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How to Make Subs Louder Outside The Car

Are you disappointed with your sub(s)? Do you want to be heard a couple of blocks away? Do your subs leave something to be desired even when you push them hard? Are you craving that boomy thunderstorm of bass that you can feel and hear?

If you answered yes to any of the questions above, then you’ve come to the right place. In this post, we’ll walk you through a few effective tips that can make your subs louder outside the car.

As bassheads, how a stereo system sounds dramatically determines our perception of it. And while it may seem like making your subs sound louder should cost an arm and a leg, it doesn’t have to.

The tips we listed here are geared for both simple factory systems and more sophisticated setups. Most of them don’t involve massive investment, and you don’t have to spend money on every aspect to beef up your car’s sound and achieve more SPL levels outside your vehicle.


Before moving forward with making these changes, you should check if your sound system isn’t too loud to be street legal, and that you’re not breaking any law. It may come as a surprise to some but you can get an excessive noise ticket (disturbing the peace) if your vehicle’s sound system is too loud.

The laws vary depending on your location, so it’s important to check the rules and ordinances that specifically apply to your state or territory. Generally speaking, anything that is excessively loud without good reason is deemed a violation of the regulation.

What Makes a Subwoofer Loud?

Contrary to popular belief, the “loudness” of a speaker is not solely based on its physical dimensions. Although speaker size plays a major role in its volume capacity, power handling, efficiency, insulation and variety of other variables come into play as well.

Many subwoofers, in fact, are uniquely designed with extremely small physical dimensions, yet are still capable of pumping out clear, rich and loud sound.

Power handling — Wattage

The amount of power – measured in watts – a subwoofers can handle is one of the key variables in the speaker’s production of volume and “loudness”. All subwoofers have a maximum number of watts that they can cope with and it’s the manufacturer will tell you what this is. The total amount of wattage a subwoofer can handle affects greatly how loud it can be turned up.

Usually, manufacturers provide two power figures subwoofers:

  • Nominal power (RMS): What a subwoofer can handle long term without being damaged
  • Peak power : What a subwoofer can handle in short bursts without being damaged

Subwoofer Size

It’s a never-ending question — what size subwoofers play loudest? It’s not an easy question to answer as you need to take into account a variety of things including sensitivity, enclosure type, and power handling.

Though not the only factor, the size of subwoofer plays a significant role in your sound system’s volume as well. Generally speaking, larger subs can move a lot of air than small subs, therefore they can deliver loud and hard-hitting bass.

Regardless of the speaker’s size, however, without enough power juice, the sound system will still be limited by its power. The two factors, therefore, go hand in hand.


Sensitivity – measured in dB – goes hand-in-hand with power-handling to achieve high output. Sensitivity rating measures a subwoofer’s ability to convert the incoming electrical energy into acoustical energy.

A sub that has a high sensitivity rating requires less power to produce the same amount of sound as a model with a lower sensitivity rating.

Enclosure type

There’s a direct relationship between the type of enclosure a subwoofer is mounted in and the type of sound it produces. Generally speaking, sealed boxes render the deepest, most accurate sound, while ported enclosures produce more volume (loudness).

8 Tips to Make Subs Louder Outside the Car

Tip #1: Size matters

As we’ve explained above, there’s a huge correlation between the size of subwoofer and how loud it can play. Car subwoofers range in size from a tiny 6.5 inches all the way up to 18 inches.

If you’re a serious basshead who likes to turn it up really loud and feel that intense, bone-shaking impact of bass hitting your chest, and space isn’t an issue, go for the biggest subs.

That’s not to say that smaller subs are nothing to write home about. Quite honestly, a good small subwoofer will do wonders if properly powered and mounted in a suitable enclosure.

Tip #2: Build a better ported sub box. Or buy one.

Generally speaking, there are two bass camps—those who like it “tight” and those who like it “boomy.” The type of bass you prefer ultimately depends on your musical preferences — and can even vary depending on the style of music.

So, since you’re here, we’re going to assume that you want your bass to boom and you want maximum volume in your music. And for that matter, building a better ported subwoofer box or buying a pre-made one is your best choice.

Ported boxes uses a “Vent” (which is more often cylinder or rectangle shaped) to reinforce low bass response. This vent redirects sound from the rear of the cone and adds it to the sound coming from the front, making the bass louder.

The port also generate an audio effect that is often likened to the sound of somebody blowing through a bottle, and that tonal effect strengthens the note the cone plays.

On top of everything else, in ported enclosures, the sub’s cone has greater freedom of motion.

