

The coat hanger trick

Image of straightened coat hanger

A useful trick is to use a coat hanger to make a “wire snake” to pull wire through tight and difficult areas, especially when going from the interior into the engine compartment.

With some pliers, you can straighten out a standard coat hanger to create a “wire snake” which is a tool used to pull wire through small spaces.

After doing so, you can wrap electrical tape around the power wire and attach it to the end.

Then push it through the car interior (if no easier alternative is available) and into the engine compartment, where you can then finally pull it through by hand and remove the power wire from it.

It’s best to bend the ends so that they’re rounded and won’t snap easily on obstacles in the way. For best results, make a small loop on the end where you want to attach your wire and wrap it well with electrical tape to smooth over sharp edges that may snag.

Running the wire the to back of the car

You may find it easier to remove the back seat and find a gap that will allow you to easily run the wire to the back. I usually find it best to first try to find a space where I can push my hand or fingers into the side gap of the rear seat (as the base of the top half of the rear seat) and find out if there’s a space available.

If not, I’ll try using the coat hanger trick, which almost always works.

Connect the positive wire to the fuse holder.

This is very straightforward. Trim about 1/2″ insulation from wire ends and assemble the fuse holder onto the exposed positive wire. Connect a crimp ring terminal and crimp using vice grip pliers (or other strong pliers) or a crimp tool.

Place the fuse holder near the battery with approx. 12″ or less of wire length, as that’s a general rule used to make sure there’s not enough wire to possibly be in a short-circuit without fuse protection which could cause a battery explosion or cause your vehicle to catch on fire.

Don’t think so? It happens! It doesn’t take very much for a pinched, unprotected wire to start melting the insulation and for a fire to start.

 Don’t install the fuse yet!  rimp ring and lug terminal examplesI highly recommend crimp ring terminals like those in the left picture and not those in the right picture (lug terminals).

It’s because lug terminals are far harder to crimp and may need soldering to make the best connection. 5/16″ ring terminals like those on the left are excellent and easier to use as well as being included in many good amp wiring kits. They’re also not very expensive.

If you can’t get the rubber sleeves to fit over your wire, don’t worry too much and leave them off if necessary.

Avoid lug terminals like those shown here. I’ve discovered that while they’re sold in some amp kits and are also sold in parts stores, they’re very difficult to use and need special high-force crimp tools or high-heat soldering tools.

They may very well keep you from getting your amplifier wiring installed, and I’d hate for that to happen

Connect the positive cable securely to the battery.

Use the ring terminal to fasten to a battery clamp bolt or stud. Use sandpaper or a wire brush to remove corrosion and expose clean metal if necessary.

Car amplifier positive wire and fuseholder installed at battery

For the best method, use a crimp ring terminal to attach the positive wire to the battery clamp on a stud or bolt. Be sure to remove the fuse before doing so, and install the fuse holder on the wire before connecting it to the battery. Hold in place by using zip ties to attach to nearby wiring, hoses, or brackets.

Connect the amplifier ground wire to bare metal near where the amplifier and subwoofer will be placed.

Use a crimp ring terminal and secure it to the car body (bare metal) with a factory screw or bolt. An alternative and faster solution is to use a cordless drill and self-tapping screw to drill into the metal and fasten the ring terminal at the same time.

Car amp grounded to factory ground location

If you can find a factory ground wire location in close range it’s an excellent ground wire connection point. Otherwise using a self-tapping screw and a cordless drill make the work very quick.

Connect the remote-on lead to the aftermarket car stereo and signal source

If the stereo in use is an aftermarket model a remote lead output wire should be available (blue or blue and white). Connect this to your remote on wire included with your kit.

If no aftermarket car stereo is installed, it will be slightly harder. In that case you have a few options:

  • Run the remote wire to a +12V wire switched on with the ignition or the accessory position of the ignition switch (this is the 1st choice)
  • Use a specialized adapter which senses music and when connected to a power supply can provide a remote lead signal

The 2nd option shouldn’t be necessary except in really tough situations.

