How to build a subwoofer box with port

How to build a subwoofer box with port DEFAULT


Getting Started

This 4 step process will show how to design a subwoofer system for your vehicle. For many, this seems like a daunting challenge for mathematicians and alchemists, blending the acoustic voodoo arts with the Pythagorean Theorem. Its really not that hard, and before you bail on the idea in favor of calling on someone to do the work for you, read on a bit and have some fun designing your own system.

The benefit of doing the design yourself is you get to call all the shots; you get the system done like you really want. We have spent years working on the acoustic/enclosure design of the equation, leaving you to enjoy the creative side of your system design.

Our DDBox system takes all the guesswork out of the sound produced, just follow the size/port charts and formulas. Keep in mind that airspace is what makes the bass. Follow the hyperlinks for more in-depth tech sections.

As discussed in the DDBox tech page, DD woofers are built specifically for duty in the DDBox system, the woofers and boxes were developed together to extract the highest efficiency from a given box volume.

Don’t start the process with a predetermined idea of what sub size is best, just because your cousin heard a system when he was on vacation at his Uncle Lewey’s house and caught a ride with a guy who heard a system once that blew the rear tire off a car with a 6×9 in a cigar box, doesn’t mean 6x9s are the only speaker to design your system around (not cigar boxes).

Let the size and shape of the box determine the quantity and size of the subs.

Step 1: Measuring for the Box

You will need to determine where in the car you can put the subwoofer enclosure and the general amount of space you are willing to give up for the enclosure. Everyone hauls around different stuff, and your type of stuff should be taken into consideration as the system is layed out.

Once you have picked the perfect sub spot, you’ll need to determine the height(H), width(W) and depth(D) of the available space. These three dimensions will determine what sub possibilities can be used.

If you measured out a box, say, 13 high, 32 wide and 10 inches deep, you can pretty much rule out the use of 18″ and 15″ subwoofers. This is known as the Karloffsenson Paradox, the famous Swedish engineer who determined the optimum meatball size for a given cooking pot while desiring a much larger meatball, he went on to invent meatloaf and his paradox subsequently goes pretty much unnoticed. But, the points still remain that once you define your space, the subs geometry must fit the box and bigger woofers don’t make bigger sound if the box volume is not correct.

Now, in the self-important minority of the world, we use a measuring system based on an old dude’s foot, divided into 12 equal pieces, called inches, because it didn’t make sense to divide things by 10. It was decided to then further chop these inches in half, and half again, and half again until the numbers get uncomfortably large, or small, however you look at it. This is known as the Imperial System, implying a very important foot was measured and worthy then of unquestioning blind support for centuries to come.

If you are from the self-important majority of the world, you might be using a measuring system developed in France, if you really need more reason to stick with dividing some guys foot into fractions of pieces……, if not, then you’ve decided to measure in metres divided my millies and orders of magnitude therein. To convert the superior imperial measurements to Vulcan like metrics, multiply inches by 2.54 for centimeters and for cubic feet, 28.3 liters per cubic foot.

Step 2: Calculate the Airspace

Space is a three dimensional thing, so we need three dimensions H x W x D, multiplied to calculate volume.

Step 2.1: 

We want to know the airspace inside of the box, because that is the amount of air that will be connected to the subwoofers. The box will be made out of some kind of structural material, commonly from wood because it is a renewable resource and we are environmentally responsible. It is also a fairly cheap resource due to many governmental subsidies and controversial forestry regulations which are responsible for all the forests of neatly rowed trees making trekking life easier on all the furry animals.

We must un-calculate the wall thickness from the outer dimensions, 3/4″( or three quarters of an inch for the metric thinkers. The little dash dashes are the symbol for an inch, not misplaced accent marks to make the pronunciation of the vowel A into a different A sound. To make the math easier on a calculator, we convert the fractions of an inch to a decimal equivalent, the true superiority of the Imperial system starts to show, dividing 3 by 4 to get — 0.75″) wood being the most common thickness for enclosures. Our above box, 13H x 32W x 10D would need 1.5″ taken out per dimension, leaving 11.5H x 30.5W x 8.5D, representing the dimensions of the airspace residing in the enclosure.

