Modern car audio systems provide drivers and passengers with high-quality entertainment at relatively affordable prices. But even many high-end sound systems mostly focus on providing good midrange and treble but do not properly reproduce sound. Part of the problem is that car stereos generally have a small and low-power amp pumping out the sound. The lack of low end makes many car owners look for information on how to connect a subwoofer to a car stereo without an amp.
Without the low end produced by a subwoofer, you cannot hear the true sounds as recorded and intended to be heard by the recording artists. The problem is, many subwoofers require significantly more energy than the typical car stereo internal amplifier can produce. But not all of them.
Can I Connect a Subwoofer to a Car Stereo Without an Amp?
Yes, there are ways to connect a subwoofer to a car stereo without an amp. The simplest is to obtain a subwoofer that relies on a passive system to power it up. That means the juice already going through the audio system will produce the power needed for the subwoofer with a passive system. The result might not be an overwhelming bass response of many subwoofers with active systems, but it should be plenty to fill your vehicle with great lows.
Installing a passive subwoofer is as simple as installing any other speaker. You just connect the leads on the subwoofer to the corresponding location on the car stereo. Once you have the subwoofer connected properly and the cover in place, you can enjoy an improved audio experience in your vehicle with a passive subwoofer.
How do I connect a Subwoofer to a Car Stereo Without an Amp?
A more significant issue is when you want to use an active subwoofer that kicks out plenty of low-end sound to your car’s audio system. Fortunately, most current car audio systems are equipped with several speakers. This is great, because you will need to render at least two and possibly more of them useless in order to take the power that they have used and send it to the subwoofer.
The subwoofer will become a kind of parasite when you bridge the output connections for either two or four speakers located in the back of your vehicle. You can take that power and send it to the subwoofer and use the power intended for two or more speakers to power the single subwoofer.
The stock car stereo likely will have one of two types of amps. One is an internal amp that is integrated within the audio unit’s housing. Such amps generally are very weak and are included with less-than-premium audio systems.
The other type of amp is an external factory amp that likely is located under the hood near the firewall or possibly under the dash. Some might have the amp located in the trunk or rear of the vehicle. Regardless of where the amp is located, a subwoofer that does not have an amp could use the factory system to provide the required juice to improve your listening experience.
Why Use the Back Speakers?
With some audio systems offering a dozen or more speakers to provide full sound in SUVs, minivans and other vehicles, the rear speakers mostly provide filler sound for the regular driver and his or her regular passengers. Many people drive solo more often than they travel with passengers, so the rear speakers do not matter as much as the front and middle speakers for the driver and front passenger.
The back also likely is where the subwoofer will be positioned, anyway. You might have a creative idea for a front subwoofer or another unusual mount, but most people find the rear is the best location and likely in the trunk or very back of an SUV, van or car. So the rear speakers often wind up being the default speakers to disable because they are the least-used speakers and conveniently located closest to where the subwoofer often is mounted.
What if My Car has a Factory Amp?
If your vehicle has an external factory amp, you are in luck. You can purchase a bypass harness that enables you to jump to the power output intended for the rear speakers and send that power to the subwoofer. You need to locate the factory amp on your vehicle and obtain the correct bypass harness from an automotive parts store or possibly a car stereo specialist.
With the correct bypass harness, you can just unplug the stock harness and plug the bypass harness that includes the power for the subwoofer. You get to keep your full stock stereo system in use while adding the subwoofer to the sound mix for greatly improved listening pleasure.
What if My Car has a Weak Amp?
If your car does not have an external factory amp that you can jump with a bypass harness, you can take power from a couple of speakers. The same tools used to install a car stereo system will work fine with installing a subwoofer and jumping power from a couple of speakers. You will need a flathead screwdriver and possibly a Philips-head screwdriver to remove the speaker cover and detach the donor speakers to access their outputs
But you also will need a wire capable of carrying a good amount of power for extended periods if you go on long road trips fairly often. If you use wire that is too thin and incapable of carrying the power, the insulator could melt and a short could occur. That might damage the entire system and leave you with no sound system at all.
A soldering iron would be preferable to crimping on lead to the wire that you will use to connect the speaker outputs to the amp inputs on the subwoofer. The output from each speaker combines into a single unit that you can affix with either solder or crimping a metal piece to the end and screwing the connection into the subwoofer at the proper location to deliver plenty of juice.