Installing Subwoofers in a Car





Introduction: Installing Subwoofers in a Car

In this instructable, I will show you the whole process of installing an amplified subwoofer into a car. After you have your subwoofer system set up, you will hear much better sound from your stereo.

This process will work with most stock stereos, and all aftermarket stereos. It can be modified to work with all stock stereos, but you may need a few more parts. I will show you how to do this with an aftermarket head unit (stereo).

When you look at the pictures, realize that I am using an amplifier that is too small for the subwoofer. It is for demonstration purposes and it does not sound as good as it should. In other words, my car needs a bigger amplifier to support the subwoofer.

Step 1: Parts

So what will we need to do this?

-Subwoofer box
-Subwoofer speaker (see next step)
-Amplifier (see next step)
-Wiring kit (or each of the following)
-10 Gauge or thicker, 20 foot insulated wire (for power)
-10 Gauge or thicker, 3 foot insulated wire (for ground)
-18 or 16 Gauge, 15 foot wire
-RCA cables, 15 feet or longer (you need 2 or one with both red and white)
-In-line fuse, 50 amps or higher
-Some speaker wire
-4 small wood screws
-Basic tools

For the power and ground wires, you will need thicker wires depending on how powerful the amplifier is. REALLY powerful amps could need as much as a 0 gauge wire. But I doubt any of you guys will be using an amp that big.

Walmart sells amplifier kits (as do some other stores). The kits tell you how many watts they can handle.

Step 2: Choosing an Amp and Speaker

This can be a tricky step. You want to choose a speaker and amp that put out the most power, without blowing each other.

What you want is the RMS of both the subwoofer speaker and the amplifier to be as close as possible. The RMS is the amount of power a speaker can continuously have sent to it without going bad. The RMS is also the amount of power the amplifier can continuously put out without over heating.

When looking at speakers and amplifiers, do not look at the peak power. A speaker or amp can only be run on the peak power for about a minute before it goes bad or overheats. You want to be running your subwoofers on its RMS rating rather than the peak rating.

For best sound, keep the impedance (Ohms) the same too.

Lets take the Kenwood KFC-W3011 for example. Its ratings are:
-400w RMS
-1200w Peak
-4 Ohm Impedance

A good amp for this speaker (assuming this is the only speaker attached to the amp) might be the Rockford P400-2. This amp has the following ratings when it is in "bridged mode".
-400w RMS
-4 Ohm Impedance

Choosing a size for a speaker is also important. Smaller speakers like the 8 and 10 inch ones, are very quick to respond and punch better than bigger ones, but are not very loud. Bigger ones like 15+ inch ones, are very loud compared to smaller ones at the same wattage, but have slow response, and make the sound more mushy. The bigger ones also handle lower frequencies better too. 12 inch speakers are a good compromise for a basic system.

Make sure you buy a subwoofer box that has a hole the same size as your speaker.

Step 3: Run Wires - the Most Annoying Part

We will start with wiring the power from the battery. It is important to get the power from the battery and not the fuse box. Power from the fuse box often is "unclean" and you may hear your engine noise amplified through your speakers. You could also easily blow a fuse by using the little ones the fuse box has.

Start by finding an opening in the car's firewall. This is the metal wall under the hood of the car, closest to the windshield. The other side of the firewall should be the inside of the car. I chose a hole that was behind my glove box and was fairly easy to get to from the engine compartment.

Run the majority of the power cable through the hole in the firewall, making sure to leave enough wire to get to the battery.

Strip the insulation off of the wire at the end where the battery is. Wire the in-line fuse to this end (if it is not part of the wire already). You want the fuse as close to the battery as possible. Do not connect the wire to the battery yet. Make sure you tape the place where you wired the fuse to the wire, so you don't get a short.

Run the remaining wire under the cars carpeting or through a wire channel, if there is one. You want to get this wire to the trunk of the car.

While you have the carpeting loose, run the 16 - 18 gauge wire and the RCA cables from the trunk to as close to the back of the stereo head unit as possible, leave a little slack at both ends.

Step 4: Wiring the Audio

You now need to take the stereo head unit out. I can't tell you how to do this, because almost every car manufacturer does it different. It usually requires you either take off the front of the center console, or you use a tool to slide the stereo out of special clips.

After you have the stereo out, look at the back of it. There should be 2 RCA connections. Run the RCA cables through the back of the center console and plug them into the 2 connections on the back of the stereo.