We now multiply, 11.5″ x 30.5″ x 8.5″ = 2,981.375, to come up with cubic inches.

Step 2.2:

We want to convert cubic inches to cubic feet because this lets us use a smaller number, and smaller numbers are easier to use. A cubic foot, as defined by the Mendenhall Order in 1893, is 12″H x 12″W x 12″D.

Multiplying, 12″x12″x12″= 1728 cubic inches, which is the number of coinhabiting cubic inches that reside inside a box with aforementioned dimensions. If you are an advocate or begrudging user of the Imperial system, this 1728 number is worth remembering. It gets used a lot.

Now, divide our inner box volume by 1728 to gain the cubic foot equivalent;

2981.375/1728=1.72533275. Remember, accuracy to 8 decimal places is excruciatingly unnecessary, 2 places will do nicely. If there are metric guys still following along, you can use all 8 if you want to.

Our box has 1.73 cubic feet of airspace residing inside the enclosure walls.

Step 3: Converting Gross to Net Volume After Speaker and Port Displacements

Net volume is the amount of airspace after subtracting the volume of air occupied by the woofer and port. This is the amount of airspace with which the port is calculated. How is this done without knowing the volume of the port and sub(s)? Is this another, which came first, the chicken or the egg? It is, unlike estimating the timing sequence of evolutionary or whimsical spontaneous creation, we can estimate occupied volumes based on many cases of fixed calculations and come up with a pretty close percentage.

The occupied volume of the port and woofer, for 40Hz tuning and 35Hz tuning, are approximately 18% and 23% respectively. The larger 23% number for 35Hz tuning representing the longer port length for lower tuning, the longer port takes up more of the inner volume.

Multiplying the numbers from our box:
For 40 Hz tuning, 1.73cuft x 0.82 = 1.42 cubic feet of net volume.
For 35 Hz tuning: 1.73cuft x .77 = 1.33 cubic feet of net volume

Port area for a DDBox is 16″ of port area, per cubic foot. See “Why Go Ported”.

Using the 40 Hz tuning example, 1.42cuft x 16″ = 22.72 square inches of port area

Keep in mind that a 10% variation in port area will not be audible so there is a tolerance of plus or minus 2 square inches.

Step 4: Port Length

The sound of the system is somewhat tunable via changes to the port length. As we learned in the Why Go Ported section, the port area needs to be in proper ratio to the cone area, so the DDBox system uses variations to the port length as primary means of tuning frequency mods.

Refer to the DDBox site chart to 23″ long. This will enable a DDBox/sub combo to have effective bass response in the car, down into the low 30s. The DDBox plays all types of music very well and is a perfect tune to begin advanced dial in of your system after the subs break in.

The “break-in” period refers to the time it takes for the speaker’s spiders to loosen up, allowing more excursion. We build speakers with very strong suspensions so they can be enjoyed for years, as they loosen, the bass will become deeper and louder.

After the break-in, the tuning frequency can be lowered by adding length to the port, try 4 inch increments. Conversely, the tuning can be raised by shortening the port.

Step 4.1: Variations on tuning

Some users have specific, frequency enhanced, types of music they like to play. Some even like the way body panels, windshields and non-cartilage types of body parts flex to the beat, some cars offer a complete beat down to those occupants. These applications might skip straight to a longer port length, adding 6 inches to the tuning frequency charts. Some upper frequency response in the 60-80Hz range may be affected.

This added port length also works well for applications where there is poor acoustic loading in the vehicle, or in open room applications like DJ systems and home applications. The increased port mass helps to enhance the low frequency extension.

Some users would like to cut down on box volume knowing their DD system exceeds their dynamic range expectations. The port area can be reduced by 25%, to 12 square inches per cubic foot and using the lower range of DDBox sizes for a given subwoofer diameter. There is a slight sacrifice in maximum output but some very compact designs can sound amazing if calculated correctly.


