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How to Install Underseat Subwoofer?

Are you looking to add some bass and thump to your car’s sound system with no space wasted? The simplest way to do it is by installing an underseat subwoofer.

With underseat subwoofer, you can make the most out of a limited amount of space while still adding strong low-end response.

To install an underseat subwoofer in a car:

#1. Disconnect negative lead from the car battery before starting.

#2. Remove the head unit by unscrewing and detaching all wiring harnesses.

#3. Use RCA cables to connect the subwoofer output to the head unit and the remote turn-on lead.

#4. Choose suitable spot under the seat and secure the subwoofer in the location.

#5. Reattach the head unit, attach wiring harnesses, and connect the remote controller.

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Tip: If you are looking for a high-end underseat subwoofer for softer music types, I recommend checking the 8″ Focal IBUS20 (link to Amazon).

It fills missing low tones perfectly but is not a sub for bass-heavy music.

In this article, I am going to guide you through the installation process of an underseat car subwoofer.

How Do I Install My Underseat Sub? A Step-By-Step Guide.

A subwoofer upgrade is a great way to enhance your car’s sound system.

With the right subwoofer, you can improve your car’s audio system’s sound quality and add some much-needed bass output to your factory stereo.

#1. Disconnect the Battery

It is essential to disconnect the battery before working on the electrical system of your car.

The first step is to disconnect the negative terminal of the battery using a basic tool like a socket wrench.

Then, although not always needed, you can disconnect the positive terminal. This will prevent electrical shocks or accidental power shorts while working on the system.

#2. Install the Power Wire

The next step is to install the main power wire. This wire is responsible for providing power to the subwoofer and the amplifier. 

To install it, you need to run it from the battery to the subwoofer through the firewall to the main cabin.

You will also need to install an inline fuse, which for safety reasons, needs to be placed as close to the battery as possible.

#3. Run the Power Wire Through the Firewall

The best way to run the power wire through the firewall is to use an existing grommet unless you need to drill a hole in the firewall.

This will allow you to pass the wire through the hole and bring it out under the driver’s side of the steering wheel.

After the wire is out of the firewall, you can run it up and away from the pedals or under the center console, securing it as you go.

Once you have the power wire run, you’ll be ready to start wiring up your subwoofer.

#4. Connect the RCA Wires to the Subwoofer

To connect the subwoofer, connect the RCA signal cables to the back of the head unit, usually labeled as “aux out” or “RCA out.”

#5. Install the Subwoofer

After you have your subwoofer wired up, you can install it on either your or passenger side.

Make sure that its position is stable and secure and that you’ve got the size of the subwoofer, the location of the seat, and the orientation of the subwoofer all correct.

Which Are the Best Underseat Subwoofers?

I am sure you have seen many underseat subwoofers available in the market. How to decide which one is better for your vehicle?

When selecting an underseat subwoofer, there are several factors to consider.

I am sure you want a good subwoofer that produces deep bass without distortion and fits nicely under your car’s seat. 

You also want the subwoofer designed for the type of music you listen to and has a good power handling capacity.

The best underseat subwoofers are active ones, meaning they have built-in amplifiers. They may not be as powerful as large subs in trunks, but if you do not have room in the car, there is no better option to add the lowest notes to your music.

Below I listed my three top pics when it comes to size, power, and also price.

#1. KICKER 46HS10

The Kicker 46HS10 (link to Amazon) is a compact, powered subwoofer with a low-profile design that packs a punch thanks to its 10″ speaker and built-in 180-watt amplifier.

It is the most powerful one of all I recommend but also the most expensive one.

Kicker 46HS10 Powered 10-Inch Subwoofer w/ 6.5" Coaxial Speakers & Amp Kit Bundle. Hideaway Compact Amplified 10" Car Audio Sub, 180 Watt RMS, w/ 46CSC654 CS Series Speakers & Copper Stinger Amp Kit

With its all-aluminum chassis and stylish metal grille, the HS10 is tough and looks great. In addition, the HS10 is designed to fit almost anywhere and can be installed under most seats to bring the bass right up close to the listener.