Almost always you can find a +12V switched wire somewhere in the vehicle. It may take time, but using a good multimeter you can locate one and then connect similar to the speaker wiring connections shown below.

On most aftermarket car stereos a blue output wire is for switching an external amp on and off. It supplies +12V when the stereo is turned on. Connect to this if available. I normally use butt connectors (crimp connectors) for connecting wire securely.

Connecting the RCA cables – or connect speaker wiring if RCA jacks are not available

Remove your car stereo and get access to the rear wiring or rear of the stereo if it’s and aftermarket (non-factory) model. Connect to the RCA jacks if available in the following order of preference:

  1. Subwoofer output jacks (often marked SUB or SUBW)
  2. If 4 are available, use the REAR jacks
  3. If only 2 are available, then that’s fine as well

The left channel is marked with a white jack and red represents the right channel.

Plug your RCA cables to the rear of the aftermarket stereo, if available.

Connecting to speaker level inputs (if you have a factory system)

If no RCA jacks are available or you have a factory car stereo, you’ll need to tap off of speaker wiring to get an audio signal source. This may be easier to do while you’re connecting the remote wire at the stereo. If there are rear speakers in the vehicle, that’s another option too as speakers in a trunk may have fairly easy access to speaker wiring.

You need to find wiring information for your vehicle and check at sites like for wiring charts.

Image showing car speaker wiring tap how to

At each pair of speaker wires or near the speaker wire connector, strip off about 1/2″ of insulation and tap off it. To do so, either wrap wire or cut the factory wire and connect to it using crimp connectors while attaching a small gauge wire when doing so.

Crimp connectors (see the tool list above) are reliable and make good electrical contact. I recommend you use those if possible.

Image of car stereo wires crimped

Route wiring to the amp location

After connecting the power wire, remote wire, and signal wire move it down to the same side of the car (as needed) and when the wire comes together use zip ties (also called “wire ties”) to neatly hold it all together. Use wire cutters to cut off the extra remaining zip tie length.

Wire bundled with zip ties exampleBundle your power and cable wires together neatly like this. To save money you can space out zip ties roughly 12″ or so apart to avoid using too many. The ties hold wiring in place, make it more manageable, and help keep things from moving around over time.

Mounting the amplifier

Example of 2 custom car amp installations

Two amplifier mounting ideas that work for nearly all installations. Don’t sweat it! One of these should work. However, the board mounting idea looks much better and means you can mount your amp out of the way in many cases.

For most people there are 2 great and simple ways to mount your amp reliably:

  1. On the subwoofer box
  2. Make an amp mounting board and attach it to the car securely

I prefer #2, as it’s a better looking and more professional method. It’s slightly more work than #1, but looks wonderful and it also avoids subjecting the amplifier to extreme vibration like when mounted to a subwoofer box.

For option #2 you can buy a nice speaker box carpet or a dark fabric from Joann or some other fabric/crafts store and cover the board using an adhesive spray and/or a stapler, then mount it using brackets or car stereo straps.

Black fabric is available in a variety of fabric types (I’ve used black felt or velvet-like materials often for custom installations).

A big advantage of using a custom-cut amp rack (amplifier board) is that it allows installation in locations otherwise not possible.

Just cut a section of board (bought from Lowe’s or Home Depot for example) slightly larger than the amplifier, mount it using brackets or straps, and that’s it.

As long as you have room and the parts for mounting the board, it’s relatively easy! You can find some great ones I use here.

Car stereo installation pan head screw and metal strap examplesUse pan-head screws (left) and not self-tapping screws when you’re mounting items to wood or wood-like materials. Car stereo installation straps (right) are fantastic for custom mounting amplifiers, amplifier boards, and subwoofer boxes to a car.

Connect all wiring to the amp and the subwoofer

image of car amplifier having wire connected

This is the easy part! And you’re in the “home stretch” – there’s not much left at this point. If all goes well, you’ll have awesome sound really soon.

With the power turned off and power wire fuse removed, connect the power wire, ground wire, and remote wire to the matching terminals. Normally the positive and negative terminals are larger than the rest.

Make sure you have a good, tight connection without any stray wires sticking out in a way that may lead to a short-circuit.

