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8 Creative Ways to Secure Your Subwoofer Box in The Trunk

We often get asked for tricks on how to improve bass and how to make subs sound louder in a vehicle. However, one of the most overlooked aspects when installing a subwoofer box into a vehicle is making sure it doesn’t move around.

A subwoofer can release a tremendous amount of energy when it’s hitting hard, so if the enclosure isn’t fastened down tight, it will actually move around as the bass notes hit, or during hard, fast cornering or when you make a quick stop.

This causes a loss in bass energy and can result in somewhat decreased bass output as well as inaccurate response. Fastening the enclosure down can prevent this and allow for a better sounding bass.

Is It Safe To Drive With A Subwoofer Box?

In sedans, it’s completely safe (but NOT recommended) to drive with an unsecured subwoofer box. This is because the trunk is separated from the cabin.

However, if you’re driving a SUV, a station wagon, or a hatchback, then it’s not really safe to have an unsecured box in the trunk. This is especially true when the cargo cover is removed.

I mean, think about, if you’re driving at 55 miles per hour, every object in your car is traveling at the same speed.

At that speed, a 20-pound object hits with 1,000 pounds of force — so powerful that it could turn into a deadly projectile that could cause some horrific injuries or even death if it strikes you during a collision.

Many studies have shown that many drivers are increasing the risk of injury or death in car accidents by leaving items unsecured.

In fact, according to Safety Research and Strategies, it has been reported that unrestrained items in vehicles are responsible for approximately 13,000 injuries annually.

Sadly, many drivers are completely oblivious to the dangers of loose items in a car. In one report, a medium-sized cooler located in the trunk of the vehicle flew forward and crushed the rear passenger. The severity of the impact caused the cooler to continue its forward motion, hitting the driver and causing severe injury.

Although it is not always possible to avoid a collision or a car accident, as a driver you can take a few steps to minimize the risk of injuries caused by unsecured loose objects inside your vehicle.

So, take no chances. Here are a few different ways to secure your subwoofer box back there.

8 Ways to Secure a Subwoofer Box in Trunk

Subwoofer boxes are great, but they have one major downside – they can slide around in the trunk when driving.

An unsecured subwoofer box can be noisy and annoying. It can also be a literal headache, and simply unsafe.

Luckily for you, we’ve gathered some tried and tested ways to prevent your subwoofer box from sliding in your trunk either when driving the car really hard or in the worst situation, being in an accident.

1.  Bolt the Box Down

The safest way to hold a subwoofer box tight in the trunk is to bolt it down directly into the floor of the vehicle. So, how to bolt down a subwoofer box?

Well, what you need to do is to drill four 1/2-inch holes in the box corners, and run strong bolts with large fender washers through the bottom of the enclosure and bolt it directly through the floor of the vehicle.

Drill holes that are just large enough to run the bolts through and then put a bead of silicone or similar sealant around the washers inside the enclosure to prevent air leaks. Then use washers and nuts under the vehicle so the bolts do not loosen up.

Furthermore, you may need to lay some neoprene between the metal and enclosure to decouple it from the car and to prevent unwanted buzzes/resonances and noise that occurs when two hard surfaces are brought together.

Bolting down your subwoofer box is highly recommended for a variety of reasons. First, it’ll make the box somewhat theft-proof. That is to say even if a thief breaks into your car, he can’t jack it as easy. Second, if you ever get into a car accident your sub box won’t turn into a deadly projectile that flies forward towards you.

Bolting your subwoofer box down would also keep it from sliding around, possibly causing damage to your equipment.

The main downside to this method is that it will be difficult to remove the enclosure should you need some cargo space.

P.S: Make sure your vehicle does not have wires, fuel lines, or a fuel tank under the location for drilling.


2. Use Metal “L” Brackets

If you do not wish to drill through the vehicle, another great option to keep your subwoofer box from sliding around is to bolt metal “L” brackets to the cargo floor of the vehicle and then through the enclosure.

All you need to do is to screw one end of the bracket into your sub box and the other end into the wooden tire cover using self tapping metal screws.

How many brackets you’ll need depends on how large your subwoofer box is. Generally speaking, 2 to 4 strong L brackets would be more than enough to hold the box and prevent it from sliding around the trunk.

