As you know, a subwoofer in a car is an integral element for obtaining high-quality, rich and powerful sound. Moreover, in addition to the speaker for the subwoofer, the most important part is the box for the subwoofer.
The sound quality, volume, as well as the ability of the subwoofer to fully “open up”, etc. will depend on the box. In this article we will look at what to pay attention to when designing, as well as how to make a subwoofer box yourself.
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Purpose, design and principle of operation of the CV box
The design of the HF box is aimed at modulating the sound flow. The effect of sound transmission and reflection is used. Thanks to the special housing design, sound harmonization is achieved. This is especially noticeable at low frequencies and when installing a subwoofer. With the appropriate dimensions, the HF box will make the bass sound quite loud, bright, but unusually deep.
Subwoofer box
Purpose and use
In a certain context, this device can be compared to an analog-type sound processor. Now that the purpose is clear, let’s now look at the design, operating principle and calculations. The proposed solution is especially in demand among motorists who want to install high-quality sound on used cars; with some effort, it will not be inferior to expensive audio systems.
So, in the technical understanding, the FM box, as implied by the name, is a resonator. We are talking about a hollow structure with the help of which sounds of a given frequency are reproduced. One of the functions of the resonator is to enhance audio sound. Such a device in the car will allow you to listen to loud music, provide musical accompaniment in nature, or use it for commercial purposes, for example, for scoring weddings and celebrations. The most popular solution is a box for a 12-inch speaker.
Operating principle
Motorists may be familiar with a resonator, another example of which is the CV box For example, it is used as a functional element of a muffler. In this case, the hollow structure has its own characteristics and another purpose.
From a technical point of view, a resonator is an oscillatory system that accumulates vibrations due to frequency resonance. Typically, the design involves “working” with a limited set of frequency characteristics. Depending on the design, resonators of cumulative and instantaneous action differ.
Homemade wooden box
The storage resonator accumulates external energy by reducing the frequency of internal oscillations. In a mathematical context, any resonator design whose oscillation frequency is greater than the oscillation frequency of the external influence is cumulative. This happens whether the diameter is 10 or 12 inches, but you need to choose a different volume.
Instantaneous action implies the correspondence of the internal oscillatory force in period to external oscillations. Such resonators increase the sound power due to thermal absorption of the surrounding space, shifting the frequency at the input power - changes due to an increase in the playback interval.
The common CV box has a rectangular shape with partitions resembling a caterpillar in arrangement. The appearance will depend on the speaker and its features, size – 10″ or 12 inches. At the moment, you can find drawing diagrams for any frequency device and make a resonator at no extra cost. It will differ slightly from the brand name.
You can make a resonator in a mini version. This solution is shown in the figure.
Drawing of a CV box for 12″
To obtain drawings of 10, 12 and 15″ HF boxes, you can use a search engine or our resonator database or calculation program. The easiest way is to search by type of speaker and required volume. For example, a 12″ CV box can be implemented in several versions, depending on the technical features described and demonstrated below.
How to calculate a resonator for the Urals yourself?
First of all, we note that the main material for making this audio device is multi-layer moisture-resistant plywood. The speaker input is sized according to the selected model. The volume and design will depend on the technical tasks: interior features, required power and other features.
Designs depending on the direction of the port
The figure shows that the direction of the port and other parameters also influence the design. Sometimes drivers, after making calculations, are concerned that the dimensions are very large compared to the available space in the cabin, so they recommend a design that is suitable for this task.
Other housing options
The photo shows an example of the calculation of the HF box, but in total the cross-sectional area of the tunnel is taken into account (for example, 10″ or 12″), depending on the caliber of the subwoofer, for example, Machete m10d2.
Example
Use the Quarter Wave Box calculation program. You will only need to enter the speaker parameters and box volume. Otherwise you will have to make the drawings yourself.
To do this, use ready-made recommendations - a table with subwoofer sizes for 10, 12 inches and others. The cells show the volume that needs to be taken as a basis to achieve certain audio parameters. A “tuning” is also selected depending on the machine owner’s preferences and frequency. The box can be designed for two or more speakers, they can be different 10″ or 15″.
The proposed variations demonstrate some solutions for organizing a car interior media system that are available for self-production. With a little effort, you will get a high-quality sound system in your car for your new Machete m10d2 or Ural, taking into account the features of your interior and preferences.
How to make a subwoofer box correctly
Types of CV
Above we analyzed the calculation for a quarter-wave of constant cross-section, but there are also tapering and expanding tunnels.
If sound quality comes first for you, then make a HF with a tapering design. It is larger and more complex to manufacture, but the result is a bass that is accurate, fast and deep. This case is suitable for systems focused on sound quality! Unlike the classic direct HF port, the port is made to gradually taper from 3 Sd to 1.5 Sd at the outlet.