How to Build a Ported Sub Enclosure

Items you will need

  • MDF board (3/4 inch)

  • Circular or table saw

  • Wood screws

  • Drill

  • Jig saw

  • Terminal cup

  • Port tube

  • Box carpet

  • Carpenter's wood glue

  • Silicone caulk

  • Glue gun

A ported subwoofer enclosure has one attribute that sets it apart from other types of sub enclosures--volume. The design ensures you'll hear lots of strong, low bass when you crank up your system. The size of a ported sub enclosure varies, depending on the size of the speaker. Follow these guidelines to build a sub-enclosure that'll bring out the bass.

Determine the size of your ported sub enclosure. Every subwoofer requires a specific volume of air (box size) for proper operation. Follow the requirements for the diameter and length of the port tube used in your ported sub-enclosure. Note the volume requirement. Draw a few designs for your box, taking into account the amount of space in your car and the size of the sub. Multiply the length, width and height of the enclosure in inches, then divide the resulth by 1,728. This will be the volume, in cubic feet, of your box. Modify the dimensions, if necessary, to come up with a figure that matches the sub's specifications.

Cut out panels for the front, back, bottom and rear of the box using a circular or table saw. Use 3/4-inch medium density fiberboard (MDF)--it's strong and vibration resistant. In the front panel, cut out an opening for your sub using a drill and circular saw. Make sure the sub fits snugly into the opening. In the top panel, cut an opening for the port tube and check the size. Using wood glue and wood screws, put the panels together.

Use your circular or table saw to cut two end panels for the box. In one panel, make an opening for your terminal cup. Mount the end panels to the box, using wood screws and glue. Seal all the joints with silicone sealant to ensure a tight, leak-free box.

You may put box carpet on the box--use your glue gun to attach the pieces.

Put your port tube into the opening on the top of the box, holding it in place with glue. Now screw the terminal cup in place with wood screws. Connect a piece of speaker wire from the back to the terminal cup to the terminals of the subwoofer. Put the subwoofer into the opening and secure it in place with wood screws.

Writer Bio

Based in Virginia, Nichole Liandi has been a freelance writer since 2005. Her articles have appeared on various print and online publications. Liandi has traveled extensively in Europe and East Asia and incorporates her experiences into her articles. She holds a Bachelor of Arts in history from West Virginia University.

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Building and Designing Enclosures

Building the Enclosure

When building an enclosure, the enclosure's walls should be as rigid as possible. Any flexing in the enclosure will drastically decrease your speakers' performance. Also, all of the joints and walls in a speaker enclosure should be airtight, including screw holes and wire holes. Any leaks or flexing will cause cancellation, resulting in reduced output.

Enclosures should be built with very dense and heavy wood. We recommend MDF (medium density fiberboard) or Medite (high density fiberboard), They are rigid, heavy and not porous like some particle boards. We recommend 3/4" (19mm) MDF although 1/2" (12.5mm) MDF is acceptable for woofers 8" and smaller.

Most enclosures are built for multiple drivers and require separate chambers for each driver. Dividers are a very important part of box building because they create strength in the box and provide an airtight seal between the speakers. Keep in mind that no two things are created equally (even speakers of the same size and model!), This will cause drivers in an open chamber to react differently, substantially reducing output and power handling. When assembling the box it is very important to glue all joints. Screws or staples should be placed approximately every 4" (10cm). Drywall screws work better if they are counter-sunk. Countersinking makes it easy to fill over the screw heads for paint or carpet, and improves the appearance of the enclosure.


A quality air stapler has been proven to be a good substitute for counter-sunk drywall screws. Use 1-1/2" (38mm) or 1-5/8" (41mm) staples at least every 3" (7.5cm) along every seam. Don't forget the wood glue. This is much faster and smoother than using screws.

Glue joints all the way across the wall to provide an airtight seal. We recommend Titebond or Elmer's Wood Glue.

It is always a good idea to use corner braces, also called glue blocks, on each joint in an enclosure. Corner braces are usually made from left-over enclosure wood and measure approximately 1" (2.5cm) wide. The braces should be glued and screwed or stapled to the walls and caulked on both edges where they meet the walls. Use a silicone caulk to ensure the airtight seal. Don't use "bathroom tile" type caulk, it won't do the job!

Not all corner braces will be the length of the wall they're attached to. For example, if a wall's length is 36" (1 m), but there is already a corner brace on the adjacent wall, we'd need to deduct one inch (2.5cm) so that the braces fit together - not overlap. Deduct two inches (5cm) from a brace's length if there are braces on both adjacent walls.

