HERE’S Why Your Subwoofer is Bottoming Out (And How to FIX It!)

Subwoofers are complex devices; they can be hard to set up and maintain in both critical and appreciative listening scenarios. This explains why some engineers and even audio enthusiasts will always try to avoid it. 

One very annoying and undesirable scenario for anyone into audio would be racking your brain trying to find out exactly why your subwoofer is giving out a terrible and “hard-to-describe” sound. 

Even in professional audio instances, bass and subwoofer management can both be financially and technically demanding. A typical example is how much stress it takes to calibrate subs in  home studios (not all cases). 

Also, acoustic requirements for subwoofers and bass frequencies can be pretty intimidating, especially to newbies in the audio field. As if the aforementioned problems were not enough headache already, you are not faced with “bottoming-out” issues. 

For some people, they are not sure of what they are hearing; they just know that their subwoofer is sounding terrible. On the other hand, some know what exactly is the problem; they know their sub is bottoming out. But, they also do not know the solution(s). 

Whatever the case is, subwoofer bottoming out is not an ideal and fun experience, technically and acoustically—-it is just terrible. 

For people who do not know what it means for a subwoofer to bottom out, this article will explain that. We will not only let you know what that means; we will also cover possible fixes and practical ways you can manage this horrible audio situation. 

Simply, subwoofer bottoming out means that your sub’s subsonic filter is struggling to maintain just the right amount of bass response to keep up with the required bass sound. 

This means that your subwoofer is trying to exceed its excursion limits while trying to reproduce low bass at high volume. 

Subwoofer Bottoming Out in Detail – What Does it Mean?

To better understand what bottoming out means in the context of a subwoofer there are a few terms you should familiarize yourself with. 

These will bring into perspective the various components of the subwoofer that are involved in a scenario where it is “bottoming out” and will also tell you about certain behaviours of the subwoofer that constitute “bottoming out.”

Subsonic Filter

This is a filter designed to stop very low-frequency sounds from reaching the subwoofer. Typically, this kind of filter can be found on sound-processing devices like amplifiers and DSPs.

Excursion Level

This is how far the cone of the speaker moves back and forth from its resting position. Too much cone movement is known as over-excursion.

Motor

This refers to the magnet at the end of the subwoofer.

Voice Coil and Cone

These are the two moving parts of the subwoofer. The voice coil sits partly inside the magnet and partly under the cone. 

The cone is the big visible area on the top of the woofer and is being pushed back and forth by movement in the voice coil. It is these movements of the cone that create the sound that we hear from the subwoofer.

What Is Bottoming Out?

Bottoming out is a mechanical phenomenon that can happen to any kind of speaker, but it is very apparent with woofers. Moreover, due to the kind of sound frequency that woofers are exposed to, they are most likely to bottom out. 

This happens when the moving parts in the woofer (voice coil and cone) go beyond their physical limitations. 

More specifically, the voice coil oscillates more than it should within the magnet causing over-excursion in the cone, thereby causing extra stress on the entire structure of the woofer. 

Of course, in such a situation, the woofer is not producing any good quality sound since there is distortion. However, other than bad sound, bottoming out can also result in serious damage to the woofer. 

How Does A Bottoming Out Subwoofer Sound?

Here is a great video demonstrating what a regular subwoofer sounds like when it bottoms out. 

The important thing to note here is that different subwoofers will sound different when they bottom out. In general, when subwoofers bottom out, the sound can best be described as a ‘clacking’ or ‘clanging’ sound. 

This is because the metal voice coil is physically striking against the magnet behind it. Amidst the loud bass that you are hearing, you will also hear a sharp metallic striking sound which tells you that the subwoofer is going through over-excursion and the voice coil is hitting the motor. 

When it comes to bottoming out, in most speakers the bass itself will also start to become distorted and it will become softer. The bass will not have the same punch to it since the cone is over-extending itself.

This compromises the quality of the bass that you hear. Moreover, the material used in both the cone and the voice coil plays a role in the kind of sound that is created when it bottoms out. 

Another thing to keep in mind is the specific kind of speaker technology that your woofer may or may not have. 

Traditional woofers, such as entry-level woofers designed for car audio or mid-tier subwoofers designed for home use, usually don’t have any advanced hardware that limits bottoming out. 

However, when you move to commercial speakers and larger subwoofer systems it is quite common to find limiters on such systems. 

