How to connect a subwoofer to a car stereo without an amp

Today, carsaudio presents to you the most simplified and well-elaborated informative guide on how to connect a subwoofer to a car stereo without a car audio amplifier. This guide will be of very great importance to both car audio installation gurus as well as newbies in the industry.

What is a car audio amplifier?

A car audio amplifier is an electronic device designed and manufactured to boost very small electric audio signals from the car stereo head unit to a higher voltage. The high voltage translates to the power output a car audio amplifier can generate to power up car speakers and subwoofers. Therefore, in short, it increases the power of low-level frequency audio files to add more robustness to your car audio system by boosting the highs, mids and lows output.

External vs internal car audio amplifiers

With an external car audio amplifier once connected to the car stereo speakers, you will experience more audio clarity and volume which would not have been possible to reproduce by the use of the inbuilt amplifier found in a car stereo head unit. You will find that inbuilt car audio amplifiers are underpowered with about 15W to 18W of RMS power output. This is very low power to use with especially aftermarket speakers and subwoofers. You will also experience a lot of audio distortion, especially at high volumes of audio play.

An external car audio amplifier is used to solve this audio distortion menace by supplying more power to the car stereo speakers and subwoofer. This greatly improves the reproduction fidelity of the music allowing you to have one of the best experiences while driving. For powerful bass notes to be reproduced, subwoofers require to be supplied with more power which will require you to install a car audio amplifier because of the underpowered head unit inbuilt amplifier.

Also, aftermarket speakers which are used to replace factory car speakers require more power supply for maximum performance without any sort of audio distortion. Most aftermarket speakers are rated 4-ohm or 2-ohm hence more power is demanded in order to have the best audio performance.

An external amp provides higher sound quality as it can offer lower noise and distortion due to more advanced electronics included for that purpose. Car audio amplifiers which are inbuilt often use a more basic design architecture where cheaper components that limit what you can hear are used, unlike external car audio amplifiers where they have more advanced electronics which allow less to no sound distortion even when playing audio files even at maximum volume.

Our focus

In this article, we will focus on internal car audio amplifiers. An internal power supply is supplied by the car battery to generate a higher output voltage hence more power than is otherwise possible to produce from a 12-volt power source. Due to the large amps that are drawn by the car stereo system, car audio engineers needed to install thick gauge power wires and ground wire connections to the vehicle battery and the car metal chassis directly in most cases. A car stereo system sends an audio signal via RCA cables or other connections where the boosted electrical signal is delivered to speaker terminals for use.

Therefore, this article is meant for those car owners who have a car stereo upgrade but they are not in a position to buy or afford an eternal car audio amplifier but still want to get the best out of their audio system whenever they listen to music. We understand the importance of music while driving on a long drip because it helps relieve driving pressure and also at the same time keeps you lively hence reducing the incidence of dozing off while driving.

The desire to blast your favourite song aloud and get immersed in it with the pomp, excitement and fun that comes with it is undeniable. This makes car audio amplifiers very important in-car stereo systems where they are internal or external. Subwoofers are the only car stereo audio components that will require more power supply but the lack of an external car audio amplifier does not make your aftermarket subwoofer worthless. It will still work but the drawback is that it will not be at its best performance as desired to be outputted by the manufacturer during its design.

So, if you want to invest in a subwoofer and do not have an external car audio amplifier to power it, that is not the end of the road. As you read along, you will find out how you can enhance the performance and quality of your subwoofer without an external car audio amplifier, thereby making it compatible with your car stereo system.

A basic guide for an internal car audio amplifier connection

An internal car audio amplifier can be used to hook up a subwoofer without connecting an external amplifier to power it up. This can be achieved by disconnecting the rear car speakers whereby their channel outputs are used to bridge for one large power output that can be used to power a non-powered subwoofer.

Please note that you will not be in a position to use your rear speakers at the same time while using the subwoofer because the internal car audio amplifier has no capacity to power up the whole system. If they are all connected to an internal audio amplifier, the rear speakers will be low-powered where they will not deliver enough RMS power they are designed to output because the subwoofer will be using up most of the power channelled to the rear.

Wiring a subwoofer to a car stereo system is straightforward hence you should just relax and feel less bothered. This is because the subwoofer is connected to the power source by the combined rear speakers’ channel. This is a very easy process where we will discuss it broadly in the next few subtopics.

Performance-wise, the accurate, loud and deep bass output will not be fully achieved as compared to an external car audio amplifier connection. This is due to the MOSFET transistors present in most car stereo head units being less than 30W. A trick can be applied to double that power output by bridging the rear audio channels and making sure that you intend to power only one subwoofer unit.