When adding braces to an enclosure always add the displacement of the extra wood to the gross box volume as it is designed.


Another type of brace, called a cross brace, should be used in any span that is 12" (30cm) or more to prevent panel vibration. The most common application will be from the front baffle to the rear wall and between the top and bottom walls. This type of brace is usually made of 3/4" x 2" wood. The brace will contact the enclosure only on its ends where it should be glued and screwed or stapled. Place the brace slightly off center for maximum rigidity. A perfectly centered cross brace can actually increase cabinet flex and resonance (at a higher, more audible frequency).

cross braces

Designing General Enclosures

The fundamental Thiele-Small calculations can be performed using a scientific calculator and a little knowledge of algebra. However, it is important to note that the basic calculations have some factors averaged or removed for simplicity, and the answers they give are only approximate. Your best bet is to use known enclosure design data such as given here, or to use a computer program such as LEAP 4.5 along with our published driver specifications to assist you in designing enclosures.

When you have completed your enclosure, it is important to make sure the speaker is at least close to your design specs. Fori 00% certainty that everything is correct, you may want to measure the box tuning frequency for vented enclosures. If you did the calculations by hand or with a simple computer program (any program that requires only Qts, Vas, and Fs for enclosure performance calculations is simple), you will definitely want to measure tuning frequency because the vent dimensions given by the calculations could be off enough to reduce the speaker's performance. Be sure to measure the tuning with the enclosure in the vehicle, the acoustic environment of the speaker can also affect its tuning.

When designing an enclosure, it is best to follow what we call "The Design Sequence." This is a simple, three step process that can save you a lot of time and hair pulling!

The Design Sequence

Step One: Determine size of enclosure.

This is the easy part. Get a tape measure and get in the vehicle. Consult your customer on exactly how much space he or she is willing to forfeit for their system. Measure this area and write down the height, length and width dimensions in inches.

Now we'll learn how to calculate volume for a cabinet from the dimensions we just took. Let's say the space we have available is: 14" High x 41" Long x 14" Wide

The formula for figuring volume is pretty simple. Memorize it now, you'll be using it a lot!

Height x Length x Width = Total Cubic Inches
Total Cubic Inches / 1728 = Total Cubic Feet
Total Cubic Feet / # of Drivers = Total CubicFeet Per Driver

1728 Cubic Inches = One Cubic Foot

What is 1728 and where did that come from? 1728 is one cubic foot or 12 x 12 x 12. Dividing by this figure converts total cubic Inches into total cubic feet. You'll want to divide total cubic feet by the number of drivers to be installed in the enclo¬sure, usually two, to get the total cubic feet per driver. This is how the manufacturer usually lists specifications.

When calculating an enclosure's volume, you will work with EXTERNAL and INTERNAL dimensions. External dimensions are what you have after measuring the space available in the vehicle. Internal dimensions are what you'll want to go by when selecting a speaker for the enclosure. What's the difference? The thickness of the wood used to build the box. For example, if using 3/4" wood, you'd subtract double the thickness of the wood from each dimension to get internal dimensions.

internal cubic inches example

Let's look at our example again and figure the internal dimensions using 3/ 4" wood.

3/4" + 3/4" = 1.5"
14"-1.5" = 12.5"
41"-1.5" = 39.5"
14"-1.5" = 12.5"

12.5x39.5x12.5 = 6171.88
INTERNAL cubic inches

6171.88/1728 = 3.57
INTERNAL cubic feet

3.57 / 2 drivers = 1.79 cu. ft. per driver

Step Two: Calculating Displacement

brace displacement

Displacement refers to the space used by things inside an enclosure that influence total volume and is mostly associated with the drivers in an enclosure. However, other factors will also influence an enclosure's total volume, like ports and bracing. To calculate exact enclosure volume, we'll need to consider port, bracing and speaker displacement.

port displacement

Port Displacement: Calculating the amount of space taken by a port will test your memory of high school Geometry! The formula itself looks pretty simple: Area x Length = Volume. First you'll need to know the port's dimensions. For an example we'll use a 12" long port with a 2" diameter. Now we need to calculate the area of a circle the same size as the port, 2" in this case. (This is where Geometry comes in!) The area of a circle is the radius squared multiplied by "pi" or 3.14". Area of a Circle = r2 x 3.14 The radius of our circle is 1" (half of the diameter). 12x 3.14 = 3.14" Next, we'll multiply this by the port's length, 12". 12" x 3.14" = 37.68 cu. in. So, to get the accurate volume of the enclosure, we'd need to deduct 37.68 cu. in. from the total volume.

