What is a Bandpass Box and the Pros and Cons
(Last Updated On: November 1, 2020)

There are many types of subwoofer boxes out there, but serious bassheads often choose bandpass enclosures.

What are bandpass boxes?

Bandpass boxes are enclosures that house the subwoofer entirely and can produce louder bass at certain frequencies, with tons of slam. There are two chambers in a bandpass box. The first chamber is a sealed box that houses the subwoofer driver. In front of that is a ported box in a separate enclosure. In other words, a bandpass box is a combination of a sealed and a ported design. Bandpass boxes are ideal for genres like hip-hop, hard rock, metal, and reggae.

This design makes the boxes efficient at producing high-quality sound. However, like the other subwoofer enclosures, bandpass subwoofer boxes have disadvantages that you need to consider before making a buying decision. Read on for the pros and cons of bandpass subwoofer boxes. 

Bandpass Subwoofer Box Pros and Cons Table

ProsCons
High EfficiencyResistance to Motion
Low Woofer ExcursionDifficult to Construct
DurableCan Produce Poor Sound Quality
Size VarietyMasking Distortion
Sealed-and-Ported-Enclosure FeaturesBox Can Be Impractically Big

Bandpass Subwoofer Box Pros

The main advantages of bandpass subwoofer boxes are:

  • Highly efficient
  • Low woofer excursion
  • Durable
  • A large box produces a deeper and smoother frequency response
  • Smaller box more efficient
  • Offer sealed-and-ported-enclosure benefits

 

1.High Efficiency

Since the sub’s port acts as a low-pass filter, the system’s high-frequency response is acoustically limited. As the name “bandpass” suggests, the enclosure only allows the right frequency range to be released into the listening environment.

bandpass subwoofer box effeciency

Some people say this makes no difference, given that one can achieve the same by placing a low-pass crossover on a subwoofer. Even though this can work to some degree, a bandpass subwoofer box delivers better efficiency.  

The deep bass extension possible with these enclosures is far better than in conventional subwoofer box designs. If you are interested in getting significant performance without overusing your limited space, the bandpass sub box can be your best option. 

Better still, you can adjust the volumes of your chambers and tune the port (s) to create more outstanding performance trade-offs. You adjust the bandpass enclosure parameters for much narrower bandwidth.

This alone is adequate to have the sub’s efficiency increase and reach 8 dB gains or more. At the same time, by adjusting the enclosure parameters for wider bandwidths, the subwoofer system can produce incredibly low-frequency extension. If this appears to reduce the efficiency and transient response, you can design intermediate bandwidths.

2. Low Woofer Excursion

Bandpass subwoofer boxes also exert the desired control over cone motion. In other words, the box has a low excursion.

Bandpass subwoofer box Low Woofer Excursion

The subwoofer’s cone travels within a short distance linearly from its resting place. This is unique since lower frequency drivers have a high excursion, as they are designed to move lots of air. Given that bandpass boxes have lower subwoofer excursion, they mitigate the risk of pushing drivers beyond their mechanical limits, which is the primary cause of shorter subwoofer lifetime. 

How do bandpass subwoofer boxes exert control over cone motion? The controlled, rapidly changing air pressure on the sides of the enclosure enables the sub to produce high acoustic output levels without demanding too much cone movement.

However, you need to avoid applying much power to reduce the chances of encountering motion resistance. 

3. Durable

Bandpass boxes guarantee the durability of the subwoofer. As we have seen, it gives you great control of sound quality.

You can control the cone to ensure it moves as per the frequency bandwidth that your model is designed to deliver. As such, the enclosure can produce the highest quality sound without getting damaged due to unnecessary tear and wear. 

4. Size Variety

Size matters when it comes to subwoofers. If you install several 8-niche drivers in your enclosure, you can be sure you will have the worst experience. Big is always the best, especially if you are not asking for unrealistic levels of efficiency.

bandpass subwoofer box sizes

With a sizeable bandpass subwoofer box, you get a deeper and smoother frequency response. Since most of these boxes are often much larger than sealed ones, they are sometimes the best alternatives.

Large subwoofer boxes are useful since driving low frequencies requires large amounts of air. A large cone and a large and efficient magnet make this possible.

Consequently, since bandpass sub boxes are often large, they are best designed for reproducing lower frequencies. And the experience is particularly outstanding for individuals who are keen on getting a smoother and deeper frequency response.

Bandpass subwoofers can also give you the best efficiency. To reap this benefit, you must be prepared to use smaller bandpass enclosures even though they hardly pass as wideband frequencies. Given the impact of size on bandpass subwoofer boxes, the enclosures give you the option to choose whether you want a deeper and smoother frequency response or more efficiency.