The expanding port will give the highest efficiency and loudness due to the humpback frequency response.
A tapering port will be shorter than the opening for the same setting. See the table for calculated data:
Port length depending on the type of CV
Cutting parts
So, you have decided on the shape for the sub box and you have a drawing.
Mark the sheet according to the parts and cut according to the marked dimensions. Use a disk with a large number of teeth; the smaller the tooth size of a circular saw blade, the fewer chips you will get, and their size will be insignificant.
If you use a manual circular saw and your hand is not full, it is better to use a guide so as not to accidentally “fill up” the cut.
It is better to do this work together, since it is quite inconvenient for one person to turn large sheets and hold them while working.
Below is a good video from Rockford Fosgate, albeit in English, but everything is clear here without translation - choosing the shape of the body, lining up the parts, cutting.
Subwoofer enclosure assembly
To properly make a box for a subwoofer, before screwing in a self-tapping screw, drill a hole for it with a thin drill, this will increase the strength of the fastening and protect the plywood from delamination. Distribute the number of screws evenly along the length of the side and make sure that they do not meet at the corners.
Almost always a template for cutting out the mounting hole comes with the sub; it can be part of the box or be a separate attachment. Cut out the template, transfer it to the front side of the box and cut it out with a jigsaw or router.
Template for mounting hole (cut from box)
If you don’t have such a template, you’ll have to arm yourself with a compass. When marking and cutting out the hole for the speaker, be very careful! The basket shelf is almost always narrow. If you cut less than required, the subwoofer basket will not fit into the hole; if you cut a little more or not exactly, the sub will not fit tightly or the mounting screws will hang in the air.
Quarter wave (QW) in simple words
Do not be alarmed by the clutter of these words, we will not delve into the theoretical foundations of the quarter-wave resonator or quarter-wave resonator here, as it is usually called. Let's consider this type of design from the user's point of view, because CV has important advantages and few disadvantages.
In short, a quarter wave is a tunnel of a certain length and cross-sectional area; there are no separate concepts of housing and port, as we are used to in a bass reflex. If there is free space, it is very simple to calculate and does not have any special difficulties in manufacturing.
Main advantages of CV:
- reduced degree of group delay, well-developed bass and detail, sometimes exceeding a closed box;
- wide and smooth frequency range - with the right approach, the upper and lower bass can be easily mastered;
- increased level of efficiency, 20–40% more than that of bass reflexes or bandpasses and 150–300% than that of a closed box.
Just a cheater building - that's how it is! There is only one minus, but a significant one - the large volume of the box.
In other words, if you don’t mind space, then the HF will be the best choice for subwoofer design.
Subwoofer boxes: types and differences
So, having decided on a speaker for the sub (usually 10-12 inch speakers from well-known manufacturers), you can move on to the box. Please note that the design of the subwoofer box determines the volume and sound quality of low frequencies. Simply put, an incorrectly designed box can “strangle” a high-quality and powerful subwoofer woofer.
First of all, it is important to understand that there are several types of subwoofer boxes (subwoofer box, subwoofer box, etc.). To put it simply, we can highlight:
- closed subwoofer housing;
- bandpass;
- bass reflex;
If we consider the bandpass, in this case there may be a bandpass of the 4th or 6th order. In the first case, this type of subwoofer has a housing that is divided into chambers of different volumes. One chamber contains the speaker itself, and the other receives a bass reflex, also known as an air duct. A subwoofer of this type gains the ability to somewhat limit the frequencies reproduced by the diffuser.
A bass reflex is a subwoofer that has a special tube in the housing. This pipe removes air and is also capable of transmitting additional sound coming from the rear of the woofer. The sound of a sub in such a cabinet is “average”, being the middle ground between a closed box and a bandpass.
ChV calculation
The cross-sectional area of the port depends on the size of the speaker.
In words it means that the cross-sectional area of the port is one and a half effective area of the subwoofer.
It is important to know that the effective area (Sd) is not calculated by the standard size (10″, 12″, etc.), it is always smaller since the basket and part of the suspension do not participate in the radiation. Manufacturers often indicate this value in the documentation, but if there is no data, you can use the table:
Effective subwoofer area by size
also calculate Sd
Sd —effective subwoofer area, cm²;
where D is the diameter in centimeters, taken through the center from the middle of the suspension.
For a square subwoofer, calculating the area is even simpler - you need to square the length of one side.
Effective area of subwoofers
Accordingly, the port area is calculated as follows:
— cross-sectional area of the port, cm²;
The CV setting depends on the length of the port and is calculated as follows:
— port length, m.