Brace Displacement: After figuring port displacement, brace displacement is relatively easy. Braces are discussed in detail a little later so trust us for now. We'll use a 1" x 1" x 20" brace for an example. All we do is multiply the dimensions together (1" x 1" x 20" = 20 cu. in.) and deduct this amount from the cabinet's total volume. Piece of cake! Remember to do this for all braces in the enclosure, there may be quite a few of them!

Driver Displacement: The driver also takes up air space inside the enclosure. If you use Kicker speakers, we've made calculating driver displacement real simple for you, just look at the chart on appendix page 25. The recommended enclosure volumes we give in the charts already have driver displacement deducted. If you use our speakers and go by that chart, you won't have to figure driver displacement. Let's get back to our example again. We currently havel .79 cu. ft. per driver before displacement. This size box might work for a 12" driver or a 10" driver. Let's calculate driver displacement now to where we are.

12" driver displacement = 0.0538 cu. ft. 1.79 - 0.0538 = 1.736 cu. ft. per 12" driver
10" driver displacement = 0.0334 cu. ft. 1.79 - 0.0334 = 1.757 cu. ft. per 10" driver

Now we'll look at braces. Two different types of braces are corner braces and cross braces. For this example, we are building a sealed enclosure in a simple rectangular box. We'll have twelve corner braces (one for each joint), and six cross braces (one for each wall).

We have eight corner braces that are 1"x 1"x 12.5". Each one uses 12.5" cu. in. of our enclosure's total volume, so eight of them use: 8 x 12.5" = 100 cu. in.

Four of our corner braces are 1" x 1" x 37.5". We deducted two inches from the length so the braces would meet instead of overlap the other corner braces. Each one of these use 37.5" cu. in. of our volume, so multiply this figure by four=4x 37.5" = 150 cu. in.

So all bracing combined uses 250 cu. in. Now we'll divide by 1728 to convert to cubic feet.

250 cu. in. / 1728 = 0.0289 cu. ft.

Now we go back to the enclosure volume figures we got after figuring driver displacement and deduct brace displacement:

12" driver 1.736 - 0.0289 = 1.7071 cu. ft.
10" driver 1.757 - 0.0289 = 1.7281 cu. ft.

Result - we use 12" Kicker Competition woofers in a sealed enclosure! Another possibility though, is the 10" Freeair driver in a ported enclosure. It can be quite a long process to figure all these different things, but trust us, going through all the trouble is worth it when you get done and have an enclosure that sounds awesome!

Let's say you're measuring a customer's vehicle for available space and it's basically unlimited in one direction. If two dimensions are known and the other is unset, we have another way to calculate volume for a specific speaker. For example, we'll say the customer wants to use our Competition 12" driver. We know that the recommended enclosure volume for a C-12 is 1.75 cu. ft., so for two it's 3.50 cu. ft. Our two known dimensions are 39.5" and 12.5" (internal). First we'll find the total cubic inches on our two known figures, just multiply them together.

39.5" x 12.5" = 493.75"

Next we need to figure the total cubic inches needed for two C-12's. All we do is multiply 3.50 cu. ft. (recommended for two C-12's) by 1728 to convert to inches.

Now we divide the total cubic inches needed (6048) by the cubic inches that we have already (493.75) to determine the missing dimension.

6048 / 493.75" = 12.25 inches for the width

To check this, multiply all three figures:

39.5" x 12.5" x 12.25" = 6048.44 cu. in.

6048.44 / 1728 = 3.50 cu. ft.

Angled Enclosures

To figure enclosure volume on angled boxes, draw a diagram of your enclosure. It will help a lot to visualize what you're doing.