If your stereo does not have these connections, you will have to splice the wires into the rear speaker wires. Better yet, go out and by a new stereo that has RCA. They aren't very expensive any more.

Leave the stereo out for the next step.

Step 5: Wiring the Remote

You will need to run the 16 - 18 gauge wire through the back of the center console too. This wire tells the amp that the stereo has turned on, and that the amp should too.

If you look at all the wires coming out of the back of the head unit, there should be 1 or 2 blue ones. These are called the remote wires. If your wires are labeled they may be labeled as:
-Power Antenna
-Pwr. Ant.
or something similar to one of those.

If there are 2 wires, there should be one labeled Amp. If there is just one blue wire, you can use that. If you have a power antenna, you will have to splice into the blue wire for use with the amp too. What you need to do is connect the 16 - 18 gauge wire to the correct blue wire. When the stereo comes on, so will the amp.

If it is a stock stereo on a car without a power antenna and no blue wire, then run the 16 - 18 gauge wire to the fuse box, and connect it to a fuse that turns on when the accessories are on. Your amp will always be on when your car is on, but it shouldn't make noise, so its OK. If it does make noise (like from the engine), add a switch so you can turn it on or off.

Step 6: Put the Speaker in the Box

This is pretty self explanatory, but for those who don't know:

Put the speaker in the box, making sure the flimsy thin gasket thing is on it.
If the box has its own connectors on the outside, make sure they are wired to the speaker inside.
Screw the speaker into the box, using the holes on the outside rim of the speaker.

Set the subwoofer in the trunk of the car.

Step 7: Wiring Up the Amp

OK now we have most of the wires in place, we can wire up the amp.

Connect the power cable from the battery into the spot on the amp that has one of the following markings (do not connect it to the speaker positive):

Connect the 16 to 18 gauge wire into the spot that says:

Connect the 3 foot, 10 gauge wire to the one marked (do not connect it to the speaker negative):

Connect the other end of the ground wire to a nearby bolt that connects to the body of the car.

Connect the speaker wire to the + and - marked for speakers on the amp. There may be 2 channels. If there are 2 channels and you can bridge your amp, do it. I won't explain bridging but its easy and you can Google it.

Connect the other end of the speaker wire to the + and - on the speaker box. Try to make sure that the + from the amp is connected to the + on the speaker, and the same with the -.

Step 8: Adding Power

The final step is to go and connect the power cable to the battery. I just shove my wire between the battery clip and the post on the battery.

Make sure a large fuse is in the fuse holder.

Step 9: Play Loud Music

Your done!!!

Test it all out and make sure it works!!!!

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Please be positive and constructive.



first time I am installing a subwoofer in my car and I need to connect outline converter in my car radio. I bought 2 channel outline converter from e bay and I need to tap into factory cable speakers but not sure with speakers I should tap. front or back? My front speakers have no Bass at all and rare speakers are batter and with some Bass. can someone please give me advice about which speaker cable I should tap to connect lineout converter please?


Hi Guys,

Can any of you help me. I have had my sub for a few years and recently I had a few things in my boot, as i went round a corner something fell and it pulled (ripped) one of my cables off my speaker (picture below). Is this something i can easily fix? and if so how?



i think soldering it back and wrapping a ton of electrical tape should do it

After installing my amp and subwoofer into my 2000 jeep wrangler, my rear speakers (on the sound bar) are no longer working. Any ideas/sugestions?

Buy a better car :D


I Like that and pmsl .

Hooking up cadillac sts 05 amp and 10" sub would love some info on what wires to buy and where, thanks

Check this out - it's a bundle, has everything you should need to do the job.

hi guys

i have 2dvc comp 4d sub targa

i need to build a box for it pls help wat is the right size of the box

and im using star sound class x amp

selecting speakers for amplifier. This article has a huge mistake. One should never match amplifier power with speaker power. Here is why. Amplifier power measuremnt is watt rms. Rms stands for square root of the average of square. The important thing here is AVERAGE. The speaker power is expressed as the maximum input. In electronic we call this the crete to crete value.

If you pick a speaker with maximum rated input of 100 Watt to connect it to an amplifier with average output of 100 Watt, then never crank the amplifier to max or you'll end up damaging the speakers. The good pratice is to pick a speaker rated for 170% of the amplifier power. A 100 watt rms output should never be inputed in a speaker with less thant 170 watt mximum input.

If you follow this guideline, you won't blow up you speakers and improve sound output quality !