As the name implies, the limiter is designed to limit the amount of bottoming out that goes on. In this case, you will not hear a hard bottom but rather a soft bottom since the voice coil is physically limited in its movement to protect it from slamming into the magnet underneath. 

Moreover, the cones may also have a protective layer to prevent over-excursion which could damage or even tear the cone apart. 

In high-end SQ subwoofers and even SPL subwoofers, electronic limiters are also used. These electronic limiters prevent the subwoofer from being overdriven. 

In this case, if you push the subwoofer too hard, you may notice that the sound just becomes flat or simply distorted since the device is limiting power output to the driver to prevent physical damage. 

After all, having the hardware smash into itself will cause damage to the overall system and in particular, will damage the former severely. 

On some systems, the bass will get a lot more ‘whooshy’ and sound very mixed and spaced out rather than being compact, tight and on-point. 

This is particularly true for subwoofers in sealed enclosures. They start to sound like they are in a box with a port that is far too large for that woofer size.

What Causes a Subwoofer to Bottom Out?

In nearly all cases, bottoming out occurs because the subwoofer is being pushed beyond its physical capabilities. Bottoming out is most common in situations where the sub is getting a lot of gain.

Also, it can happen when the bass boost is pushed to the max setting, or even if the overall system is being played at a high volume. Each situation will have its implications. However, the cause of bottoming out can vary depending on the specifics of the setup. 

Poorly Configured Filters

Here is a video discussing the impact of filter configuration on subwoofer performance. 

Filters play a big role in car audio and other systems where the subwoofer is being fed through an external amplifier. In the world of home theatre and home audio setups, this is less common since they use an active woofer or one with an amp built in. 

External amplifiers can output a lot more power than inbuilt ones and pushing an external amp to its peat wattage output can easily push a subwoofer well beyond its mechanical capabilities leading to bottoming out. 

The best strategy in this case is to properly configure the HPF and LPF filters. Failure to configure these settings will cause extremely low frequencies to reach the woofer which can cause bottoming out. 

Gain And Volume

Here is a video discussing the impact of high volume on speakers and subs. Subwoofers are designed to play low frequencies. However, extremely low frequencies are dangerous; they are even more dangerous when played at very high volumes or high-gain settings. 

The sub requires a lot more power to make very low frequency audible at high volume. As it draws in so much power to produce the bass frequency, the voice coil and cone can overextend and cause bottoming out. 

Woofer Box Design

Here is a video discussing poor enclosure design and its impact on subwoofer performance. 

The woofers enclosure also plays a big role in how much flex the cone experiences and how much movement the voice coil is exposed to. Moreover, in ported enclosures, the tuning of the port also impacts the movement of the subwoofer parts. 

This is a bigger problem in cases where the sub is installed in an after-market or custom-made box. Woofers that come with factory enclosures have properly tuned enclosures and there is less of a chance of bottoming out in them. 

If an enclosure is too small for the woofer, if it is too big, or if the port tuning isn’t right, they can all result in bottoming out. 

Mismatched Components

Here is a video discussing how you should match components and specifically external amps and subs. 

Building an audio system is not just about getting the best components; it is also about getting components that will gel together smoothly. When the power requirements for different components are vastly different, it can overdrive some while underdriving others. 

This is particularly true for components like subwoofers which tend to draw very high loads very quickly and in abrupt rhythms.

How to Fix Bottoming Out Subwoofer

If you are facing a bottoming-out issue, the best strategy is to get to the root of the issue and resolve what is causing it. However, there are a few other general ‘tips’ that you can keep in mind when going for a fresh build to help protect your sub. 

If you are currently facing bottoming-out issues, these are some of the main areas you will want to look at to make sure you are doing things right in these departments. 

Build The Right Enclosure

Here is a great video covering all the main areas of building the right enclosure.  If you are starting with a raw subwoofer, you need to build it into a box.

Whether you choose to go with a ported box or a sealed box will depend on your needs, and also to some extent on what the woofer is designed for. 

Going with what the sub is designed for will give you optimum sound, but if you are just after volume or you just prefer a different kind of box, that is also very manageable. 

Building a box is quite straightforward, but you need to do your homework to get it right. Making sure you have the right measurements and the right design will make all the difference. 

If you want to avoid this issue, you could always go with a sub that comes prefabricated in an enclosure. 

Proper Band Settings

Here is a video covering everything you need to know about band settings on your amp. 