Using Figure A

Angled Enclosures figure A

fig. A

17" High x 54" Long x 5" Top and 13" Bottom

Since the formula to determine enclosure volume does not allow for two different width dimensions (5" Top and 13" Bottom), we must find an average of these two figures.

To find the average, add the figures together (5 + 13) then divide by the number of figures added (2).

5"+ 13" = 18" 18"/2 = 9"

In essence, averaging the 5" width and 13" width gives us a rectangular box to work with instead of an angled one (note the "dotted line" enclosure). Now the formula for figuring volume works.

3.53 / 2 = 1.765 cu. ft per driver

To calculate internal volume, you must subtract the thickness of the wood. We're using 3/4" MDF again, so deduct 1.5" from each dimension.

54" - 1.5" = 52.5"
9"-1.5" = 7.5"
17"-1.5" = 15.5"
52.5" x 7.5" x 15.5" = 6103.13 cu. in.
6103.13 71728 = 3.53 cu. ft

Angled Enclosures With Risers

Angled Enclosures With Risers figure B

fig. B

This type of enclosure (fig. B) is a little more difficult to work with than just an angled enclosure, but we'll help you through. Follow the calculations below for volume on an angled enclosure with a riser.

Using Figure C.

Dimensions: 17" High x 44" Long x 5" Wide (Top) and 13" Wide (Bottom) with a 4" riser.

First, make the box into a rectangle like we did before by averaging the top and bottom width measurements:

5 + 13=18 18/2 = 9

Instead of using the entire height dimension, deduct the height of the riser, 4" for this example.

17" - 4" = 13" High

So the external dimensions for the first part are (fig. C):

13" High x 44" Long x 9" Wide

Angled Enclosures With Risers figure C

fig. C

We'll go ahead and figure the volume of this enclosure (using internal dimensions). Subtract only one thickness of wood from this height.

12.25 x 42.5 x 7.5 = 3904.68 cu. in.
3904.68 / 1728 = 2.25 cu. ft.
2.26 cu. ft. 12 = 1.13 cu. ft. per driver

Notice that there is a 4"x44"x13" enclosure left over. This is just another airspace that we'll figure volume for and add to the first part. (Use internal dimensions!) Again, subtract only one thickness of wood from this height.

3.25 x 42.5 x 11.5 = 1588.43 cu. in.
1588.43 / 1728 = 0.92 cu. ft.
0.92 cu. ft. / 2 = 0.46 cu. ft. per driver

Now, add 0.46 cu. ft. to the first figure:
0.46 + 1.13 = 1.59 cu. ft. total per driver This is your net internal airspace for each side of this enclosure.

More Info.

Box Building Hints

internal bracing

All the cubic feet numbers given in the supplied charts include the displacement of the woofer. For the ported boxes, the displacement of the port must be added to the final design. It will be impractical to use round ports for these designs. The rectangular port information given will yield the best results.

Always use 3/4" or thicker MDF and make sure all the joints are secure and well sealed. The peak pressure in a ported box can exceed that of a sealed enclosure. All of these designs need some internal bracing. Be sure to add 2"x2" to 3"x3" triangle braces between each of the larger unsupported panels. Kicker recommends using a good grade of wood glue and silicone sealer for an airtight box.

Note:If you prefer an ultra-smooth bass response, you should loosely fill your ported Solo-Baric Enclosure with polyfil. If you do so, the entrance to the port (inside the box) must be covered with hardware cloth, chicken wire, or expanded metal to prevent the polyfil from being blown out through the port. Use of polyfil will slightly decrease efficiency, but will deepen and extend low bass response.


Do not install a ported box with the port against a solid surface. The port opening must remain unobstructed. Use the smallest dimension of the rectangular port as the minimum amount of space required between the port and any surface to insure unrestricted airflow.

Do not install a ported box with the port against a solid surface

If you would like to use a vented enclosure, but the box designs we provide you with (in this manual) do not fit because of width or depth, the designs can be modified. The shape of the enclosure is not vital, but The Volume Is. The volume, of the design you choose, must stay the same. The following diagrams provide you with some help to insure your enclosure is built correctly.


vented enclosure


vented enclosure

If you are going to bend the port at 90° you will need to add 1/2 of the ports height to the length! See Below.

port fig 1 and 2

(Fig. 1)
Hport = 3"
Wport= 10"
Lport = 20"

(Fig. 2)
Since Hport is 3" you need to add 1.5"( 1/2 Of Hport) tO Lport. This means that L1 + L2 = 21.5".