(Click to enlarge & zoom)

Image with diagram of how to bridge an amplifier

Connect the larger speaker wire you bought to the speaker terminals of the amp. If you’re using a bridgeable amplifier connect the wires to the amp in a similar fashion as shown here. If using RCA inputs, connect to the input pair for the speaker outputs you connected to.

If using speaker level inputs from a factory system connect them now. They should be labeled and/or color-coded to make it more clear.

Power on the system and check for problems

Install the power fuse and turn on the ignition and your stereo. You should hear sound and the amplifier power light should indicate that it’s on. If not, check the following items for problems.

Quick Tip
Use a test meter when possible for troubleshooting amplifier problems. Test lights don’t give you enough information. Many amplifiers can have a good ground and +12V battery connection but won’t turn on if the remote lead is below a certain voltage, for example, so it’s important to be able to find out what’s going on.

If you don’t have sound or power, it’s more than likely due to one of these common causes:

  • Poor car ground wire (measure continuity between the amp negative terminal and a metal part of the car)
  • Fuseholder problem or bad fuse
  • Remote wire voltage is too low or +12V isn’t being supplied at all

Generally, there are only a few reasons why an amp can’t turn on and produce sound, so it’s normally one of a few basic problems like I’ve listed here causing the problem.

Setting the gain and bass adjustments

The problem with having sound adjustments on both the stereo and the amplifier is that settings can be all over the place and one can affect how the other produces sound to your subwoofer.

I recommend doing the following:

  1. Turn off all bass boost or equalizer (EQ) functions on the stereo or set to mid-level or zero.
  2. Turn off any bass boost controls on the amp or turn to the minimum level
  3. Set the amp gain to its minimum

Alpine MRV-F300 4 channel amp end view

Most well-designed amps like the popular Alpine MRV-F300 feature flexible crossover controls you should use. With them, you can get clean, low-distortion music power at high volume. Surprisingly very few people use these features to their potential!

Play some music you’re very familiar with and that you know should have good bass sound at a moderate level. Then with a small screwdriver or screwdriver bit that fits adjust the gain until bass performance is at the level you enjoy.

Don’t forget that when an SUV hatch or car trunk is closed the sound will be changed somewhat as opposed to when the door, trunk, and/or rear hatch are closed.

In case the stereo has insufficient bass or your system still doesn’t sound quite right, try using the bass boost on your amp if available.

A bass boost typically works boosting bass response around a fixed or adjustable frequency near 50Hz for example. These can sometimes add some extra “thump” and bass extension to your audio system.


I hope my guide has provided a lot of helpful information. That’s what I’d love to do because I want everyone to know how great it feels to install your own car subwoofer and amplifier.

One important tip: for factory-installed “premium” audio systems like Bose, JBL, and Harmon Kardon it can be difficult as those systems are far more complex.

Generally speaking, you should still be able to add a subwoofer by tapping off of a pair of factory speaker leads in most cases.

If you run into problems or don’t feel up to the task consider getting an estimate speaking with a reputable car stereo shop. If they say your vehicle will need parts and add-ons not listed here be sure to ask why.

Add-ons are a very big moneymaker for car audio stores.

Whatever you do, don’t feel intimidated. Follow my advice here to be better prepared and take your installation one step at a time.

Nearly everyone can install their own subwoofer in their car and enjoy fantastic bass!

Recommended items

As I mentioned in my guide, I generally recommend using a multi-channel amplifier. Here’s a great list I’ve put together of some of the best affordable and well-performing models.

Here's a very good and complete amplifier wiring kit to make the job easier (I’ve found some of the best values at Amazon).

One of the best car stereos I’ve found is this Alpine CDE-HD149BT Advanced Bluetooth CD Receiver

Print outs

  1. Basic how-to infographic (.pdf file)
  2. Car amp installation diagram
  3. Basic speaker wiring diagram for woofers

About the author

Marty is an experienced electrical, electronics, and embedded firmware design engineer passionate about audio and DIY. He worked professionally as an MECP-certified mobile installer for years before moving into the engineering field. Read more »

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