Mid-range audio frequencies will be heard coming from your subwoofer due to the lack of a Low-Pass Filter (LPF) which allows only passage of low-range frequencies by cancelling out the high and mid audio frequencies. A quick fix to this problem would be achieved by turning down the treble and increasing the bass settings on your car stereo equaliser.

Types of car stereo-subwoofer connections

There are two major types of car audio amplifier connections to a car stereo system with a subwoofer. This depends on whether the subwoofer is a passive subwoofer or a powered subwoofer.

The passive subwoofer does not have an internal amplifier installed in its cabinet hence they are required to connect to an external car audio amplifier. For powered subwoofers, they come equipped with an inbuilt amplifier which is then connected to the car stereo. This saves on time and money because you will not have to buy an external amplifier and the time required for installation is minimal.

(i) Passive subwoofer connection

A passive subwoofer, as we just explained earlier is a subwoofer without an inbuilt amplifier, where installation connections are made just like any other car speaker. A point worth noting is to ensure that you disconnect the ground wire from the car battery before proceeding with any installations.

Rear car speakers have wires that run from the head unit to the rear of the car. These are the wires that you are going to use to connect your passive subwoofer to your car stereo system. These wires, while ensuring the polarity is well matched, connect the subwoofer wires to these car speaker wires. That’s it! The only problem is that you will have to forget about deep bass audio production from your passive subwoofer because you are using a factory car audio amplifier which is inbuilt into the head unit.

If there are no existing car speaker wires at the rear of your car, you will have to drive wires from the head unit harness from the car dashboard, the same way as you would do for the car speakers. the same procedure should be followed just by doing an installation where a car speaker wires already existed.

(ii) Powered subwoofer connection

The powered subwoofer connection to the car stereo system without a car audio amplifier is just the same as in passive subwoofer installation.  This is a straightforward process which involves easy steps to achieve a perfect connection. A powered subwoofer comes fully equipped with the necessary installation wires and an inbuilt amplifier too hence no need for an external car audio amplifier connection.

Let’s start! Disconnect the ground wire from the battery and remember to reconnect them after the installation. All wires should be concealed by running them inside the carpet. This will maintain the car’s aesthetics while providing damage protection to the wires. Run the power cable from the battery to the subwoofer installation point.

The next step is gaining access to the head unit from the dashboard and accessing the wiring harnesses and outlets. Run the RCA signal wires from the exposed car stereo head unit to the subwoofer which should also be concealed beneath the carpet. A point to note is that the RCA cables and power cables should not be run together, hence they should pass on separate sides.

Ensure that you ground the passive subwoofer to an unpainted part of the car using a grounding wire. Some active subwoofers come equipped with a control wire which needs to be run close to the point of usage, either closer to the dashboard or the steering wheel and not cause driving interruptions.

With all connections done, place a removed earlier ground battery wire on the battery negative terminal and screw it back, ensuring a tight and secure connection.

The procedure of connecting a subwoofer with no amplifier to a car stereo

The requirements

(i) Tools

Before you start the subwoofer connection process to your car stereo system, the following are the required tools to get the job done. Ensure these tools are complete, rightly arranged, and placed within your easy reach. They include:

• Wire warm tool
• Spanner
• Trim panel tools
• Wirecutter/stripper
• Screwdriver
• Pliers
• Electric tester
• Hammer
• Flashlight

(ii) Time

When it comes to connecting a subwoofer to a car stereo without an amp, it requires time but not as much as when you are installing a car audio amplifier. The installation process is elementary and hence not complicated. It requires a patient soul to have car audio devices installed to be fully functional.

Installation time varies according to the skills of the installer. If the car audio installer is experienced it takes less time because of the elimination of the trial-and-error procedures. On average the installation process will require around one to two hours to fully connect a subwoofer to a car stereo including all the final touches such as wiring concealments.

(iii) Cost

The cost factor is a key consideration in any car audio installation. It all depends on your tastes and preference and the current audio component you got. If you are buying all components such as an aftermarket subwoofer, budget more cash. If you are using a hired hand to perform the installation, then you will also cater for their job fees.

On average a top-quality mid-sized subwoofer costs around $200 excluding the subwoofer box enclosure. Small-sized or compact designs are offered at lesser prices, although they may not produce the same sound quality as larger ones.

Fee charges for hiring a professional car audio installer vary depending on the region, country or the complexity of the audio installation procedure and at times the car type, but on average it will cost you around $100 to $300. Therefore, it is up to you to work with your budget to avoid overspending or breaking into the bank.

The procedure

(i) Disconnect the car battery

The car battery is the source of electrical power with most cars having 12V output. The battery powers the car even when it is in a stationary position. It provided DC electrical power which powers electrical components of the car such as the car stereo system.

