6th Order Bandpass Subwoofer Box Design (And Calculator)

Norvan Martin
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A bandpass enclosure will allow you to play only certain frequencies and silence the others. This is a very efficient way of playing low frequencies because it allows for larger drivers in a relatively small enclosure.

Typically, we’re going to talk about “6th order” bandpass enclosures here at BoomSpeaker. 6th orders are characterized by having one port and two speakers (woofers) in series.

The advantage of such an arrangement is that there is no change in polarity across the frequency range. The total number of acoustic outputs (one from each driver) equals the number of ports when impedance increases or decreases through zero at resonance.

6th Order Subwoofer Box Design

The design for this subwoofer box is a 6th order bandpass. A bandpass enclosure will offer the best performance possible at low frequencies as it allows for both front and rear waves to cancel each other out, which greatly reduces resonance that would produce SPL but also introduces “group delay”.

6th Order Subwoofer Box Design layout with measurements

The physical construction of such a box consists of a sealed outer enclosure with an opening cut into it, leaving a membrane between the outer and inner chambers.

Like all ported enclosures, the port needs to be tuned so that box can play a desired range of frequencies without overloading.

In this case, we used the well-known formulae to derive fc (the port frequency) and Qt (the box resonance Q).

  • fc = 1/(2*pi*(Vb/S))
  • Qt = sqrt(WL/CH)

Where Vb is the internal volume of the box, S is the surface area of the port, W is the width of the port, L is the length of the port, and C is the height of the port.

To achieve a response as flat as possible down to 20 Hz, we set fc to 28 Hz and Qt to 0.707. This will give us an enclosure with a -3 dB point at around 27 Hz.

6th Order Bandpass Calculator

When it comes to bandpass filters, there is a lot of calculation that needs to go into ensuring that the filter works as intended. One tool that can help with this process is a 6th order bandpass calculator.

Calculate Your Enclosure

 This calculator will design a 6th order bandpass enclosure. This calculator is only for Qts values from 0.18 to 0.36
 Note : Too much gain can be hazardous to your speakers, try to keep it +3 dB or less.

Enter the Number of drivers, Isobairc loading, Qts, Vas and Fs, then hit Calculate.

Number of Drivers :
Isobaric Loading : Yes    No  
Qts : Vas :  [Ltr] Fs :
Vf =  [Ltr] Vr =  [Ltr]
Fb(F) =  [Hz] Fb(R) =  [Hz]
Passband =  [Hz]
Gain =  [dB]

This calculator can help you determine the appropriate values for your filter, based on the desired parameters. It can be used to calculate the cutoff frequency, ripple, and other factors.

It’s important to note that this calculator is only meant to provide an estimate; you will still need to do some testing to ensure that the filter meets your specific needs. But it can be a helpful starting point and can help you avoid making costly mistakes during the design process.

If you’re looking for a bandpass filter that meets your specific needs, be sure to check out the 6th order bandpass calculator. It can help you get started on the right track.

6th Order Bandpass Ratio

A 6th order bandpass ratio is a measure of how well a filter can separate adjacent frequency bands.

This ratio is calculated by dividing the bandwidth of the desired signal by the bandwidth of the unwanted signal. A higher ratio means that the filter is better able to isolate the desired signal from adjacent frequencies.

subwoofer boxes

There are many applications for filters with high 6th order bandpass ratios. In telecommunications, for example, these filters can be used to separate different signals and improve transmission quality.

They can also be used in electronic equipment to eliminate noise and interference from other signals.

When choosing a filter, it is important to consider its 6th order bandpass ratio. This will help you determine how well it can perform its intended function.

For example, if you need to filter out only one specific frequency, it is better to choose a filter with a high ratio than one with a low ratio.

6th Order Bandpass Design Software

A 6th order bandpass design software can be used to design a bandpass filter with the desired response.

The software can be used to calculate the component values for the filter, and also to simulate the filter’s performance. This can help to ensure that the filter meets the desired specifications.

6th Order Bandpass Design Software

There are many different types of 6th order bandpass design software available, and each one has its own set of features.

It is important to choose a software package that is suitable for your needs. Some packages are more user-friendly than others, while others offer more flexibility in terms of the types of filters that can be designed.

Once you have chosen a software package, you will need to enter the relevant information about the filter. This includes the required center frequency, passband and stopband frequencies, and the type of filter response that you wish to design.

Where Can I Find A 6th Order Bandpass Box for Sale?

A 6th order bandpass box can be found for sale at a variety of different places. Some common places to find them include online retailers such as Amazon and eBay, as well as specialty stores that deal specifically in audio equipment.

It is important to do your research before purchasing one of these boxes, however, as they can be quite expensive.

Make sure to read reviews from other customers to get an idea of the quality of the product before making a purchase. Additionally, it is important to make sure that the box will fit into the space you have available, as they can be quite large.

If you are looking for excellent sound quality and want to purchase a 6th order bandbox, there are several different places you can look. Just be sure to do your research beforehand to make sure you are getting the best product for your needs.

What Does One Get With A 6th Order Bandpass Design?

The answer is, quite probably the best possible performance you can expect from a sealed enclosure.

This is because the 6th order bandpass has 2 air-in and air-out ports. The port tuning frequency (fp) of these ports essentially ‘seals’ the cone in place to prevent it from trying to move at frequencies where it’s no longer needed.

This means that there is very low pressure acting on the cone at frequencies well below tuning which results in very little distortion, fast response, and an almost perfectly linear excursion vs input voltage (xmax) curve.

Theoretically, this would result in an exceptionally high sound quality combined with deep bass extension.

As mentioned earlier, there is a price to pay for all this however and that is the increased complexity of the design.

Not only do you need to calculate and build the box correctly, but also find the right tuning frequency for your specific subwoofer and enclosure size. This can be a tricky process and one which should not be taken lightly.

With that said, if you are up for the challenge and want the best possible performance from your sealed subwoofer enclosure, then a 6th order bandpass design may be just what you are looking for.


As we have seen, there are a few different ways to design a bandpass subwoofer box. The most important factors are the dimensions of the box and the frequencies that you want to pass through it.

In general, the larger the box, the lower the frequencies that will be passed. However, if the box is too large, it will become difficult to move around.

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Norvan Martin is the founder of BoomSpeaker.com. He is a professional Electronics Engineer and is passionate about home theater systems and AV electronics. BoomSpeaker was created as an online hub to share his knowledge and experiences as it relates to home theaters and home audio electronics. My email: [email protected]  Connect on Pinterest and Linkedin