These characteristics make ported boxes more efficient. The higher the efficiency, the lower the power juice required. In other words, you can use a smaller amplifier than you would need with a comparable sealed box to play at the same volume.

Building a ported enclosure might not be easy or cheap. It takes takes patience, time and a solid understanding of enclosure volumes and other technical terms to construct a good subwoofer ported enclosure.

Not all subwoofers are designed to be mounted in “ported” enclosures. So, if you decide to build your own ported box, make sure you’ve got the right one in there.

You can blow a sub that’s designed for sealed box use by driving it hard in a ported enclosure. It’s also of utmost importance to make sure you’ve got the correct interior volume for the sub you’ve picked out. A mismatch can dramatically reduce performance or even damage your subwoofer.

Filling the enclosure with polyester fiber stuffing is also quite important in making your subwoofer loud; It’ll make your subwoofer think it’s in a bigger box. I know that sound counterintuitive, and you might be asking how does filling a space with material help increase low-end output. Well, the thing is that Polyester fiber stuffing slows down sound waves inside the box, fooling the subwoofer and making it perform as if it’s mounted in a bigger enclosure.

For optimal performance, use 1 to 1-1/2 pounds of stuffing per cubic foot of box volume.

If you don’t want to get your hands dirty and want to save yourself from the hassle of building an enclosure, then you can opt for buying a pre-made one.

Tip #3: Turn the subs facing the trunk not the seats

When it comes to getting loud bass in your car, where you position your subwoofers in the trunk makes a huge difference. Not only where you put the enclosure, but also which way you face the speakers themselves.

Most people think that the best way to experience great bass output is by turning the subwoofer box to face the seats instead of the trunk, which is completely wrong.

Contrary to what most people believe, turning your subs facing the trunk is the best approach to make your subs louder not only outside the car but inside as well due to cabin gain (more on this below). It’s kind of counter-intuitive. You’d think that facing the subs away from you would cause the bass waves to flow out behind the car, but apparently not.

The reason rearward-facing subs yield such impressive results is due to the frequency being an inverse function of wavelength. In other words, the lower the frequency, the longer the wavelength. So, facing your box backwards means the distance traveled is that much further, therefore lower frequencies benefit in-cabin.

All in all, the placement of your subwoofer will depend greatly on your listening preferences. A position that’s not that loud at 45Hz may probably be loud at other frequencies and vice versa.

Tip #4: Run multiple subs

It’s a never-ending question — Are two subs better than one? Well, the answer is typically yes, assuming these subs are of the exact same brand and model. However, comparing different sized car subwoofers, even when they are made by the same brand is nearly impossible.

“Say you compared a Rockford Fosgate 12 inch sub to two of its 8 inch subwoofers. Well, what if the 12-inch subwoofer kind of sucks? Or what if it’s tuned for maximum volume while the 8-inch drivers are tuned for tight bass? Performance differences like these would make the results of a comparison inaccurate and meaningless.”

Given adequate power, a multiple subwoofer set-up will play louder and punch harder because their combined cone surface area yields significantly better and smoother bass response.

Tip #5: Feed your subwoofer(s) enough power

It goes without saying that more power is often better because bass notes are power hungry. With that said, you don’t want to underpower your subwoofer(s) under any circumstances.

Underpowering a subwoofer won’t necessarily hurt the sub – but distortion will. Not giving it enough power just means that your music will lack much of its excitement and detail, therefore, it won’t sound pleasant enough to your ears.

In addition to not underpowering your subwoofer, you should also make sure that the amp you use to power your subwoofer isn’t being overworked and sending out a clipped signal.

The clipped signal, especially one that has been amplified, is a sub’s worst enemy. It can wreak havoc in your subwoofer(s) by making it try to do things it’s not designed to do, which leads to it tearing itself apart or overheating and burning out.

Bear in mind that most car subwoofers – if not all of them – can handle a lot more than their specified RMS ratings, so feeding them a little more power juice than their recommended RMS rating is safe, as long as it’s clean and distortion-free.

It isn’t loudness that damages an under-powered subwoofer, it’s trying to get bass volume by turning up a distorting signal that does it.

Tip #6: Sound deadening material might “LOWER” your SPL

There’s no denying that using sound deadening material is one of the best ways to improve your sound system. It helps with getting rid of noise and vibrations. The latter competes with your music and disrupts your listening experience.

Adding sound deadening material will dramatically improve sound quality in your car. Which part of your car to deaden and which not to depends greatly on your vehicle, so making a blanket statement like “only deaden the trunk and the front doors” is inaccurate.