The battery’s disconnection is the first step. Carefully unplug the negative terminal wire connected to the battery because it also acts as the grounding wire. This will prevent electrical shortages in the car’s electrical system. Ensure the plug is placed away to avoid reconnection. Performing car subwoofer installations with the power not disconnected will lead to draining the battery because the subwoofer consumes a lot of power which is something we would like to prevent.

(ii) Disconnect the infotainment system

Once the battery is disconnected, now it is time to disconnect the infotainment system. If you do not have an infotainment system, skip this step and go to the next step. This unit should be fully disconnected. Access should be via the removal of the dashboard panel using the panel removal tool kit.

Ensure you exercise care to avoid breaking or damaging the panels. The purpose of detaching the infotainment system is to eliminate any chance of electrical shock as you detach the car stereo speakers or when you are accessing the rear section of the infotainment system.

(iii) Detach the fuse

Detach the car fuse from the fuse compartment box mostly located at the car’s boot. Detaching the fuse allows you to connect the subwoofer to the main power supply.

(iv) Disconnect the car stereo

The fourth step in our procedure is disconnecting the car stereo head unit from the dashboard. The car stereo head unit is normally docked in the mounting docks. Unclip the clips and unscrew any screws used in holding the head unit into position. Slide-out the head unit carefully in order to access the rear end of the head unit. At the rear end, you gain access to connecting components such as the RCA cables and grounding wire.

Make sure that you do not interfere with cables not required for the installation. Identify the subwoofer or rear speaker outlet RCA cables as they are going to be used when connecting the subwoofer to the car stereo without the need of a car audio amplifier. Identifying and locating the car stereo system wiring is an essential aspect of this subwoofer installation process.

(v) Stereo adapter attachment

A stereo adapter is a necessary car audio tool which needs to be included during a car subwoofer installation. A stereo adapter, as you might be wondering is used to provide power where it regulates the power from the battery to the required power level designed for the subwoofer.

Ensure that the stereo adapter and the stereo cable are rightly combined, thereby providing the ultimate power source needed to operate your subwoofer through a particular cable. This will prevent any malfunctions during the operation of the subwoofer. Once you have completely wired the subwoofer to the stereo adapter, recheck the connections to make sure that they are well installed. Afterwards, extend the connecting cable to the installation position of your new subwoofer.

Ensure firm connections of the stereo adapter and subwoofer wiring harnesses. You will be now fully prepared to use your subwoofer with no need for an external car audio amplifier.

(vi) Mounting the car subwoofer into position

There are various places that you can use to mount the subwoofer in your car. It all depends on the type of subwoofer. If it is an under-seat subwoofer, place it under the seat or in a shallow mount subwoofer installation point in your car. For the subwoofers that require you to have a subwoofer box ensure that the subwoofer is correctly installed. for these types of installation, space is required due to the size of the subwoofer box spacious installation locations are the car boot.

For best sound performance, your subwoofer must be rightly placed in a location where it is convenient and ideal to support appropriate integration. Asides from improving the audio bass quality, the installation location of the subwoofer should be easily accessible, especially during the installation process such as when adding accessories such as crossover integration between the head unit and subwoofer.

(vii) Reinsert detached components

Car audio installations can be messy due to the disassembly involved during the installation process. Many wires get exposed as well as car interior components such as dashboard and body panels get disassembled in order to expose the wiring and other car audio components. Therefore, all detached car accessories should be correctly installed to their original positions and all mess cleared. Some of the things that you should not forget about are; reconnecting back the grounding wire, the fuse and the car battery connections. Also, ensure all cable harnesses are correctly installed.

(viii) Final check

The general assumption for this stage is that all the necessary connections have been made properly. This makes it the easiest step of the process. You can refer to photographs to ensure everything was correctly installed to the original location or you can use the car’s audio installation diagrams provided in the manuals.

The main car audio component we will be installing today is a car audio subwoofer. Therefore, it should be the main component of interest hence testing its operation whether it is to your expectations and preferences. Test it by playing one of your favourite music files and pay great attention to the bass audio produced. If the bass audio is deep and natural, free from any distortion then you have done a nice job. If there is distortion, you can use the head unit equaliser to fine-tune the audio reproduction.

Ensure that all the cables can be concealed and covered beneath the door panels or car carpeting to ensure safety and any form of physical damage to them. This will make the car audio system last longer with zero maintenance procedures which are expensive.

After completing the above car subwoofer with no amp installation process, next, we are going to highlight some other connection techniques that you can adopt. The procedure we just described is standard for most car audio installation setups.

Car stereo and subwoofer connection points

Some necessary connection points that should be readily available on your car stereo system head unit and subwoofer include:

(i) Using the RCA cables

RCA cables are used in connecting car stereo head units to audio components where they transfer audio/video signals. They are used in car stereos that have left and right (L & R) stereo connector ports. During your car subwoofer installation, connect these cables as they are colour coded by extending them and plugging them correctly.