5. Sealed-and-Ported-Enclosure Features

 Since the woofer is mounted in a dual-chambered enclosure, the box helps get the conventional boxes’ benefits.

The extra booming sound-waves mainly emerge from the ported side. Due to the sound quality that comes within a narrow frequency range, the booming sound is consistent and aggressive, which makes it best for hard rock, reggae, rap, and more.

The sealed features also increase the sub’s capacity to make the sound precise and clean. Overall, bandpass subwoofer boxes often produce louder sounds at particular frequencies’ ranges. 

 

Bandpass Subwoofer Box Cons

The main disadvantage of bandpass subwoofer boxes are:

  • Resistance to motion can destroy it
  • Hard to construct
  • Can produce poor sound quality if poorly tuned
  • Can mask distortions
  • Can be impractically big

 

1. Resistance to Motion

Even though bandpass boxes help subwoofers control cone motion effectively, the same technology can lead to severe damage.

The subwoofer produces high acoustic output levels without forcing the cone to over speed, which makes it less likely to encounter excursion limits. 

However, the cone is moving within the recommended speed does not mean the sub’s motor has stopped from trying hard to increase the cone’s speed.

The motor assembly is designed to ensure the cone moves at the highest speed possible. So, when the sub is not physically moving as much as expected but is producing the required acoustic output levels, the cone encounters lots of resistance, which can be incredibly hard on the subwoofer.

The conflict between the air pressure in the bandpass box and the motor assembly causes motion resistance.

This force often targets the subwoofer’s suspensions and the glue points, and if you apply too much power, it can destroy the drivers within no time. As such, everyone who uses the bandpass subwoofer box must understand how to control the power supply to extend their subwoofer’s lifespan. 

2. Difficult to Construct

Given the intricate design of bandpass subwoofer boxes, the designer must be equipped with advanced skills to construct it.

The rules governing the construction of these enclosures leave no room for error. A minor mistake, such as a sloppy construction or a slight volume miscalculation, can turn your investment into a non-performing enclosure. 

bandpass subwoofer box construction

Without the right sized-port or ports, the box cannot help you. The challenge is that integrating these vents is difficult. 

The woofer is entirely inside the box, and the designer must make an airtight access panel for service that can make work easier in case of woofer failure.

If one fails to follow the manufacturer’s instructions, the woofer may get damaged or fail. Therefore, the design of bandpass subwoofer boxes should be left to experienced pros.

3. Can Produce Poor Sound Quality

The efficiency of bandpass subwoofer boxes can increase when you adjust the enclosure parameters for narrower bandwidth.

Unfortunately, if you adjust the box parameters for wider bandwidths, the efficiency and the transient response reduces.

In other words, individuals who want to get quality low-frequency extension often opt to adjust their enclosure parameter for wider bandwidths, but they end up sacrificing this critical feature.

4. Masking Distortion

Since the woofer is inside the inner chamber, the box can mask distortions.

The worse part of it is that you may never notice distortions that can damage the woofer. Although these boxes are known to be incredibly durable, if you lack the skills to monitor cone motion and listen to identify the main signs of distortion, the lifespan may drastically reduce.

In other words, with this box, you need to have the ability to choose the required amount of power and set amplifier gains appropriately.   

5. Box Can Be Impractically Big

As we have said, size matters when it comes to subwoofers. However, whichever size you choose, you are most likely to lose something valuable.

large 8th order bandpass box

For example, if you choose a large bandpass subwoofer box, you will not get the best efficiency if you are trying to pass many low frequencies.

But you can get the desired result if the box is much bigger. So, you may face the challenge of dealing with impractically bigger boxes. 

But using small enclosures does not guarantee you a smooth frequency response in the frequencies they pass.

So, some sound frequencies will be louder than others. But smaller bandpass enclosures are more efficient, and larger ones produce smoother and deeper frequency response, but they have drawbacks. So, you have the option to use bigger boxes if you want a deep and smooth frequency response, but you may need too big boxes to get the best experience.

 

Conclusion

Bandpass subwoofer boxes are specially created for maximum boom. Designers carefully mount the woofer inside the dual-chambered enclosure, and the sound waves emerge from the ported side or sides.

The aggressive sound is great for hard rock, reggae, and rap. But the boxes are not suitable for some subwoofers. For that matter, before making your buying decision, consider these pros and cons to be able to choose a bandpass subwoofer box that best suits your needs.