One of the great things I like about the HS10 is its adjustability. The subwoofer features a low-pass crossover, a subsonic filter, a phase switch, and a variable +6 dB bass boost that you can adjust with the included remote control.

The HS10 also offers two auto turn-on options and a wiring kit for easy installation.

For those looking to use the HS10 in their car, the subwoofer can accept input signals from 0.25 to 40 volts, making it compatible with almost any vehicle without needing line output converters or RCA outputs.

The speaker also features high- and low-level inputs, giving you plenty of options for hooking up your subwoofer.

KICKER 46HS10 Car Audio Hideway Compact 10" Slim Powered 300W Sub Box Enclosure

The HS10 is an excellent option for a compact, powerful subwoofer that can make a deep bass. With the frequency response starting at 25-120 Hz, you can feel the front seats shaking.

Overall, the Kicker 46HS10 is an excellent compact subwoofer that delivers impressive bass response and has a wide range of adjustability to suit your preference.

It also blends seamlessly into the interior of any car and is undetectable from the exterior.

Pros:

  • Compact and powerful
  • Adjustable settings
  • All-aluminum chassis and stylish metal grille
  • Easy to install
  • Compatible with almost any vehicle

Cons:

  • The remote wire may be too short for larger cars or when the sub is installed under the rear seat.

#2. Rockville SS8P

The Rockville SS8P (link to Amazon) is a game-changer if you are looking for more bass in your car without taking up a ton of space and do not want to spend too much money on the sub.

This all-in-one subwoofer is only 2.8 inches thick, making it perfect to fit under your seat.

One of the standout features of the SS8P is its sleek design.

Rockville SS8P 400w 8" Slim Under-Seat Active Powered Car/Truck Subwoofer Sub

The enclosure is made of cast aluminum, which keeps it cool to the touch, and the heavy-duty mounting feet make it secure and stable.

This subwoofer packs a strong punch with 400 watts of peak power and 100 watts RMS, but it is not as strong as the above Kicker.

My favorite part is the range of sound controls. Those include a level control for volume, subsonic filter, low pass crossover filter, phase control, input sensitivity, and bass boost, which allows you to customize your listening experience to your liking.

The SS8P includes high-level aftermarket and factory systems inputs, so you can install it even if you don’t have preamp outputs.

The smart turn-on circuit automatically detects when an audio signal is present and turns on the amplifier. Likewise, when you turn off your music signal, the amplifier automatically turns off. 

Wiring is straightforward, with all the inputs and outputs on one side, and the package even includes a remote bass knob and mounting hardware.

Rockville SS8P 400w 8" Slim Under-Seat Active Powered Car/Truck Subwoofer Sub

I heard a few people saying it sounds weak when placed under the seat, and I agree. 

Well, it is a small shallow sub, so do not expect it will shake your car, and if you’re looking to blast your music to the max, this subwoofer might not be the best fit for your needs.

All things considered, the Rockville SS8P is an incredible budget option.

It’s easy to install, packs a serious punch, and has many features to make your listening experience as enjoyable as possible.

And let’s be honest, isn’t that what it’s all about?

Pros:

  • Easy to install
  • Compact and slim design
  • Integrated amplifier
  • Range of sound controls
  • Affordable

Cons:

  • Not suitable for high power system
  • It may sound muffled when placed in a tight spot under the seat.

#3. Kenwood KSC-SW11

The Kenwood KSC-SW11 (link to Amazon) is a compact and powerful subwoofer that can fit under a car seat in more vehicles than both earlier options.

In simple terms, it is the smallest one, with a cone size close to the typical 6×9 speaker, but do not be mistaken by the dimensions.

Kenwood KSC-SW11 Compact Powered Enclosed Subwoofer for CAR (Renewed)

Despite its small size, it delivers impressive bass.