Once correctly installed, your subwoofer will be ready to kick in and produce that deep bass audio that you have been yearning to listen to.  RCA cables are used with car stereo systems that do not have the Low-frequency Effect (LFE) cables but have the L & R stereo connectors.

(ii) Using the Low-Frequency Effect (LFE) cable

The Low-frequency Effect (LFE) ports allow easy connection of the car stereo and subwoofer. They come labelled as “Sub-Out” or “Subwoofer” on your subwoofer connectors present on the enclosure box. This is easier to use than RCA cables because the LFE cable port is labelled as an output on the car stereo head unit and as input on the subwoofer unit. Once you have identified the connection points, make the connections and ensure that test before extending the cables. Once fully connected, that’s it! You can now enjoy your music with the additional bass audio notes well enhanced by the subwoofer.

FAQs and general information

(i) How can I get bass without a car audio amplifier?

The primary function of a subwoofer in your car’s stereo system set up to reproduce and enhance the low-frequency range audio notes while ensuring they are crisp and clear

Just like every music or sound enthusiast, the goal is to get the best response and performance from your subwoofer. By tweaking your subwoofer installation, you can get much bass out of it without installing a car audio amplifier to your existing system. This is cost-effective as well as fulfilling. The adjustments are basically simple and easy to implement with minimal technical know-how required and specialised tools. Some of the steps that you can incorporate include:

•  Accurate positioning and installation of your car subwoofer are very crucial when it comes to getting the best bass output. First, ensure that your subwoofer is placed in the rear corner of your car. Subwoofers are ideally installed at the rear due to their space requirement. Rear installations will guarantee an extra 6 decibels of bass increase hence eliminating the need for extra amplification.
• Trial and error techniques are also applicable to in-car audio installation procedures. Try and place the subwoofer in various locations in your vehicle until you find a spot where you hear the exceptional bass sounds of desirable quality. Do not position a car subwoofer on parallel surfaces or at an equal distance between two car walls. Placing it asymmetrically is a great idea. This improves the overall bass sound quality.
• Lastly, ensure the perfect and accurate connection of the subwoofer to the car stereo components. Ensure that the subwoofer’s crossover controls are appropriately adjusted, cables well connected, power cable polarities well checked and also the subwoofer is well fixed to prevent movement while driving, for example on rough roads.

When you follow the above tips and put them into practice you will get a more impressive deep bass audio from your subwoofer at no extra cost.

(ii) Which subwoofer type can I connect to a car stereo without a car audio amplifier?

The best type of subwoofer that will work without an external car audio amplifier is an active subwoofer. Active subwoofers come integrated with their own inbuilt amplifiers and their input power demand is much less than those of the huge passive subwoofers. They produce decent deep bass which is satisfying to most casual music listeners. They are cost-effective and easy to install. Some common active subwoofers include:

• Under-seat subwoofers. They are installed under car seats or in cars with space limitations such as trucks and sports cars with a centrally positioned engine.
• Bass tubes. The subwoofer is installed in a tube enclosure hence its name “bass tube”. They are easy to install and subwoofer drive unit size ranges from 6 inches to 12 inches. They occupy less space and are easy to install as well as produce great quality bass audio.
• Spare wheel subwoofers. You can utilise the spare wheel space in your car’s boot by installing the subwoofer in the spare wheel’s rim space. This saves on the car boot space by a big percentage as well as enriches the bass audio of your music. Some of these subwoofers have better performance than under-seat subwoofers.

Final verdict

This article has covered broadly the various installation steps, car audio components and measures that should be taken when connecting a subwoofer to a car stereo without an amplifier. A subwoofer installation is a necessary car audio component worth considering to have installed on your car stereo system.

A subwoofer will provide and enhance the audio files being played from your car stereo system by enriching them with deep bass audio. This allows you and your car occupants to enjoy music for an exciting, thrilling and fun-filled driving moment no matter how long it takes. May it be a casual drive to the shopping mall, gym, restaurant or a long pre-planned road trip, it will suit your needs.

Connecting a car subwoofer to a car stereo without an amplifier is cost-effective due to the lack of other car audio components such as crossovers and an external car audio amplifier. Bass quality will obviously not match that of a subwoofer paired to a car audio amplifier but it is a huge plus compared to having no subwoofer integration.

As a general rule and point worth considering, connecting a subwoofer to the car stereo without an amplifier requires an active subwoofer for the best results. It requires plugging in its jack wire with the installed stereo. As we have learnt, connecting a car subwoofer to a car stereo is not a difficult job hence consider doing it by yourself. The results will be wonderful!