Always measure L1 and L2 down the center to get an accurate measurement!

Here are a couple more examples of the different shape enclosures you can build. The woofer can be mounted on the same side as the port or the back side of the enclosure can be slanted to fit up against your back seat.. On the cut sheets we provide, change the dimensions to accommodate the woofer and the vent on the same side. Make sure the internal volume does not change!

different shape enclosures you can build

More Info.

Conversion Chart

Sometimes an installer needs to calculate the volume of some geometric shape or units of measure. Below are some formulas that should help out.

Triangle Area = 0.5x (Base) x (Height)
Circle Area = (Radius) x (Radius) x 3.1415
Circle Area = (Radius) x (Radius) x 3.1415
1 inch = 25.4 mm
1 mm = 0.0394 inches
1 liter = 0.0353 cubic feet
1 cubic foot = 28.32 liters
1 gallon = 0.134 cubic feet
1 cubic foot = 7.48 gallons
1 cubic foot = 1728 cubic inches
1 cubic inch = 0.00433 cubic feet

Volume (Cubic inches) = (Length) x (Width) x (Height)

milli = 0.001 micro= 0.000001 kilo = 1000 Mega = 1,000,000

Port Diameter

Inside Area

Outside Area (1/4 in walls)

Outside Area

1 in

0.785 sq in

1.767 sq in

0.89 x 0.89 in

1.5 in

1.767 sq in

3.142 sq in

1.33 x 1.33 in

2 in

3.142 sq in

4.909 sq in

1.77 x 1.77 in

3 in

7.069 sq in

9.621 sq in

2.66 x 2.66 in

4 in

12.566 sq in

15.904 sq in

3.54 x 3.54 in

5 in

19.635 sq in

27.758 sq in

4.43 x 4.43 in

6 in

28.274 sq in

33.183 sq in

5.32 x 5.32 in

8 in

50.265 sq in

56.745 sq in

7.09 x 7.09 in

More info:


Subwoofer Box

What is the Subwoofer Box for?

Everyone understands that the box is an indispensable part for the proper operation of the low-frequency speaker, which is designed to work in a certain volume, without it, the subwoofer speaker will simply chase the air, while the efficiency will decrease several tens of times.

Without a box, due to the lack of the necessary damper, the speaker is very easy to pull out of the stroke, this is when the coil starts to come out of the magnetic gap, it is at this point that any slight distortion of the diffuser can lead to a coil's impact on the core (cylindrical magnetic core in the center of the coil), which leads to the detachment of the winding from the coil frame.

Of course there are exceptions, for example, as Free Air subwoofers, which are designed to work in an open volume, but the efficiency of these subwoofers is very small, it is recommended to install them only as a last resort.

Start Subwoofer Box Design

Build subwoofer to box a with port how

Listen, John, I said, there are no women on the Nightmare, why not open a brothel with elven cows for the colonists. Plans for a profitable institution arose in my head as an economist who had gone to school. Bottle John just grunted. - I'm late, boy. Such a brothel already exists, Mikhas Khokhol keeps it, but I can't say that he got rich on this business.


He's been here for a long time, I just haven't used it for a while," explained the mother and began to wash the pear from the outside with. Tap waterthen poured water into a mug, sucked a little liquid out of it into a spray can, and then squeezed the water out, thus rinsing the enema from the inside.Mom, and you didn't give me an enema before, did you.

"daughter, you probably don't remember, because you were still little. I didnt do it, because it seemed to me that you poop normally, but, as the recent incident with your tummy showed, its not.

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Van Vanich, maybe two minutes will be enough?", Nastya whimpered. Bargaining is inappropriate here. " Nastya didn't say anything else, just cried, and tears flowed down her cheeks like a thin stream. Deep down I felt sorry for the girl, but I understood that it was better not to show this and be strict to the end, because otherwise the.

Enema might not give what I wanted The result.

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