Design:

  • The KSC-SW11 features a small, rigid aluminum enclosure that eliminates rattles and is durable.
  • Measuring 11″W x 2-3/4″H x 7-1/2″D, it is small enough to fit in many tight spaces.
  • The enclosure houses an 8-1/4″ x 5-1/8″ subwoofer designed to produce a low-frequency response equal to that of a larger subwoofer.

Functionality:

  • The built-in amplifier feeds the speaker 75 watts of RMS power (150 watts maximum)
  • Wired remote for control over volume level, variable low-pass crossover (50-125 Hz), and selectable phase control (0°, 180°)

Features:

  • Power and ground wire harness and preamp-(RCA) and speaker-level inputs
  • frequency response: 35-125 Hz

Regarding personal experience, The Kenwood KSC-SW11 is a wonderful piece of equipment, it’s not a ground-pounding sub, but it nicely fills the cab with bass.

The remote is super helpful for a song to song tuning.

The frequency range does not go as low as in the above Kicker. It stays within a strong 6×9 speakers range, but it still can make mirrors shake. 

When it comes to the installation, the only installation issue I had was with the power cord.

The harness has a built-in fuse box which was impossible to fit through the grommet, so I had to cut the fuse and install a new one on the engine compartment close to the battery.

Overall, Kenwood’s KSC-SW11 powered subwoofer is a great option for those looking to add extra bass to their car audio system without taking up a lot of space.

It is compact, powerful, and easy to use, and the built-in amplifier and wired remote make it convenient to adjust the bass to your liking.

Pros:

  • Compact size, suitable for tight spaces
  • Built-in amplifier and wired remote for easy control
  • A rigid aluminum enclosure eliminates rattles.
  • Amazing bass response
  • It comes with a wiring harness and mounting brackets.

Cons:

  • Not suitable for those looking for ground-pounding bass
  • The built-in fuse of the power cable can be difficult to fit through some car grommets.

Conclusion

Installing an underseat subwoofer can significantly enhance your car’s audio system, and many options are available.

It’s important to choose a subwoofer that matches your vehicle’s size, your preferences, and your budget.

The installation is straightforward, and with patience, the right tools, and good instructions, you can do it all by yourself in less than an hour.

FAQ

What Are the Differences Between Powered and Passive Subwoofers?

Powered subwoofers come with a built-in amplifier, while passive subwoofers require an external amplifier.

Powered subwoofers are more convenient to install and use, while passive subwoofers give you more flexibility in terms of amplifier choice and power output.

Can I Install an Underseat Subwoofer in My Car Without an Amplifier?

It depends on the type of subwoofer you choose. Active or powered subwoofers have a built-in amplifier so that you won’t need an additional one.

However, passive subwoofers require an external amplifier to function.

If you want to install a passive subwoofer, you will need to purchase an external amplifier, as the stereo is not powerful enough for subwoofers.

Do I Need Special Tools or Skills to Install an Underseat Subwoofer?

You only need standard tools such as drills, screwdrivers, wiring kits, and some measuring tape.

If you’re comfortable working with electrical wiring and basic tools, you should be able to install an underseat subwoofer on your own.

However, if you’re not comfortable working with electricity, it’s best to consult a professional.

Why Does My Underseat Subwoofer Not Turn On or Produce Any Sound?

Problems with power may be caused by caused with the power cable or the fuse.

Make sure that the power cable is properly connected and that there are no loose connections. Check the fuse holder and make sure the amp fuse is good.

Another possible cause is that the remote turn-on wire is not connected correctly. If this is the case, connect the remote turn-on wire to the head unit or the factory amplifier.

How Can I Improve the Sound Quality of My Underseat Subwoofer?

To improve the sound quality, try adjusting the gain and crossover settings on your amplifier or adjusting the volume level on your head unit.

If you’re using a passive subwoofer, you can also try different amplifier settings to fine-tune the sound quality.