The main downside to using L brackets is that they restrict access to the spare tire compartment. In other words, if you have to take your spare tire out you would have to unscrew the L brackets.

P.S: To make it easier to unscrew the L brackets, use wing nuts.


3. Use Swivel Hasps

Swivel hasps can be used for a wide variety of things including doors, cabinets, boxes and trunks. You can also use them to mount a subwoofer box in the trunk.

Using Swivel Hasps is essentially identical to using L brackets. However, the biggest advantage to swivel hasps is that they make it really easy to remove the box and to put it back in the trunk in no time. Best of all is that you can use them with a lock to prevent subwoofer box theft.

4. Use Door Hinges With a Removable Pin

Using small doors hinges is another great way to mount your subwoofer box in the trunk. So, essentially what you need to do is to screw one side of the hinge to the back of the box, and screw the other side of hinge to the floor, and then then slide a pin through it to hold the box.

Depending on how large your subwoofer box is, you may need to use multiple small door hinges.

Now, to take the enclosure out of the trunk, all you need is to remove the pins out of the hinges.

5. Hold it Down With Tie Down Straps

If you do not wish to drill into your enclosure itself, you can attach a few brackets to the cargo floor or interior metal and then use an adjustable tie-down strap to hold the enclosure in place.

While this is not quite as secure or as safe as the other methods, it is still a much better option than leaving the enclosure loose. It is also nice in applications where it is often necessary to remove the enclosure to accommodate luggage, grocery, etc. that require more trunk space.

6. Use Heavy-Duty Velcro (Double Sided Velcro)

Using heavy-duty double sided velcro can also get the job done, no muss no fuss. This is especially true if your sub box isn’t too big.

So, just throw down two or three strips of velcro on the bottom of the box (claw side down), and it won’t budge.

Make sure to staple the hook sides of Velcro straps around the bottom corners of your subwoofer enclosure. And do not attach the fuzzy side of the velcro to the trunk mat. The hooks will grip firmly onto the floor mat.

For safety purpose, it’s not recommended to use velcro if you’re driving any sort of SUV/Hatchback/Wagon.

A subwoofer box that’s secured down using Velcro – no matter how strong it is – can come loose in a wreck and cause serious injuries. So, take no chances.

While this is not quite as secure as the other methods that involve using brackets, hinges, bolts…etc, it is still a better option than leaving the enclosure loose.

7. Use Adjustable Buckle Strap

Another decent method to secure down your subwoofer box in the trunk is to use adjustable buckle straps with screw attachments on one end.

So, attach the end with screw attachments to the enclosure, and tie the other end to a spring clip and attach it to child seat anchor points.

These adjustable straps come with a snap clip in the middle of the strap for quick release.

8. Use a False Floor

If you don’t wish to drill into the factory spare tire cover, then make a 1/2″ thick MDF copy of it, carpet it and put it in your trunk.

Now, install your box and drive a couple of bolts or screws from the bottom of your enclosure into the new floor you made.

This will allow you to remove it all and replace it with the factory spare tire cover when you need to transport things.

What to Look Out for When Mounting a Subwoofer in the Trunk

It goes without saying that you always need to check your trunk space before you buy your subwoofer enclosure. This is especially true in small vehicles where space is at a premium.

Furthermore, make sure your sub enclosure isn’t going to be pain in the ass should you need to remove it. I mean, if you often need to use the trunk space taken by your sub enclosure, or that your spare tire is right below the sub box, then your sub box should be easy to unmount.

Being easy to unmount shouldn’t be understood as being loosely attached. As mentioned above, an unsecured subwoofer box can cause serious injuries or even death in the event of an accident.

Additionally, if you decided to bolt your subwoofer box down, it’s of paramount importance to check that there are no wires, fuel lines, or a fuel tank under the location for drilling.

Alex Brown

Hey There, my name is Alex Brown, I'm an LA-based sound engineer with over 10 years experience installing, troubleshooting, and repairing commercial, automotive, and household sound equipment. I've installed highly competitive car audio systems, and everything from navigation systems to full car stereo systems, remote starters, alarms and beyond. I enjoy creating solutions and simplifying everyday needs. I also love helping people get great sounding gear, thereby, saving the world from bad sound one customer at a time.

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