Fb – desired tuning frequency, Hz
The optimal range is 35–45 Hz, no one forbids setting it low, if you like infra, lower the setting.
Calculation example
For example, let's calculate the frequency response with a setting of 38 Hz for a 12-inch (30 cm) speaker.
S port = 1.5 * 480 (from the table for 12″) = 720 cm²
In order for the box to fit into the car, the port is rolled up.
Subwoofer housing: how to make it yourself
Taking into account the fact that the bandpass is the most difficult to manufacture, this enclosure is difficult to design and calculate the subwoofer box without special skills, knowledge and experience.
On the one hand, you can use the WinlSD program to calculate the subwoofer. This software allows you to select the size, calculate the volume of the subwoofer, and even create a three-dimensional model.
However, on the other hand, such a task is usually beyond the capabilities of an ordinary car owner without special knowledge (you need to know the characteristics of the speaker, take into account a number of additional features, etc.).
This solution (subject to proper design) will be more than enough. The bass reflex makes it possible to play back the lowest frequencies with high quality, provides increased efficiency, etc.
So, first we select the material for making the subwoofer. Typically, multilayer plywood is used for these purposes. You can also take chipboard. These materials are affordable, easy to work with, and provide good sound insulation.
- As an example, consider a subwoofer made of multilayer plywood (3 cm thick). In order to make a box for a subwoofer, you need to prepare, on average, about 100 wood screws 50-55 mm.
You also need to purchase sound insulation, have a drill, a screwdriver or screwdriver, a jigsaw, liquid nails, sealant and PVA glue, about 3 meters of carpet and a terminal block. The next step is the drawings of the subwoofer box.
The calculation of the subwoofer box is individual; the parameters depend on the size of the speaker, etc. Using an example, consider a sub with one 12-inch speaker. The volume of a box for a subwoofer with one such speaker, according to the recommendations of experts, is 45-50 liters.
To calculate the box for the subwoofer, below is an introductory diagram with the dimensions of the panels. If you do not have the skills to do this kind of work, it is recommended that you separately study the materials on how to make a drawing for a subwoofer yourself.
During design, you need to separately ensure that the minimum distance from the walls of the case to the speaker, as well as the volume of the box itself, is calculated exclusively on the inner surface, and not on the outer one.
Let's move on. After preparing all the elements, you can proceed to assembling the subwoofer box. First of all, use a jigsaw to cut out a hole for the speaker. For example, a speaker is 30 cm. Please note that the shortest distance from the center of the diffuser to the wall of the subwoofer is, conditionally, 200 mm. You can measure 230 mm, since 3 cm is the width of the plywood itself.
Now you can assemble the side walls of the case, coating them in the same way with liquid nails and tightening them with self-tapping screws. You also need to cut a hole for the terminal block on the back cover of the case for the subwoofer. Next, all parts of the subwoofer need to be connected, checking the correct dimensions of the structural elements themselves and the quality of fastening.
Box for 12 subwoofers with bass reflex
To build the box we will need:
- Dense multi-layer plywood or chipboard
- Self-tapping screws
- Screwdriver or screwdriver
- PVA glue
- Carpet
- Sound insulation materials
- Wires and terminal block
Cover the inside of the box with sound insulation. Before screwing in the screws, use a thin drill to mark holes so that the plywood does not burst. Assemble the structure, cut out the carpet with a margin to bend along the edges. Apply glue, let dry, and staple.
How to make a stealth subwoofer with your own hands
Having considered how to make a box with your own hands, it should be noted that the owner does not always intend to install a large box in the trunk. For this reason, many car enthusiasts are interested in how to make a stealth subwoofer with their own hands.
It is well known that a stealth subwoofer is practical, does not take up much space and is often a factory solution on cars where a subwoofer is used in the speaker system.
Let us immediately note that making and installing a stealth subwoofer with high quality is more difficult and more expensive than a regular box. If only this option is needed, then for manufacturing and installation you will need:
- woofer;
- grill grate for protection;
- socket for connecting to an amplifier;
- wire for connecting the woofer to the outlet;
- Chipboard or multilayer plywood (thickness 2 cm);
- some fiberboard, epoxy glue, fiberglass;
- wood screws, mounting tape and plastic film;
- tools you need are a screwdriver, a drill, a jigsaw and a brush;
Having decided on the installation location, you need to unload the trunk, remove the trunk trim at the subwoofer installation site in order to be able to install the subwoofer as close as possible to the car fender.
At the initial stage, you need to lay a plastic film on the floor in the trunk to protect the inner lining from epoxy glue and to implement a fastening for screwing the back wall of the sub. Then you will need to cover the inside with tape. The adhesive tape is glued in a couple of layers.