With that said, if you don’t know the strategic and proper areas to deaden and those to leave bare to achieve the best SPL score possible, deadening the whole car to the extreme amount is your best bet.

Tip #7: Roll down the windows & sunroof

Well, this one is pretty obvious and doesn’t need much discussion. If you want to be heard a couple of blocks away, you need to set the bass notes free by rolling down your car’s windows and sunroof.

Tip #8: Properly tune your subs

It can take a little time and effort to fine tune your subwoofers and get the exact bass sound you want from your subs, but it’s worth it. A well-tuned subwoofer will not only add depth and richness to any type of music, but it’ll also make your subwoofers relatively louder.

To properly tune your subs, here are the steps you need to follow.

Step #1: Properly set your amp’s gain control

Any type of distortion – be it speaker crackling, flapping, crunching, or hissing – is the worst enemy to your speakers, subs, and eardrums. To prevent it, it is crucial that the amp’s gain is properly set.

To do that, start off by playing some music and turn up your receiver’s volume until until the music sounds distorted; then dial down the volume until the music sounds clean again. The current volume level is the maximum volume your receiver can reach and still play cleanly.

Now, it’s your amp’s turn. Try turning your amp’s gain control up slightly until distortion kicks in; then back off the gain slightly until the distortion clears up.

Congratulations, your amp gain is properly set. Now, you can lower the receiver volume to a more comfortable level.

Step #2: Flatten the signal, open the low-pass filter

  1. Next, turn your sub amp’s gain to the minimum level possible.
  2. Switch the low-pass filter on and set it as high as it can go.
  3. If your amplifier has a bass boost, turn it off.
  4. If your amp comes with a remote level control, set it to its middle position. This way you’ll have the choice of boosting or cutting the bass on an individual song later down the road.

Now, let’s move to the receiver side

  1. Adjust your receiver’s bass tone control to zero, or “flat” setting.
  2. If you subwoofer is featured with a level control, set it to “no gain” setting.
  3. Some receivers – especially aftermarket ones – sport a crossover, low-pass filter, or bass boost on their subwoofer output. Make sure all these features are turned off, too.
  4. Sometimes receivers have a crossover, low-pass filter, or bass boost on their subwoofer output. Make sure those features are all turned off, too.

P.S: If both your amp and receiver are featured with the low-pass filters, crossovers, or bass boosts, do not set them on both the receiver and the amplifier at the same time.


Step #3: Adjust the subwoofer gain and low-pass filter

Now, turn the receiver’s volume up to ¾ full and play some music. Turn up the gain on your amp until the sound from the subwoofer completely overpowers the other speakers, without distorting.

Next, keep listening to the music coming out of your sub, and slowly dial down the low-pass filter on the sub amp’s until all the high- and mid-frequency notes are gone.

What a low-pass filter does, is that it passes lows on to the subwoofer, and blocks the notes you don’t want your subwoofer to play. If low filter is set at 100 Hz for example, the amp will block the notes above 100 Hz and only allows those under that to pass.

As a general rule of thumb, always filter out the strings, vocals, guitars, and cymbals. Only the bass and the low drums should be allowed to reach the subwoofer.

Step #4: Adjust the bass boost and subsonic filter

Is your subwoofer amp featured with a bass boost? If so, try to turn it a bit to hear what the bass drum sounds like when you do. Applying just a little bass boost increases the output of low frequencies and brings up the kick a lot.

Keep in mind that if you choose to boost the bass, you will need to re-adjust the amp’s gain, to compensate for the boost and prevent your system from clipping and distorting. If it sounds distorted, lower the sub amp’s gain until it goes away.

If your subwoofer is mounted in a vented enclosure, using your amp’s subsonic filter to tame overly loud low frequencies is a must. This will cut down the levels of the notes at which the enclosure resonates.

It goes without saying that you need to keep tweaking and fine-tuning all the filters until you hear something you like. And when you’re satisfied with how your system sounds, then you can turn the sub amp’s gain all the way down

Step #5: Matching the subwoofer level to the receiver volume

Now that each piece of the puzzle is completed, let’s play some music. But before that you there’s one extra step and that is to match your subwoofer level to that of your headunit.

To do that, start by turning your receiver volume knob up to its maximum, distortion-free position, and slowly turn up your amp’s gain until the bass notes sound balanced and smoothly blended with the rest of your music. And voila!

Final Thoughts

At the end, we can all agree that a good sounding system can make your car turn more heads while you drive past jamming to the beat and we firmly believe that our selection of tips will certainly make your subs louder outside the car.

Bear in mind that sometimes even the simplest improvements to your car sound system can yield impressive results.

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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