Setting the LPF and HPF settings is one thing, but when you are dealing with high-power subs and amps, there are additional settings to look into as well. These are settings such as bass boost, bass frequency and phase shift. 

Once you understand what these settings do and how they are changing the sound on your system, you need to tinker around with them a bit to get it just right for your system and your liking. 

There is no right or wrong way with these settings, however, you do need to make sure you are removing any unsafe frequencies going to your subs.

Upgrade When Needed

Here is a video discussing a one-sub setup Vs. a two-sub setup as well as the differences between small and large subwoofers. 

If your sub is bottoming out, you might just be pushing your subwoofer too hard. Keep in mind that more power will not just get your sub louder, it will push it beyond what it is able to handle. 

If you feel like you aren’t getting enough bass, or bass that is evenly spread around the listening area, or you just want louder bass, it will be a good option to upgrade your setup. This can be done by adding another sub or it can be done by getting a bigger subwoofer. 

How to Break in A Subwoofer

One of the best things you can do to ensure your woofers perform optimally and remain in top shape for many years to come is to break in your woofer. 

Breaking in essentially involves playing specific kinds of audio and certain volume levels for several hours to allow the speaker to take its full form. When you receive a woofer straight from the company, it is going to be stiff and the components will be completely fresh. 

In this condition, the woofer will not perform at its best since it doesn’t have the flexibility for good excursion and therefore cannot produce sound optimally. 

The aim is to make the cone, the spider, the voice coil and all other dependent parts fluid in moving together and also getting them to reach their full flexibility without causing damage. Breaking in the woofer is a 3-step process. 

In the very first step, you are going to play the woofer at 30%-40% volume for 18-20 hours. You don’t have to play it continuously for 18 hours straight but rather just get a total run time worth roughly 20 hours. 

During this phase, you want to play some music that has heavy bass. Something like techno, house, hip hop, rap, afrobeats, and other bass-heavy genres will give the woofer plenty of stretching. 

After the first phase, you want to pump the volume up to 60% and allow the woofer to run for another 12 hours. Again, you can run the woofer for an hour at a time or even smaller intervals to get a full 12 hours played at this higher volume level. 

Lastly, you want to play the woofer for another 10-12 hours at 80% volume for it to get even more movement happening and to stretch everything to the max. 

This will cause a very noticeable change in maximum dB output and will also make the bass delivery a whole lot smoother. Moreover, with everything properly broken in, you run a much lower chance of tearing a cone or burning a coil. 

When breaking in, make sure you have the woofer installed in the enclosure you plan on using the woofer in later on as well. This will give the woofer the proper break-in in the conditions that it will be exposed to regularly. 

Subwoofer Port Noise vs. Bottoming Out – What are the Differences?

Here is a good video that shows what port noise looks like and sounds like. This video demonstrates what bottoming out sounds like. 

Port Noise

Some people confuse port noise with bottoming out. Simply put, port noise occurs when the amount of air leaving the enclosure of the subwoofer doesn’t have enough space through the port and this causes the air movement to create noise. 

It’s a bit like what happens when air rushes out of a fully inflated balloon and causes a very slurpy noise like the wind is ‘bubbling’ out of the balloon. 

The same thing is happening with the port on your subs enclosure. There isn’t enough room on the port to move the volume of air that the sub is putting out, so it causes noise. It can also be a sign that your sub is overextending and causing more airflow than it should. 

Also, it could be a sign that your box simply isn’t tuned right or it is just too small for your sub, at least at high volumes when it causes port noise. 

Bottoming Noise

Bottoming occurs when the movable elements of your sub are moving too much and hitting other internal parts. In most cases, this is going to be the voice coil and the former hitting against the magnet or even hitting against the suspension of the subwoofer. 

In rare cases, it can even be the cone slapping against the spider of the sub. In any case, the over-excursion causes parts to hit each other which then causes the bass to be distorted and also adds a metallic clanging sound whenever different parts hit each other. 

Conclusion

If you enjoy listening to loud bass on a ported sub, then bottoming out and port noise are both things you can expect. 

However, if you do your homework, create the right box, tune it properly, and properly break in your sub before putting it through its paces, you can save yourself the discomfort and the cost of damaged subs. 

Moreover, you can optimize your listening experience and get the most value from your system. Luckily, both of these issues are not very difficult to fix and with the solutions provided in this article, you should quickly be on your way to creating ground-shattering bass.