Now you need to cut the fiberglass into small pieces (pieces 20 cm in length and width). Next, these pieces are applied to masking tape, after which they are glued with epoxy glue. It is better to lay fiberglass overlapping, which allows you to get rid of noticeable seams, joints, etc.
Next, the layers of fiberglass are glued to each other, coating each layer with epoxy glue. The main task is to obtain a sheet about 1 cm thick, which will require 4 or 5 layers.
The main task, the shape should be made so as not to interfere with the trunk hinges, that is, the homemade subwoofer should not interfere with the trunk closing. Having removed all the unnecessary parts, all that remains is to cut out the side walls from the chipboard, as well as the top part - the lid. The rounded part can be made from plywood, and no special calculations are required.
The only thing to get a rounded shape is to wet the plywood, bend it as needed, then attach it and wait until it dries completely. All chipboard sheets must be glued with epoxy glue or sealants used, and then tightened with self-tapping screws. As for the fiberglass box, it is also glued with epoxy resin, and after the resin dries, self-tapping screws are used for fastening.
Now all that remains is to take measurements of the front panel, after which it can be cut. Then a hole for the speaker is cut out with a jigsaw. After the panel is ready, it is attached to the body with self-tapping screws.
To do this, bars are placed along the entire inside of the panel (the distance is maintained slightly greater than the thickness of the plywood). For example, 2.5 cm from the edge. This solution will allow you to mount the front part at the top, bottom, left and right. The result is a reliable connection, especially with the round part.
The final step is cutting out a hole for the socket, which is done in the end part. Upon completion, the strength of the structure is assessed. If necessary, you can add more layers of epoxy and fiberglass to the curved part.
This can be done using universal putty. After drying, all that remains is to level the surface with medium and then fine sandpaper, then prime and paint the body.
What's the result?
As you can see, the decision to make a housing for a subwoofer in a car with your own hands will require certain skills and tools. However, if you do everything correctly and use good quality materials, you can get a fairly powerful sub with good sound.
Finally, we note that after connecting the subwoofer, you also need to configure it. Only after proper adjustment and tuning of the subwoofer will the sound “reveal” to its fullest, which will allow you to fully customize the car’s acoustic system in the future.
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After preparing all the tools and materials, work on the construction of the structure can begin. Making a box for a 12-inch subwoofer with a diameter of 30 cm is quite simple. First of all, you should make a hole for the future speaker, maintaining a distance of 20 cm from the center to the walls.
Next you need to follow the following instructions:
- We are preparing the main elements of the future homemade building. Their parameters are calculated in advance on a trusted resource with online calculators.
- We make a hole in the front of the plywood sheet or MDF, chipboard.
- We cut a slot above the hole for the bass reflex tube and screw the compartment.
- We glue the side elements with PVA glue and fasten them with self-tapping screws. It is important to tighten the fasteners all the way, as any voids will negatively affect the sound quality.
- We cut out places for the wires at the back of the case.
- Before connecting all the components, we place the speaker in the box.
- The final stage involves finishing the interior space. Joints and crevices should be sealed with caulk or epoxy to improve sealing.
- External finishing consists of covering the body with carapet fabric. The carapet is stretched and secured with epoxy or a furniture stapler.
After completion of all stages, final assembly is carried out with connection to the standard car radio.
Since the closed bass reflex box (FI) is large in size, car owners prefer to install a compact “Stealth” subwoofer made by themselves. The mini model provides clear sound over a wide range of frequencies and takes up less space in the car.
In most cases, the box for the 10th subwoofer is placed in the trunk, but some people practice mounting it in the fender or spare tire niche.
The optimal volume for uninterrupted and high-quality operation of the device is 18 liters if 12-inch subs are used.
To properly make a box for a subwoofer, you can consider a simplified option by creating a closed box. It is created according to the same principles as the bass reflex model, but without making a gap. The ZYA has a hole for the speaker, so its design looks quite simple.
All kinds of bandpasses represent a full-fledged bass reflex, but in a modified format. Therefore, assembling a homemade sub is quite simple.
The most complex design is considered to be a subwoofer in the form of a horn. Due to the complexity of manufacturing, novice craftsmen abandon this option, preferring more simplified models. However, the horn is distinguished by volumetric lows and provides deep sound at all frequencies. But any deviation from the drawings will make all efforts useless, because... The sub won't sound right.
Therefore, experts recommend choosing the option of a closed box or bass reflex box for the subwoofer. The bandpass is also characterized by its simple design.
When assembling a box for a subwoofer, it is important to follow all safety rules and be careful. The work involves the use of piercing and cutting objects, as well as electric tools. The use of faulty devices is prohibited.
